Diseased Canes Research Articles

First report of stalk bacterial soft rot of sugarcane caused by Dickeya zeae in China.

In late September 2019, seven stalks of about 1400 stalks of sugarcane cultivar Zhongzhe 1 exhibited soft rot symptoms in a trial plot in Beihai city, Guangxi province of China. Symptoms included scorched and collapsed leaves, maceration of stalks, and sour smelling exudates from the stalks (Supplementary Fig. S1). Severely diseased stalks had collapsed and were dead. Internal stalk fragments of 5 × 5 mm were collected at the junction of healthy and diseased tissue after surface-sterilization of stalks with 70% ethanol for one minute, and three times rinsing with sterile distilled water. Stalk fragments were placed on Luria-Bertani agar medium (1 % w/v tryptone, 0.5 % w/v yeast extract, 1 % w/v NaCl, 1 % w/v agar, pH7.0) and plates were put in an incubator at 30°C for 48h. Four types of bacterial colonies were obtained, and small and white colonies with irregular margins were the most dominant. A single colony of each type was diluted in sterile distilled water and aliquots of each suspension were streaked on fresh medium plates to obtain pure cultures. Ten eight-week-old stalks (11 th leaf stage) of sugarcane plants, which derived from cuttings of symptomless cultivar Zhongzhe 1, were inoculated by injection of 300 μl of bacterial suspension (3.5x108 CFU/ml) into the stalks. Another 10 stalks were injected with pure water and served as control. The inoculated plants were kept in a greenhouse at 25-37℃.Among the four types of bacteria, only strain BH9 induced symptoms that were identical to those of diseased canes observed in the field (Supplementary Fig. S1). Elongated water-soaked lesions were observed around the inoculation sites three days post inoculation. Five of the 10 BH9-inoculated plants had collapsed two days later. Water-soaked stalks had a sour smell similar to the filed diseased plants. Eight days post inoculation, all BH9-inoculated plants exhibited symptoms but control plants remained symptomless up to 30 days after inoculation. Uniform white colonies with irregular margins were isolated from the inoculated stalks that developed soft rot symptom, and these bacteria caused again stalk soft rot symptoms when inoculated to a new batch of 10 healthy plants. The 16S rRNA gene of strain BH9 was amplified by PCR with primer pair fD2/rP1 and the PCR amplicons from three independent colonies were sequenced. The sequences of the three amplicons were identical (Accession No. MT723897). BLAST alignments of the 16S rDNA sequence from BH9 strain with the GenBank database revealed that BH9 belonged to the genus Dickeya (98.5% identity between D. zeae BH9 and D. zeae EC1). Further PCR assays and sequencing of three genes, DNA polymerase III gamma subunit gene dnaX with primers dnaXf/dnaXr, DNA gyrase gene gyrB with primers gyrBf1/gyrBr1, and recombinase A gene recA with primers recAf/recAr, were performed to identify the species within the genus Dickeya (Zhang et al., 2014). BH9 sequences of these genes (Accession No. MT723898 to MT723900) had highest identity (97.5%, 97.6%, and 97.7%, respectively) with those from D. zeae EC1 (GenBank accession No. CP006929.1). To determine the evolutionary relationship of BH9 to other Dickeya species and strains, a phylogenetic analysis was performed using dnaX, gyrB, and recA sequences. As shown in Supplementary Fig. S2, BH9 clustered with D. zeae strains and formed a lineage distinguishable from other Dickeya species. Among the closest strains, D. zeae NCPPB3531 (Accession No. CM001980.1) was isolated from potato and D. zeae CSL RW192 (Accession No. CM001972.1) from river water (Pritchard et al., 2013). Consequently, strain BH9 was identified as D. zeae. This bacterial species has been reported to cause soft rot in rice (Pu et al., 2012), banana (Zhang et al., 2014), maize (Martinez-Cisneros et al., 2014), and clivia (Hu et al., 2018). To the best of our knowledge, this is the first report of a bacterial stalk rot caused by D. Zeae in sugarcane. In fact, low incidence of D. zeae-caused stalk soft rot was recently found in sugarcane fields in Fusui County, about 150 km north to Beihai. Given the potential threat of this disease to the local sugarcane industry, the mode of transmission, cultivar resistance, and measures to control the disease should be investigated.

First Report of Ratoon Stunt of Sugarcane Caused by Leifsonia xyli subsp. xyli in Pakistan.

Sugarcane (Saccharum hybrids), the second largest cash crop of Pakistan, is planted on 1.029 million ha with an annual production of 50 million tons. During a survey of the sugarcane crop in Faisalabad, Sargodha, and the Dera Ghazi Khan Division of the Punjab Province of Pakistan from 2007 to 2010, symptoms consistent with ratoon stunting, including stunted growth and reddening of the vascular bundles at the nodal regions (1), was observed on sugarcane cvs. CP77-400, SPF-241, CP72-2086, and NCo-310. CP72-2086 and NCo-310 showed severely stunted growth in both crop cycles. A chemical test was performed for detecting ratoon stunt from the field. Longitudinal sections of mature nodes were treated with a combination of hydrogen peroxide and hydrochloric acid. Healthy canes developed a blue-green color in the parenchymatous tissue around the fibrovascular bundles, diseased cane did not. This field test illustrated that as much as 25% of the plants were infected by ratoon stunt in the survey area. Aerobic bacteria were isolated from a stunted sample (NCo-310) on modified sugarcane medium (17 g of cornmeal agar, 8 g of peptone from soy meal, 1 g of K2HPO4, 1 g of KH2PO4, 0.2 g of MgSO4·7H2O, 0.5 g of glucose, 1 g of cysteinefree base, 2 g of bovine serum albumin, and 15 mg of bovine hemin chloride) and incubated for 3 to 4 weeks at 28°C. Light, off-white, round, and raised growth bacterial colonies (1.5 to 4.5 × 0.2 to 0.35 μm). Isolates were positive for the gram and catalase reactions and negative for oxidase, aesculin hydrolysis, urease production, and motility. The pathogen was identified as Leifsonia xyli subsp. xyli (formerly Clavibacter xyli subsp. xyli) based on its morphological characteristics (2). A direct antigen coating-ELISA was developed with antiserum raised against L. xyli subsp. xyli at the National Institute for Biotechnology and Genetic Engineering, Faisalabad, Pakistan. Infected or suspected to be infected plants of different cultivars were used for an ELISA test. Results showed that sugarcane cvs. NCo-310 (Log 1.342 CFU/ml) and CP72-2086 (Log 0.118 CFU/ml) had higher L. xyli subsp. xyli titres than the other cultivars tested (SPF-213 [Log 0.071CFU/ml], CPF-237 [Log 0.077CFU/ml], HSF-240 [Log 0.069 CFU/ml], NSG-555 [Log 0.060 CFU/ml], SPSG-26 [Log 0.076 CFU/ml], SPSG-79 [Log 0.074 CFU/ml], SPF-238 [Log 0.057 CFU/ml], and CP77-400 [Log 0.063 CFU/ml]). Cv. SPF-241 (Log 0.107 CFU/ml) was weakly positive for ratoon stunt (4). Axillary buds of sugarcane were injected via a sterile hypodermic syringe with an 18-gauge needle to deliver a bacterial suspension of 109 cells/ml (3). Inoculated sugarcane plants were examined at intervals over 9 months for the development of symptoms and the presence of bacteria. Cultivars were evaluated on the basis of average number of colonized vascular bundles. SPF-213, CPF-237, HSF-240, NSG-555, SPSG-26, SPSG-79, SPF-238, and CP77-400 were resistant; SPF-241 showed moderate resistance and CP72-2086 and NCo-310 were highly susceptible to ratoon stunt. The pathogen was reisolated from the inoculated plants and identified as L. xyli subsp. xyli by bacteriological tests and its serological reaction. To our knowledge, this is the first report of ratoon stunt of sugarcane in Punjab Province of Pakistan.

A Model to Estimate the Amount of Primary Inoculum of Elsinoë ampelina.

In Eastern Canada, anthracnose, caused by the fungus Elsinoë ampelina, is a serious disease on susceptible grape cultivars. In the absence of management tools, anthracnose management relies almost exclusively on fungicide applications programmed at fixed intervals. Therefore, a better understanding of the factors affecting primary inoculum release and abundance would help in the timing of the first fungicide applications. The temporal dynamics of airborne primary inoculum released from cane cankers were investigated from 2007 to 2010. One to three times per week, starting in the first week of April, six 12-cmlong cane pieces were randomly selected from diseased canes that had overwintered on a vineyard floor. The concentration of E. ampelina conidia was expressed as the number of conidia per square millimeter of canker. In total, 27, 32, 33, and 118 samplings were conducted in 2007, 2008, 2009, and 2010, respectively, with the 118 samplings conducted on three sites at 49, 35, and 34 samplings for site 1, 2, and 3, respectively. Each year, the number of conidia per square millimeter of canker was expressed as the proportion of seasonal inoculum (PSI) at the same site and analyzed as a function of degree-days (DD; base temperature = 0°C) accumulated since 1 April (cumulative degreedays [CDD]). The nonlinear sigmoid model in the form PSI = 1.003/(1 + e-((CDD - 566.133)/139.204)) provided adequate fit to the observed data (P < 0.0001, R2 = 0.97). When the model was validated against independent data, the model adequately predicted PSI; however, reliability was improved by adding a "dry days" threshold of 6 days during which accumulation of DD is stopped. This study shows that primary inoculum of grape anthracnose is available early in the season before bud break; meaning that emerging leaves could be infected provided that weather conditions are favorable. The results also show that there is an overlap in the availability of primary and secondary inoculum, mainly during the period of rapid leaf growth, a situation that may explain the explosive nature of the disease. The results suggest that, on susceptible cultivars and when there is a history of anthracnose in the vineyard, a fungicide spray program should be initiated early in the season, as soon as leaves are present.

The Reemergence and Management of Currant Cane Dieback in the Northeastern United States.

Currant cane dieback, caused by the fungus Botryosphaeria ribis (syn. Neofusicoccum ribis), devastated currant production in the northeastern United States approximately a century ago. Later epidemics of this disease were halted by bans on the planting of Ribes spp. to control white pine blister rust, but since regulations restricting the planting of currants were removed in the 1980s and 1990s, currant cane dieback has reemerged in the northeastern United States. In this study, we obtained fungal isolates from diseased canes at four production operations in New York and Connecticut. We confirmed the isolates as N. ribis on the basis of morphology and ribosomal DNA sequence analysis, and verified pathogenicity through inoculation of healthy currant bushes. Furthermore, field trials to study the effects of cultivar, pruning of symptomatic canes, and fungicide applications were conducted over 2 years. Differences in Ribes cultivar susceptibility to N. ribis were demonstrated, with a pink fruiting cultivar (Pink Champagne) having lower levels of dieback compared to two red cultivars (Rovada and Jonkheer van Tets) and one white cultivar (Blanka) evaluated. While there were no consistent reductions in cane dieback incidence over both years and for all cultivars when pruning or fungicide treatments (copper hydroxide and sulfur applications) were used alone, fungicide treatment combined with pruning resulted in significant (P < 0.05) reductions (>80%) in the incidence of dieback compared to bushes not treated with fungicide or pruned.

Soil Solarization as a Component of an Integrated Program for Control of Raspberry Root Rot.

Field and growth chamber studies were conducted during 2000 to 2005 to determine the efficacy of soil solarization for the control of Phytophthora root rot of raspberry (PRR). The exposure time that was lethal to Phytophthora rubi cultures on V8 juice agar plates was evaluated at intervals up to 240 h and at a range of temperatures from 20 to 35°C. Colonies incubated at 20 and 25°C nearly covered the plates in 240 h, while radial growth slowed at 27°C and ceased at temperatures ≥29°C. The exposure times required to kill P. rubi were estimated to be 222 h at 29°C, 168 h at 31°C, 108 h at 33°C, and 52 h at 35°C. Previous exposure to shorter durations at temperature ≥29°C slowed growth of colonies when they later were incubated at 20°C. Field trials were established in 2000 and 2003 at three locations in Washington State to evaluate soil solarization for the management of PRR. Cumulative hours with soil temperatures >29°C at 30 cm soil depth in solarized plots exceeded 200 h in each trial. In the 2000 trial, combinations of solarization, bed shape, and amendments of gypsum were evaluated. Over the 3 years after planting PRR-susceptible raspberry 'Malahat' and 'Willamette', primocane growth and survival were greater (P < 0.05) in raised bed plots that were solarized than in solarized and nonsolarized flat bed plots or hilled bed plots with gypsum. In 2003, trials were initiated to evaluate solarization in combination with applications of mefenoxam and fosetyl-Al. In 2004, solarization increased (P < 0.05) primocane growth of 'Malahat' and 'Qualicum' raspberries at both locations compared to application of fungicides alone and nontreated control plots. At both locations in 2005, density and growth of 'Qualicum' primocanes were greatest in solarized plots, while canes in solarized and fungicide only plots of 'Malahat' were similar. Incidence of diseased canes was lowest in plots that received fungicides. Primocane survival and fruit yields were very low at both locations in the third season because of favorable conditions for PRR and plant stress in late spring. These results indicate that soil solarization can be an effective component of integrated management of PRR in the Pacific Northwest, especially when combined with raised beds and gypsum amendments.

First Report of Diplodia Cane Dieback of Grapevine in Bolivia.

Grape (Vitis vinifera L.) is an important commercial crop in the temperate regions of Bolivia where it has been grown for hundreds of years. In October of 2001, diseased canes of grape (cv. Muscat of Alexandria) were collected in a vineyard in Yotala, Department of Chuquisaca in southern Bolivia. In this planting of more than 1,000 plants, more than 75% were exhibiting cane dieback symptoms and many were dead or dying. No disease was observed on grape berries. Symptoms of the disease were similar to those reported for Diplodia cane dieback (1). Cankers ranging from 2 to 10 cm long and 0.5 to 3 cm wide were observed. When diseased canes were placed in a moist chamber, conidia oozed from pycnidia in black cirri. Immature conidia were hyaline and one-celled, but mature conidia were dark brown (20 to 30 × 10 to 15 μm) with one median septum and longitudinal striations. The pathogen was tentatively identified as Lasiodiplodia theobromae (Pat.) Griffon & Maubl. (synonyms Diplodia natalensis Pole-Evans and Botryodiplodia theobromae Pat.), teleomorph Botryosphaeria rhodina (Cooke) Arx) (2). Fungi were isolated from cankers on diseased canes by surface disinfestation in 0.25% NaOCl for 5 min and placing small pieces of tissue on 2% water agar or potato dextrose agar (PDA). L. theobromae was isolated from these tissues. Koch's postulates were fulfilled by inoculating grape berries and canes with the pathogen. Five grape berries were surface disinfested and inoculated by wounding with a sterile scalpel and inserting a piece of fungal mycelium on PDA in the wounded sites. The same number of control berries was similarly treated with sterile PDA. Inoculated and control berries were placed in plastic, moist chambers in the laboratory at ambient temperature (15 to 28°C) in the dark. Five canes on two potted plants were inoculated with the same isolate of the pathogen in a similar manner as the berries. The inoculated and control sites on canes were wrapped with masking tape. Plants were placed in a moist chamber for 5 days. After 8 days, inoculated berries were rotting and the inoculated sites were covered with grayish mycelium. Within 12 days, cankers as much as 3 cm long developed on the inoculated canes, and in some lesions, black pycnidia were observed. No lesions developed in the wounded control canes. The pathogen was reisolated from inoculated berries and canes, but not from control berries or canes. The teleomorph was not observed on any naturally infected canes or on those inoculated with the anamorph. The pathogen was identified as L. theobromae based on symptoms (1), cultural and morphological characteristics (2), and pathogenicity tests. The disease poses a potential threat to the cultivation of grapevine in southern Bolivia. To our knowledge, this is the first report of Diplodia cane dieback of grapevine in Bolivia.

Defeating Cane Diseases: Plant Pathologists and the Development of Disease Control Strategies in the Australian Sugar Industry, 1920 - 1950

Between 1920 and 1950, the Queensland sugar industry was troubled by many of the diseases that plagued sugar cane, often in serious proportions. Financial losses from these disease outbreaks in the 1920s prompted the Colonial Sugar Refining Company (CSR) and the Queensland Bureau of Sugar Experiment Stations (BSES) to employ university-trained plant pathologists who undertook research into identifying the diseases, understanding their etiology and devising control strategies to reduce their impact. Archival records, annual reports of both organizations and published scientific papers are used to reconstruct the programmes of research undertaken into these diseases. Control strategies developed as a result of this research included restrictions on the movement of cane plants, the establishment of quarantine districts, use of disease-free planting material, pre-treatment of planting material with hot water and/or solutions of organic mercurial fungicides, and 'roguing' of diseased cane plants. Consequently, by 1950, gumming, Fiji and downy mildew diseases — three of the most troublesome cane diseases in Australia — had been virtually eliminated in sugar-producing districts.

Molecular Assessment of Diversity among Pathotypes of Colletotrichum falcatum Prevalent in Sub-Tropical Indian Sugarcane

Six pathotypes of Colletotrichum falcatum, responsible for Red-rot in sugarcane, prevalent in subtropical India were examined for genetic relationships using RAPD markers. A high degree of polymorphism (78.6%) was observed using 40 RAPD markers. More than 50% genetic divergence was found among the pathotypes and UPGMA cluster analysis of genetic similarity indices grouped the six pathotypes into two clusters. Cluster I comprised pathotypes Cf01 and Cf09, while cluster II comprised the remaining four pathotypes. Cf02 and Cf08 were the most closely related among all the pathotypes. Pathotype-specific unique bands generated in RAPD profiling are being used for developing markers for pathotype identification in diseased cane samples.

Induction of systemic resistance by plant growth promoting rhizobacteria against red rot disease in sugarcane

Plant growth promoting rhizobacteria (PGPR) belonging to fluorescent pseudomonads group were isolated from sugarcane rhizosphere. Selected strains were studied for the induced systemic resistance (ISR) againstColletotrichum falcatum Went causing red rot disease in the sugarcane stalks by three different resistance evaluation methods. The talc based formulations of the PGPR strains were prepared and applied through different methods and in different growth phases of the crop in the field. The pathogen was inoculated artificially later in the upper internodes and ISR was assessed. All the tested PGPR strains have significantly reduced the disease development in the stalks. ISR effect was more pronounced when the resistance was evaluated by nodal method of testing. In another trial the PGPR strains were applied to the basal stalk region in the marcotting mixture. When the pathogen was inoculated later on the upper internodes, disease development was significantly reduced in the PGPR treated canes as compared to the untreated controls. The induced resistance was maintained upto 90 days in the host after the PGPR treatment. In all these studies disease development was contained in a highly susceptible sugarcane cultivar CoC 671. When the pathogen load in the diseased canes was assessed by ELISA it was found that the PGPR treated canes recorded low titer than the control treatments. Biochemical studies indicated enhanced levels in the defense related enzymes like chitinase and peroxidase in the treated cane tissues. The pathogen inoculation resulted in lower brix, purity and commercial cane sugar percent in the PGPR untreated canes compared to the PGPR treated ones. Moreover acid and neutral invertase levels were significantly higher in the former than the latter. The induced resistance in sugarcane especially in a highly susceptible variety offers a possible alternative approach to tackle the disease under field situations and to enhance sugarcane yield.

Transmission of the Pineapple Disease Organism of Sugarcane by Nitidulid Beetles in Hawaii12

Urophorus humeralis (F.), Carpophilus hemipterus (L.), and Haptoncus ocularis (Fairmaire) were proven to be important vectors of pineapple disease of sugarcane, Ceratocystis paradoxa (Dade) Moreau in Hawaii. Viable spores were carried on the body surface but not in the feces of U. humeralis. Once it acquired the pathogen, individuals of U. humeralis could make a maximum of 13 transmissions (2-min inoculation period) and remain infective up to 12 days. Nitidulids were attracted to diseased cane, which also proved to be a better food source for both adult and young U. humeralis than healthy sugarcane stalks.

Sugarcane smut ( Ustilago scitaminea) in Kenya : I. Epidemiology

The terminal smut whip, produced by modified activity of the apical meristems of diseased canes, releases inoculum over a period of about 3 months. The maximum rate of release (c 8 × 106 spores/day) occurs in the middle of this period. Although some deposition occurs on various cane surfaces including lateral buds, infection in the field is chiefly restricted to young tiller buds as they emerge through the soil. Irrigation substantially increases the severity of disease; the presence of liquid water appears to be necessary for spore germination. Fresh sugarcane debris and washings from sugarcane leaves increase spore germination at the surface of soils. Considerable germ-tube elongation occurs on cane surfaces and multiplication of inoculum through the production of secondary sporidia can occur on mature leaves and cut surfaces. The period from infection to whip production is about 6 months under field conditions. Although multiplication of inoculum occurs during the life of the crop, a decreasing tillering rate causes the crop to become more resistant so that epidemic increase tends to be linear. It is considered that removal of diseased plants early in the crop cycle and the protection of young ratoon crops from infection are most important in checking the initial stages of an epidemic. The disease is particularly favoured under conditions of surface irrigation in hot areas.

Título en español.

La enfermedad de la raya clorótica de la yerba Merker (Pennisetum purpureum Schumac) tiene muchos rasgos en común con la raya clorótica de la caña de azúcar. Los síntomas que presentan las hojas son similares. Ambas enfermedades pueden ir en la semilla y también ambas pueden evitarse si se sumerjen las semillas afectadas en agua caliente (52°C.) por 20 minutos. La yerba enferma con la raya clorótica se encontró, corrientemente, cerca de caña enferma con raya clorótica, o pudo localizarse el sitio de donde provenía la enfermedad que era también donde la caña estaba enferma. La infección en ambas cañas (1, 6) y en la yerba causó grandes pérdidas en el tonelaje. Algunos experimentos con caña de azúcar (1, 6) revelaron pérdidas en sacarosa y en tonelaje. En este trabajo con yerba Merker se encontró que la enfermedad de la raya clorótica retardó la madurez. Posiblemente, la enfermedad de la raya clorótica en la caña de azúcar trastorna su madurez normal bajo ciertas condiciones y de esta manera disminuye los rendimientos de azúcar. No sería hasta que se hagan estudios de transmisión para determinar la posible relación entre las enfermedades de la raya clorótica que atacan la caña y la yerba Merker, que la evidencia de su semejanza podría garantizar firmemente el poder seguir suponiendo que ambas son causadas por el mismo virus. El control de ambas enfermedades, tanto en la caña de azúcar como en la yerba Merker, deben propulsarse a la vez como medida de seguridad.

A MOSAIC VIRUS OF GRASSES, NOT VIRULENT TO SUGAR CANE

Summary.This paper records studies of a mosaic disease observed in maize and Sorghum spp. in the Transvaal, South Africa. In these hosts the signs produced were not distinguishable from those produced by the common sugar cane mosaic virus. Leaf‐cage experiments showed that Aphis maidis Fitch was capable of transmitting the virus to maize.In the part of the Transvaal where the mosaic was found all sugar cane seen was free from mosaic. Sugar cane failed to contract the disease, both in a field experiment extending over three years in the Transvaal and in large cage experiments in Natal. The method employed in the Natal experiments was always successful in transmitting mosaic to sugar cane when the source of infection was either diseased cane or diseased grasses collected in the neighbourhood of diseased cane.It is concluded that the Transvaal virus is not virulent to sugar cane and is therefore different from the common sugar cane mosaic virus.

THE EFFECT OF MOSAIC ON THE CONTENT OF THE PLANT CELL

1. The mosaic pattern is indistinct on the very young leaves; becomes prominent with the growth of the leaves; then becomes less distinct with age. 2. The chlorotic areas tend to become green with age. This is probably due to the action of the sunlight on the chloroplasts. 3. The chloroplasts in the chlorotic areas are fewer in number and smaller than in the green areas. There is no evidence of disintegration. 4. The tendency of the chlorotic areas to become green with age is due to increase in number and size of the chloroplasts. 5. The chlorotic areas can be detected by cytological studies before the unfolding of the leaves. 6. The chlorotic areas increase in size by cell division and cell growth and not by the infection of surrounding cells or by a disintegration of the chloroplasts of the surrounding cells. 7. The formation of apparently new chlorotic areas in leaves is probably due to very small infected areas which increase in size with the general growth of the cells. 8. Green areas in a chlorotic area can be detected by cytological studies before they can be detected by the unaided eye. 9. The small size and number of chloroplasts is common to both sugar cane and tobacco when infected with mosaic. 10. The nuclei of diseased cane cells are usually enlarged or deformed, but this is not true of tobacco.