Wet Rot Research Articles

Exploration of Timber Dry and Wet Rot Defects in Buildings: Types, Causes, Effects and Mitigation Methods

Exploration of Timber Dry and Wet Rot Defects in Buildings: Types, Causes, Effects and Mitigation Methods

First Report of Bulb Rot Disease of Banana Caused by Klebsiella variicola in China.

Banana (Musa spp.) is an economically important fruit and food crop globally as well as in China. In March 2023, a bulb rot disease was observed on more than 20% of cultivated dwarf bananas in a plantation in Wuming County of Guangxi Province, a major hub of banana production in China. Infected plants showed crackles at the basal part of stem and were relatively dwarf, while yellowing of the leaves was not observed. When the rhizomes were cut open, water-soaked lesions with a yellow or black margin can be seen in the bulb. In severe infections, the internal tissue became dry or wet rot, and there was typical dark-brown cavity formation in the bulb. The rot was limited to the bulb. To isolate the causal agent, dissected diseased tissues (5×5 mm) were surface sterilized with 75% ethanol (30 s) and 2% NaClO (3 min), followed by three rinses with sterile water. The sterilized sections were soaked in 2 mL of sterile water and shaken for 5 min in a vortex oscillator. The suspension was streaked on Luria-Bertani (LB) agar medium, and incubated at 28℃ for 24 h. Single colonies were re-streaked three times to obtain purified isolation. Twelve pure bacterial cultures with similar morphology were isolated from three plants taken from the field. The bacterial colonies were yellowish white, mucoid, round, and raised with translucent surfaces on the LB agar plate. Three strains Gxkv1, Gxkv2 and Gxkv3 were selected for further analyses. The 16S rDNA gene (GenBank Accession OR461756, PP094726 and PP109349) were amplified using primer pair 27F/1492R (Frank et al. 2008). Comparing 16S sequences against GenBank showed 99.86%-100% sequence identity to Klebsiella variicola strain (MZ475068) for the three isolates Gxkv1 (1,398/1,398 bp), Gxkv2 (1,398/1,396 bp) and Gxkv3 (1,398/1,398 bp). A multilocus phylogenetic analysis was conducted by neighbor-joining method (1,000 bootstrap values) based on three housekeeping gene sequences of gyrA (GenBank Accession No. OR515493, PP105747, PP105748), rpoB (OR515494, PP105751, PP105752 ) and infB (OR515495, PP105749, PP105750) genes which were amplified by gyrA-A/gyrA-C, CM31b/CM7 and infB867F/infB1819R primer sets, respectively (Rosenblueth et al. 2004). The results of phylogenetic analysis showed the three strains belong to the K. variicola clade. A pathogenicity test was conducted on six healthy 3-month-old dwarf banana plants by spraying 10 mL of bacterial suspensions of Gxkv1 (108 CFU/mL) into the rhizome which wounded with a sterilized needle; another six healthy control plants were sprayed with 10 mL of sterile water. Following inoculation, the plants were placed in a greenhouse at 28-32°C. After 30 days, all inoculated plants showed symptoms similar to those observed in the field, while the control plants remained healthy. Bacteria were successfully reisolated from the symptomatic tissues and identified to be K. variicola by PCR mentioned above. K. variicola has been reported to cause rhizome rot of banana in India (Loganathan et al. 2021), and to cause plantain soft rot in Haiti (Fulton et al. 2021). Besides, previous reports from China only showed K. variicola causing banana sheath rot (Fan et al. 2015, Sun et al. 2023). To our knowledge, this is the first report of bulb rot disease of banana caused by K. variicola in Guangxi Province, China. This finding will provide important information for studying the epidemiology and management of this pathogen.

First report of Botrytis cinerea causing gray mold on Prunella vulgaris in Hubei province, China.

Prunella vulgaris L. is a perennial herb plant of the Lamiaceae family, and its dried spicas have been widely used as medicine, health-promoting food or tea around the world. P. vulgaris is distributed all over the world, such as Europe, Asia, northwestern Africa and North America, as well as the Huaihe River Basin and the middle and lower Yangtze River Basin in China. In February 2022, a serious disease like gray mold occurred in planting fields of P. vulgaris in Wuhan, Hubei (N30°27'07″, E114°15'49″), causing approximately 20% of plants were diseased in the field. Early symptoms were characterized by small, round gray-brown lesions on the leaves of P. vulgaris. Later, a large number of stems and leaves are wilted or necrotic, associated with wet rot and waterlogged spots and covered with light gray or grayish white flocculent mildew layer. To determine the causal agent of disease, 10 plants with the typical symptoms were collected from fields. The stems and leaves of diseased plants were cut into pieces (2 to 3 mm×5 mm), disinfected with 75% ethanol for 3 minutes, rinsed 3 times with sterile water. Each lesion sample was isolated and purified using separate PDA petri dishes at 25°C, and ultimately all samples yielded morphologically consistent pure strain colonies. From the 10 isolates obtained, XKC-1 was chosen as a representative isolate for further study. XKC-1 colonies showed gray aerial mycelia, which were fast-growing and grew over the whole plate (9 cm) after 4 days. In addition, some black and hard sclerotia (1.88±0.94 mm, n=50) with round or irregular shape developed on the colonies after approximately 10 days of incubation at 25°C (Fig. 2A, B). XKC-1 showed branched conidiophores with enlarged apical cells and numerous conidia (Fig. 2C). Unicellular conidia were colorless or gray, ellipsoid or ovoid, smooth and 7.91-12.38 μm × 10.08-13.82 μm (n=30) in size (Fig. 2D). Based on morphological characteristics, the isolate was initially identified as Botrytis sp. (Ellis 1971). To further identify the species, the genomic DNA of XKC-1 was extracted, and the ITS, LSU and G3PDH genes were amplified with the primers ITS1/ITS4, LROR/LR5 (Zhou et al. 2022) and G3PDH-F/G3PDH-R (Jin et al. 2022), respectively. The results indicated that the ITS (ON090404), LSU (ON090417), and G3PDH (ON169893) sequences were 99.80%, 100% and 99.46% identical to the sequences of Botrytis cinerea Pers. strain (MK370693.1, MN148533.1, MN630267.1), respectively. A phylogenetic tree constructed based on a concatenated sequence (ITS, LSU, G3PDH) using the neighbor-joining method in MEGA7 (Tamura et al. 2013) revealed that XKC-1 grouped with concatenated sequences from three representative B. cinerea isolates in GenBank. Based on the morphological characteristics and molecular identification, the strain XKC-1 was identified as Botrytis cinerea. For pathogenicity tests on detached leaves, 5 mm PDA cakes prepared from XKC-1 were placed on the leaves obtained from healthy P. vulgaris after wounding with a needle (n=10), while PDA medium without mycelia were used as control (25 ± 2°C) (Li et al.2020). Mycelia began to germinate and infect plant tissues at 1 dpi. A large part of the leaves showed water soaked spots covered with mycelia on the surface at 4 dpi. For whole plant inoculations, stem bases of five P. vulgaris seedlings were pierced with sterile needle, and then inoculated with three XKC-1 mycelium PDA cakes. Five plants were inoculated with three PDA cakes without mycelia as a control. After 2-4 days, lesions appeared on the leaves and covered with a gray-white mycelial layer, similar to those observed in the field. However, controls remained symptom free. The pathogen was reisolated from the diseased tissues, the colonies, microscopic characteristics and molecular identification were consistent with those of XKC-1. To our knowledge, this is a first report of B. cinerea causing gray mold on P. vulgaris in Hubei, China. This report would provide resources and reference for controlling of the increased incidence and economic losses of gray mold on P. vulgaris.

Yield and Post-Harvest Pest Status of Some White Yam (Dioscorea rotundata Poir.) Landraces in Uyo Southeastern Nigeria

Field experiment was conducted at National Cereals Research Institute (NCRI),Uyo out- Station in 2012 and 2013 to evaluated yield and post-harvest pest status of some yam landraces in Nigeria. The experiment was laid out in a randomized complete block design (RCBD), replicated thrice. Treatments were eight white yam landraces; Nwopoko, Obiotorugo, Offala, Hambakwashe, Aloshi, Udeanyi, Pepa and Eteme and one improved yam cultivar TDr 89/02665. Data obtained from yield and pest severity were subjected to analysis of variance. Result showed that Hambakwase produced significant tuber yield of 31.10 and 33.01 t/ha in 2012 and 2013, respectively. Obioturugo produced 28.18 and 28.02 t/ha, respectively. Eteme produced the least tuber yield of 16.23 and 15.33 t/ha. Udanyi had significant higher number of rotten tubers per plot at harvest; 2.41 and 2.08 in both years. At 3 months in storage, Offala had significant dry rot of 1.73 and 2.01, followed by 1.61 and 0.91 dry rot tubers per plot, recorded in Aloshi. Number of wet rot tubers per plot as influenced by white yam landraces at 3 months storage varied significantly different (p<0.05). Udanyi had significant higher number of wet tuber rot; 4.30 and 3.22 in 2012 and 2013. Presence of mealy bug infestation were seen Offala, Aloshi,Udanyi and Eteme in 2012. In 2013, Offala, Udanyi, Eteme and TDr 89/02665 had mealy bug infestation. .Among the yam landraces, scale insects were observed in the following; Obioturugo, Hambakwase and Udanyi in 2012 while in 2013, Obioturugo, Udanyi and Eteme had presence of scale insect in tubers at 3 months storage. This study therefore recommended Hambakwase and Nwopok for high tuber yield, less susceptible to rot, beetle and termite attack. Also, these promising yam landraces showed be incorporated into yam breeding programme in Nigeria.

IMPLEMENTATION OF CERTAINTY FACTOR METHOD IN PEST AND DISEASE DIAGNOSIS IN HYDROPONIC PLANTS

Pest and disease attacks often occur in hydroponic plants so that many plants are damaged and result in losses for farmers or crop failure. The problem of pests and plant diseases is the main obstacle in increasing agricultural productivity, these conditions affect farmers' income and the provision of hydroponic plant food. The farmers do not know what types of pests and symptoms of diseases attack plants, making it difficult to handle diseases on hydroponic plants. Likewise for hydroponic plants located at the Agricultural Service of Asahan Regency which are attacked by pests, hydroponic experts say that the appearance of small leaf spots appears on the upper side of the leaves that damage hydroponic plants and because the cause of pests that cause disease in hydroponic plants is unknown, so farmers are hesitant to take countermeasures. An expert system is a computer program designed to make decisions such as decisions taken by an expert or expert. Therefore, an expert system with the Certainty Factor method is made in the diagnosis of pests and diseases in hydroponic plants. The purpose of this study was to apply the certanity factor method to diagnose pests and diseases in hydroponic plants. The results of the pest data test found spider mites with a confidence level of 79% and wet rot disease with a confidence level of 62%. The conclusion obtained is that the certainty factor method can detect early types of pests and diseases on hydroponic plants quickly and accurately.

POTENTIALLY DANGEROUS CAUSES OF BACTERIAL DISEASES OF POTATOES IN UKRAINE

An overview of bacterial causative agents of soft (wet) rot of potatoes is given, the epidemiological and etiological aspects of the diseases caused by them are analyzed. When preparing the article, general scientific methods were used: generalization, comparison, system analysis. Data from the European and Mediterranean Plant Protection Organization (EOPO), as well as data from phytosanitary services of EU countries and Ukraine, scientific literature served as material for the analytical study. Trade in plant materials, including potato seed tubers and ornamental plants, is largely responsible for the widespread distribution of pathogens. Locally, pathogens are also spread through plant debris, soil, waterways, aerosols, alternative hosts, and/or farm machinery. The main causative agents of bacterial wet rot of potatoes are gram-negative bacteria of the genera Pectobacterium and Dickeya and quarantine phytopathogens of the genera Clavibacter and Ralstonia. The main methods of detection and identification in asymptomatic potato tubers on an industrial scale are: phytopathological (visual examination of plantations and registration of symptoms of soft rot), microbiological (cultural-morphological and biochemical method, use of test systems for accelerated identification of microorganisms), immunoenzymatic ( enzyme immunosorbent assay), molecular genetic (PCR with specific primers, BIOLOG, DNA fingerprinting and nucleotide sequencing). To date, there are no completely effective pesticides to control all pathogens, so disease control measures will continue to rely primarily on avoiding infection during plant cultivation, and especially during the production of healthy certified seed. For a crop like potatoes, this is primarily based on obtaining bacteria-free minibulbs, applying strict seed certification schemes and strict phytosanitary restrictions. Knowledge of the sources of pathogens and routes of infection should be the basis for the application of phytosanitary measures, especially during and after harvest. Control of quarantine phytopathogens requires special attention. Soft rot pathogens are the main cause of limiting potato production in many regions of the world, particularly Clavibacter michiganensis subsp. sepedonicum and R. solanacearum are quarantine objects of the A-2 list of the European and Mediterranean Organization for Quarantine and Plant Protection. Upon entering our country, R. solanacearum has a high probability of acclimatization and spread in the country.

English

Amaranthus species is an important leafy vegetable in Ghana; however, foliar diseases of the crop reduce the marketable and edible portions as well as income to farmers. To facilitate the development of disease management strategy, there is the need to document various diseases limiting amaranth production. In view of this, surveys were carried out in forty-three peri-urban vegetable farms in the Kumasi and Tamale Metropolis of Ghana to assess the prevalence and severity of fungal diseases associated with amaranth. Farms were selected using snowball pattern and on each farm, disease incidence and severity were assessed on 45 plants. Disease incidence for any particular fungal disease was calculated as number of plants showing symptoms compared to total number of plants selected whilst disease severity was rated as extent of tissue damage using a severity scale of 1-5. Survey results revealed anthracnose; stems cankers, wilting and wet rot as most prevalent diseases on amaranth. Wilting was the most frequent disease observed; occurring in 95% of farms visited whilst anthracnose, wet rot and stem canker were observed in 91%, 40 and 47% respectively of farms visited. Similarly, wilting disease incidence ranged from 13.3 to 51% across all locations compared to 13.3 to 58.3% for anthracnose, 11.9 to 61.7% for wet rot and 18.3 to 51.7% for stem canker. This work is among few investigations that had been made into diseases affecting the production of Amaranth in Ghana. Key words: Disease symptoms, fungal foliar diseases, incidence, infection, severity

First Report of Soft Rot of Pitahaya Fruit Caused by Gilbertella persicaria in Mexico.

Pitahaya (Hylocereus spp.), also called dragon fruit, is a cultivated cactus that is native to Mexico as well as Central and South America. In September 2021, soft rot of fruit of H. ocamponis, H. undatus, and H. costaricensis was observed in a commercial orchard located in La Cruz de Elota, Sinaloa, Mexico. The disease occurred on approximately 15% of pitahaya fruit. Lesions on fruits were water-soaked and light brown, extending to the whole fruit and covered with mycelia, sporangiophores, and sporangia. Colonies of a fungus were consistently isolated on PDA medium and 10 isolates were obtained. Three isolates were selected and deposited in the Culture Collection of Phytopathogenic Fungi at the Research Center for Food and Development (Culiacán, Sinaloa) under accession nos. CCLF171-CCLF173. Colonies on PDA medium were initially white and later grayish. Sporangiophores were hyaline to light brown, and aseptate. Sporangia (n= 30) were initially light brown but became black at maturity, globose to subglobose, single, terminal, 65.8 to 117.2 µm in diameter, and longitudinally separated into two halves. Columellae (n= 20) were light brown, obovoid, 33.5 to 72.9 × 31.5 to 69.8 µm, with a distinct basal collar. Sporangiospores (n= 100) were hyaline, globose to ellipsoid, aseptate, 6.9 to 12.8 × 5.1 to 10.9 μm, with polar appendages. Chlamydospores were solitary or in chains, oval or irregular. Zygospores were not observed. Based on the morphological characters, the fungal isolates were identified as Gilbertella persicaria (Benny 1991). To confirm the identity, total DNA was extracted, and the internal transcribed spacer (ITS) region was amplified by PCR using the primers ITS5/ITS4 (White et al. 1990), and sequenced. The ITS sequences were deposited in GenBank under the accession nos. OM301904-OM301906. A BLASTn search of these sequences showed 99.47 to 99.81% identity with the sequence MK301174 of G. persicaria from Hylocereus sp. in Taiwan. A phylogenetic analysis based on Maximum Likelihood method grouped the isolates CCLF171-CCLF173 within the G. persicaria clade. Pathogenicity of the three isolates was verified on healthy Hylocereus spp. fruit. Fruit of H. ocamponis, H. undatus, and H. costaricensis were surface sterilized with 80% ethanol, and dried. For each fungal isolate, five detached fruits were superficially wounded with a sterile toothpick and inoculated by placing 15 µL of a spore suspension (1 × 105 sporangiospores/mL). Sterile distilled water was applied to five healthy pitahaya fruits to serve as controls. All fruits were kept in a moist plastic chamber at 25°C and 12 h light/dark for 6 days. All inoculated fruits developed rot 3 days after inoculation, whereas no symptoms were observed on the control fruits. The experiment was repeated twice with similar results. The fungi were consistently re-isolated from the diseased fruits, fulfilling Koch´s postulates. Gilbertella persicaria has been previously reported to cause stem rot, fruit rot, and wet rot in pitahaya (Hylocereus spp.) in Japan (Taba et al. 2011), China (Guo et al. 2012), and Taiwan (Lin et al. 2014), respectively. To our knowledge, this is the first report of G. persicaria causing soft rot of Hylocereus spp. fruit in Mexico. Additional studies are needed to develop effective disease-management strategies.

Lelliottia nimipressuralis (Carter 1945) Brady et al. 2013 as the causative agent of bacterial wetwood disease of common silver fir (Abies alba mill.)

Abstract In recent decades, in many regions of the planet, there has been a widespread deterioration in the health condition and dieback of dark coniferous forests, caused by the combined action of various stress factors of biotic and abiotic origin. Forests with the participation of species of the genus Abies Mill. are particularly prone to degradation and dieback. The aim of the research is to study the symptoms of bacterial wetwood disease of Abies alba in the Ivano-Frankivsk region (state enterprise ‘Kutske forestry’) and to determine the anatomical, morphological and cultural properties of the pathogen. Some of the common symptoms of the disease include cracks and ulcers on the trunks with exfoliated rhytidome and exudate secretion, massive development of epicormic shoots, saturated xylem and phloem, wet rot with a characteristic odour of fermentation and pathological nucleus. Based on the syntaxonomic analysis of fir forests, an attempt has been made to identify the objective causes that lead to excessive development of phytopathogens and dieback of Abies alba. Our research established that the primary cause of dieback of Abies alba Mill. forests is a systemic, vascular–parenchymal disease known as bacterial wetwood of fir, which affects all plant tissues at all stages of ontogenesis. We isolated and experimentally confirmed that the causative agent of the disease is a phytopathogenic bacterium Lelliottia nimipressuralis (Carter 1945) Brady et al. 2013, which also causes bacterial wetwood in many species of forest woody plants, and also studied its common morphological, physiological and biochemical properties.

Postcranial description of Wendiceratops pinhornensis and a taphonomic analysis of the oldest monodominant ceratopsid bonebed.

The early centrosaurine ceratopsid, Wendiceratops pinhornensis, was discovered in Alberta, Canada in a medium density monodominant bonebed from the Oldman Formation (mid-Campanian, ~79 Ma). The bonebed contains abundant, well-preserved, adult-sized and some juvenile-sized postcranial material, allowing for the first description of a number of elements of the postcrania of this basal centrosaurine ceratopsid. The postcranial elements described are generally consistent with postcrania described for more derived centrosaurine taxa. However the rectangular-shaped distal terminus of the ischium previously considered to be an apomorphy of Wendiceratops. is shown to also be present in Medusaceratops, and thus may be a synapomorphy of basal centrsaurines. The bonebed represents a lag deposit within a mudstone-bearing overbank facies and contains individuals from multiple age classes. It contains over 95% ceratopsid remains, with all identifiable elements referable to Wendiceratops. The elements are completely disarticulated, but have undergone little weathering or abrasion (both Stage 0), although the ends of long bones and processes capped by cartilage in life frequently exhibit evidence of wet rot and breakage by hydrological reworking after decomposition. The taphonomy of the bonebed is consist with other monodominant centrosaurine bonebeds that have been interpreted as mass death assemblages preserving evidence of gregarious (herding) behavior. At approximately 79 million years old, the Wendiceratops bonebed is approximately two million years older than other ceratopsid bonebeds indicating that this bonebed is the oldest documented evidence of herding behavior in a ceratopsid.

STUDY OF EFFECTIVITY Bacillus thuringiensis BASED BIO-INSECTICIDE AGAINST Oryctes rhinoceros LARVAE AT SHADE HOUSE

Oryctes rhinoceros is an important pest in oil palm plantations. Adult stage of the beetle causes damage, however larval stage is very important to be controlled to break the cycle of life. An entomopathogenic bacterium Bacillus thuringiensis is one of biological agents to control these insects. Its toxic protein content provides specific insect targets as stomach poison. Objectives of the research was to study the impact of B. thuringiensis propagated in bio-urine enriched with 5 per cent molasses towards Oryctes larvae. The research was carried out in the shade house of Plant Protection Study Program, Faculty of Agriculture, Sriwijaya University from August to November 2021. Experiment was designed in a randomized complete block design with 7 treatments and 4 replications. A total of 20 ml of bio-insecticide was dissolved in 280 ml of water, sprayed evenly on the soil mixed with male palm flowers as feed of larvae. The treatments were 6 isolates of B. thuringiensis isolated from soil in oilpalm plantation, namely with codes: C14, C15, A15, OJ, BK, and LK as well. The results showed density of B. thuringiensis spores in bio-urine media was different in each isolate. The highest spore density in isolate code LK was 4.83 x 1010 spores/ml and the lowest (in isolate A15) was at 3.5 x 1010 spores/ml. Mortality rates were significantly different between isolate treatments starting from day 3 to day 12 of observation. C15 isolate lead the highest mortality rate of 100% on day 12 while other isolates showed mortality data below 100% (88-98%). Body weight and length showed significantly differences on days 0, 6 and 12 after application. Symptoms of infection begin with a change in skin color from white to brown, dark brown and black. Death is characterized by a soft body texture and wet rot.

First Report of Soft Rot Caused by Pectobacterium versatile on Hydrangea macrophylla in China.

Hydrangeas (Hydrangea macrophylla) are recognized for their abundant, showy inflorescences which possess sepal colors (Schreiber et al., 2011). In recent years, the shrubs are grown as potted plants and also for landscaping in China. During the spring of 2021 in seedling greenhouse located in Tonghai County, Yunnan province, China (102°73' N, 24°12' E), a severe bacterial disease was observed on 12-month-old potted plants of cv. Enziandom. Symptoms on Hydrangeas initially appeared as thick liquid produced on the surface of the infected petiole base and water soaking in the infected stems. With the development of the infection, the basal stem color was dark brown and the stem base rapidly turned to wet rot. Severely infected leaves exhibited soft rot symptoms, and the presence of soft rot on mature plants decreased ornamental and market value. This disease was found in 40% of 15 surveyed greenhouses, and the disease incidence ranged from 30 to 50% in different regions. To identify the causal agent, disease-health tissues from infected plants were surface sterilized using 75% ethanol for 30 sec, then soaked in sterile distilled water for three times. The exudate from sheared tissue was streaked onto nutrient agar plates, and plates were incubated at 28°C for 24 hours (Koike et al., 2002). Four representative bacterial isolates BXH21032401-BXH21032404 were selected for further analysis. Colonies on NA were white, small, round and translucent with smooth edges. All bacterial isolates were gram-negative, rod-shaped, with 2-4 circumferential flagella and no entrapment membrane. Physiological and biochemical test and 96 phenotypes screened using the BIOLOG GENIII microplate system (Biolog, Hayward, CA, USA), the test results of four isolated strains are consistent with those of the reported Pectobacterium versatile (Portier et al. 2019). Total genomic DNA was extracted from bacterial suspensions with TIANamp Bacteria DNA Kit (TIANGEN, China). PCR amplification assays were conducted with specially designed primers using extracted genomic DNA as a template. All sequences of the PCR products were deposited in GenBank with accession numbers MZ852237-MZ852240 (16S rRNA), MZ921938-MZ921941 (pmrA), MZ926722-MZ926725 (acnA), MZ926726-MZ926729 (icdA), MZ926730-MZ926733 (gapA), MZ852233-MZ852236 (mdh), MZ926718-MZ926721 (mtlD), MZ921934-MZ921937 (pgi), MZ926734-MZ926737 (proA) and MZ921942-MZ921945 (rpoS). Maximum Likelihood phylogenetic trees based on 16S rRNA, pmrA sequences, and multilocus sequence analysis of housekeeping genes (acnA, icdA, gapA, mdh, mtlD, pgi, proA and rpoS) (Xie et al., 2018), all clustered BXH21032401-BXH21032404 into a clade containing other confirmed strains of P. versatile (Kravchenko et al., 2021). Pathogenicity tests were performed by spraying leaves of healthy 6-month-old potted H. macrophylla (cv. Enziandom) plants with bacterial suspension (20 mL/plant, 108 CFU ml-1). Plants were inoculated with sterile distilled water as control. Soft rot symptoms appeared on inoculated petioles in 5 days after incubation in growth chamber at 28°C showed similar symptoms as observed initially in the greenhouse, and strains were re-isolated successfully from symptomatic hydrangea to complete Koch's postulates. The pathogenicity test was carried out twice. To our knowledge, this is the first time that P. versatile is reported to cause hydrangea soft rot disease in China.

THE EFFECT OF DITYLENCHIASIS INFESTATION OF SEED TUBERS ON POTATO PRODUCTIVITY

In a field experiment to study the harmfulness of potato ditylenchiasis, 15 externally healthy, 15 with weak signs of ditylenchiasis (from 1/10 to 1/5 of the surface of potatoes affected by ditylenchiasis) and 15 with pronounced symptoms of ditylenchiasis (from 1/3 to 1/2 of the surface of potatoes affected by ditylenchiasis) of tubers of the Nadezhda variety were planted. When planting potato tubers severely affected by ditylenchiasis, 40% of the tubers rotted due to their defeat by wet rot. Another 40% of plants showed a slowdown in growth, a decrease in the size of leaves and their chlorosis. After a month, the plants did not differ from those unaffected by ditylenchiasis. In the remaining 20% of plants grown from poorly affected tubers, potato bushes practically did not differ from unaffected plants. In the variant of the experiment with seed tubers slightly affected by ditylenchiasis, the height of the invaded plants on July 1, was on average 25% lower than that of the control plants (on average 51.7 cm). On August 1, the height of plants infested with tuberous nematode was 14 cm lower compared to control plants (on average 72.9 cm). The average number of stems per invaded plant was also less – by 14%, compared with control plants. The mass of tubers in plants grown from tubers affected by ditylenchiasis (490 g) was 29.3% less than that of the control tubers (693 g). The average number of tubers in the control plants (6.7 tubers) was higher than in the invasive plants – by 22.4%. The number of non-standard tubers (38%) in the invaded plants was greater than in plants grown from apparently healthy tubers (26.9%).

First report of Chaetomium pseudocochliodes causing flower rot disease of Camellia reticulata in Yunnan, China.

Camellia reticulata is the world-famous ornamental flower (Wang et al. 2021). In February 2021, the infected flowers of C. reticulata 'Shizitou' were collected in Zixi Mountain, Chuxiong city, Yunnan province, China (24°9'95″ N, 101°42'53″ E). Flower rot disease incidence ranged from 40% to 75% in the garden. The infected flowers showed symptoms of varying degrees of yellow-browning, dry or wet rot to the whole flower wilted and even dropped (Figure 1A, B, C). Three symptomatic flowers were randomly collected in the garden. Tissues from the infected flowers (cut to 5×5 mm size) were surface-disinfected by 75% ethyl alcohol for 30s, rinsed in sterile water for 3 times to air dry, and cultured in Potato Dextrose Agar medium (PDA) at 25℃±2 in the normal light for 5-7 days (Fang, 1998). Similar fungal colonies were isolated from 50%-75% of the infected flowers. Three isolates from different flowers showed similar colony morphology. After sub-culturing of hyphal tips on PDA for 5-7 days, the initially yellow colored colonies showed abundant white aerial mycelium, with sporulation (Figure 1E, F). The asci (Figure 1G) sporulation site is 24(-37) ×7(-14) μm, and the stalk length is 17-42 μm, with 8 biseriate acuminate ascospores. The mature ascospores (Figure 1H) are olive-brown or brown, lemon-like, double-pointed, with slightly umbilical protrusions at both ends, flat on both sides, 9(-11.5) × 7(-9) × 5.5(-7) μm in size, with germ holes on the top (Wang et al. 2016). These morphological features are consistent with Chaetomium pseudocochliodes. The genomic DNA was extracted from the isolated strains. To identified this fungal pathogen genetically, sequence analyses were conducted using the ITS1/ITS4 (Henson et al. 1993), NL1/NL4 (Liu et al. 2011), EF1-938F /EF1-2218R (Tan et al. 2016) primers for the internal transcribed spacer (ITS), large ribosomal subunit (LSU), and elongation factor 1-α (EF1-α) genes. The obtained sequences were deposited in GenBank with accession numbers MZ817067 (ITS), MZ817072 (LSU), MZ820167 (EF1-α). The phylogenetic trees (Figure 2) were constructed to determine the phylogenetic relationships based on MEGA 6.0 maximum likelihood method. In order to confirm the pathogenicity, the tests were conducted with fungus plug (5 mm) from a 7-day-old colony placed onto the surface of healthy petals. The sterile water-absorbent cottons place onto healthy petal surface near fungus plug and plastic wraps cover in petri dish were used for moisturizing. A total of 3 replicates in each of 3 groups were included (3 healthy petals for a group, 1 for wounded inoculation, 1 for unwounded inoculation, and 1 for sterile PDA plug). A sterile PDA plug was placed onto the surface of healthy petals as a control. After incubation at room temperature for 5 days (Ren. 2019), 3 replicates in each of 2 groups of treated healthy petals for wounded inoculation showed obvious symptoms (Figure 1D), and no symptoms appeared in the control, and healthy petals unwounded showed symptoms for 7-10 days. The fungus was re-isolated from the lesions of inoculated tissues. The re-isolated fungal colonies showed identical morphology and high sequence similarity with ITS, LSU and EF-1α of the initial isolate. No fungus was isolated from the controls. The first extraction of C. pseudocochliodes was also obtained from the roots of the Panax notoginseng in Wenshan, Yunnan (Wang et al. 2016). To our knowledge, this is the first report of flower rot caused by C. pseudocochliodes on C. reticulata in China.

Emergence of bacterial soft rot in calla lily caused by Pectobacterium aroidearum in China

Bacterial soft rot is a destructive disease affecting calla lily production, and it is mainly caused by Pectobacterium carotovorum (Pc). In 2019, this destructive disease was observed in the Shandong and Jiangsu Provinces of China and resulted in serious economic losses for commercial greenhouse producers of ornamental plants. The disease symptoms on leaves and stems were yellow and dark brown patches, and then water-soaked lesions that turned to wet rot occurred on the stems. In total, we obtained twenty-eight calla lily soft rot samples collected from Shandong and Jiangsu. Fifteen colonies on LB medium were milky white, nearly round, with a smooth surface and neat edges. The soft rot symptoms in calla lily caused by artificial inoculation were the same as the natural symptoms in the field. Based on the phenotypic properties determined by morphological, biochemical and physiological analyses, 16S ribosomal DNA gene sequence analysis, and multilocus sequence analysis, the pathogen was identified as P. aroidearum. In addition, all P. aroidearum strains exhibited high virulence and a wide host range on monocotyledonous and dicotyledonous plants. This study is the first official report of P. aroidearum causing calla lily soft rot in China, and the results contribute to a better understanding of the disease.

Фитопатологическая экспертиза сортов картофеля в условиях Московской области

Abstract. The aim of the work is to conduct a phytopathological assessment of new domestic potato varieties in the conditions of the Central Region and to identify among them samples that are characterized by a high stable level of resistance to diseases. Methods. The research was carried out at the experimental base “Korenevo” in the Moscow region in 2019–2020. The soil is sod-podzolic sandy loam. The SCC of the growing seasons in 2019 is 1.39 (wet) and in 2020 2.1 (wet). The object of research is 45 varieties of domestic selection from different scientific institutions. All counts were carried out in accordance with standard methods on a natural infectious background. Results. The agrometeological conditions of the growing seasons of 2019 and 2020 contributed to the development of late blight and were satisfactory for the defeat of potato tops by alternariasis. The prevalence of rhizoctoniosis was different – moderate-depressive in 2019 and high in 2020. The lowest incidence over these years was noted only in the Morning variety-1 % (viral diseases). Potato varieties without symptoms of plant damage by rhizoctoniosis – Merchant and Morning, wrinkled mosaic – 19 varieties (41.3 %), twisting of leaves – 32 varieties (69.6 %) were identified. 33 (73.3 %) cultivars showed high resistance (8–9 points) to late blight, and 13 (28.9 %) to alternariasis. The varieties Kupets, Mariinskiy, Prizer, Tret’yakovka, Alyaska, Brusnichka, Kumach, Plamya, Signal, and Utro were distinguished by their complex resistance to these diseases. The autumn tuberous analysis showed that in 21 varieties (46.7 %) tubers were not affected by rhizoctoniosis, 28 (62.2 %) – scab, 11 (24.4 %) – wet rot. On the varieties of Lingonberry, Northern Lights, Signal and Sokur and on the hybrid G-6-14-11 no tubers with defects were found. Scientific novelty. A comprehensive phytopathological assessment of new domestic potato varieties in relation to the conditions of the Moscow region was carried out and samples with plant and tuber resistance to major diseases were identified.

Genetic sources of resistance to root rots chicory

Relevance. One of the significant problems in the technology of obtaining root chicory is the protection of root vegetables from the defeat of root rots. The most common lesions of root vegetables chicory various pathogenic species of fungi causing phomosis (Phoma rostrupii Sacc.), gray rot (Botrytis cinerea (R.) Fr.J), wet bacterial rot (Erwinia carotovora (Jones) Holt.). An important place in solving this problem is the breeding of new varieties that are resistant to major diseases and adapted to the conditions of cultivation in the soil-climatic conditions of the chicory-seeding zone. This requires, first of all, to determine the range of donor varieties of the sign of resistance to root rots, both during the growing of culture, and during long-term storage.Material and methods. In 2018-2020, studies were carried out to assess gene sources of different ecological and geographical origin (including against a provocative background) in the Non-Black Earth Zone of the Russian Federation and to isolate donors of resistance to root rot from them. Research on the Rostov Vegetable experimental station on chicory.Results. Studies have shown that the defeat of root vegetables chicory root rots genetic sources were very different from each other, so Harpachi, Luxor did not affect the. root rots neither on the usual nor on provocative backgrounds.

Influence of fertilizers and of the autumn tillage method on potato yield and phytopathologiс characteristics of tubers

The field experiment on identifying differences in the effect of the herbicide and foliar feeding of plants with liquid nitrogen fertilizer (UAN-32) against the background of autumn tillage with a cultivator or plow on potato yield and phytopathologic characteristics of tubers during storage was carried out in 2019-2020 in the Nizhny Novgorod region. The experiment was laid on sod-podzolic sandy loamy soil in production conditions on two varieties of potato ‒ the super-early Сolomba variety and the medium-early Innovator variety grown for seeds. The variants under study were surface application of the soil herbicide Gezagard in a tank mixture with UAN-32 and foliar feeding of plants with UAN-32 (N42) during the growing season against the background of N42P42K169 (calcium chloride in autumn + ammonium nitrate phosphate in spring). The results indicate that the background fertilization provides the yield of Colombа variety potato of 20.7-29.0 t/ha, the Innovator variety – 17.4-23.1 t/ha. The use of the herbicide is more effective during autumn tillage with a cultivator, providing an increase in yield of 28-37 % on both potato varieties, feeding of plants with UAN-32 contributes to an increase in yield (8-10 %) only on the Сolomba variety. Plowing the soil for potatoes helps to avoid the pest damage of tubers and to reduce their susceptibility to rhizoctonia by 6-27 %, to wet rot ‒ up to 55 %. In general, it has been established that due to autumn plowing with fertilization at a dose of N42P42K169, it is possible to obtain an increase in potato yield exceeding the increase provided both by herbicides and the use of foliar feeding of potatoes.

Pre-Harvest Finger Rot of Cavendish Banana (Musa acuminate) Reported from Moneragala and Badulla Districts, Sri Lanka: Identification and Confirmation of Pathogenicity of the Causal Agent

The present study was conducted to identify and confirm the pathogenicity of the causal agent of a wet finger rot of Cavendish banana, a newly reported pre-harvest disease in commercial plantations in Moneragala and Badulla districts of Sri Lanka. Bacterial species were isolated from banana fingers at three stages of symptom development: initial, middle, and late. Isolated bacterial colonies were inoculated to healthy and mature banana fingers by two methods, namely peel and pulp inoculation, to confirm the pathogenicity by Koch’s postulates. Re-isolated bacterial isolates from inoculated banana fingers showing typical symptoms were identified by biochemical tests and subjected to PCR amplification using universal primers of bacteria, B27F/1492R. Subsequent DNA sequencing of the PCR products and homology search identified the pathogen as a strain of Dickeya dadantii. Phylogenetic analysis with selected Dickeya spp. sequences available in databases identified that the D. dadantii strain of the present study groups with D. dadantii 3937 (CP002038.1), of which the complete genome has been sequenced. Cross infection studies revealed that D. dadantii isolate is more virulent on banana variety Anamalu than on Cavendish banana in terms of days taken to develop the symptoms. The findings identified the causal agent of wet finger rot of banana in the present study as a strain of D. dadantii and confirmed its pathogenicity. The present study was conducted to identify and confirm the pathogenicity of the causal agent of a wet finger rot of Cavendish banana, a newly reported pre-harvest disease in commercial plantations in Moneragala and Badulla districts of Sri Lanka. Bacterial species were isolated from banana fingers at three stages of symptom development: initial, middle, and late. Isolated bacterial colonies were inoculated to healthy and mature banana fingers by two methods, namely peel and pulp inoculation, to confirm the pathogenicity by Koch’s postulates. Re-isolated bacterial isolates from inoculated banana fingers showing typical symptoms were identified by biochemical tests and subjected to PCR amplification using universal primers of bacteria, B27F/1492R. Subsequent DNA sequencing of the PCR products and homology search identified the pathogen as a strain of Dickeya dadantii. Phylogenetic analysis with selected Dickeya spp. sequences available in databases identified that the D. dadantii strain of the present study groups with D. dadantii 3937 (CP002038.1), of which the complete genome has been sequenced. Cross infection studies revealed that D. dadantii isolate is more virulent on banana variety Anamalu than on Cavendish banana in terms of days taken to develop the symptoms. The findings identified the causal agent of wet finger rot of banana in the present study as a strain of D. dadantii and confirmed its pathogenicity.

Бактеріальна гниль томатів за вирощування у закритому грунті

The specific conditions of the protected ground, the almost constant tomato culture without substitution of the substrate, the elevated temperature and humidity lead to the accumulation of a large number of pathogens of bacterial diseases, which limit the increase in yield of this crop. The aim of the work was to characterize the symptoms, determine the etiology of wet rot of tomatoes for growing in protected ground and propose measures to control the pathogen. The study was conducted by standard microbiological and phytopathological methods. The pathogenic properties of the isolates were studied on vegetative tomato plants using a suspension of bacterial cells with a titer of 107 CFU/ml. It was established that the defeat of tomato plants with soft bacterial rot in closed ground conditions prevails in the second half of the growing season. The development of the disease was 30‒34% for a prevalence of 45%. Diseases of tomato plants in greenhouses in the Kiev region of Ukraine are of bacterial origin, caused by the soft rot pathogen P. carotovorum subsp. carotovorum. Characteristic symptoms of wet tomato rot are discoloration, chlorosis and leaf necrosis, void stems, the appearance of depressed water-saturated areas in the stalk, accompanied by decay of the fetus. Effective control measures can be preventive and agricultural measures