Tuber Rot Research Articles

The effects of calcium fertilizer on anthracnose and Rhizopus tuber rot of yam

Yam (Dioscorea spp) production is beset in the field and in storage by major fungal pathogens, namely Colletotrichum gloeosporioides that causes anthracnose in the field, and Rhizopus stolonifer that causes tuber rot in storage. Alternative control measures are imperative as conventional control of these pathogens is either ineffective or detrimental. This study investigated the effects of calcium fertilizer on the incidence and severity of anthracnose and Rhizopus rot of yam. Calcium nitrate fertilizer was applied to soils naturally infected with C. gloeosporioides, at the rates of 0, 3, and 4kg ha-1. D. rotundata variety Efuru was planted. The treatments were arranged in a randomized complete block design with three replicates. Anthracnose disease rating relied on natural endemic infection in the field, while inoculation of harvested yam tubers was carried out using R. stolonifer. There was no significant effect of calcium amendment of the soil on anthracnose severity in D. rotundata or on the agronomic parameters. D. rotundata tubers treated with 3 and 4kg ha-1 calcium soil amendments had reduced infection by R. stolonifer in storage compared to the control treatments. The study concluded that calcium applied to the soil had reduced storage losses by R. stolonifer in D. rotundata but had no influence on anthracnose severity in the field. Therefore, 3kg ha-1 of calcium nitrate applied to the soil can be used to improve D. rotundata tuber resistance to R. stolonifer, and is recommended for high-quality tuber storage.

Field asymmetric ion mobility spectrometry for pre-symptomatic rot detection in stored Ranger Russet and Russet Burbank potatoes

This study was aimed at early detection and rot progression monitoring in stored potatoes using a portable field asymmetric ion mobility spectrometry (FAIMS) system. Tuber samples of Ranger Russet (RR) and Russet Burbank (RB) cultivars were inoculated with Pectobacterium carotovorumsubsp.carotovorum (causes soft rot) and sterile water (control). The samples were stored in jars either at room temperature (25 °C with 30 % relative humidity [RH]) or reduced temperature (4 °C with 95 % RH). Volatile headspace from samples was scanned with FAIMS at regular intervals up to 14 days for room temperature and 31 days for reduced temperature storages. Infection symptoms were detected for higher ion current pertinent to headspace of inoculated samples compared to the controls of both the cultivars. Such discrimination was evident at FAIMS compensation voltage (CV)-dispersion field (DF) ranges of −1.70–1.31 V and 38–90 % for room temperature and −1.58–1.31 V and 36–92 % for reduced temperature storages. The rot was detected as early as one day after inoculation (DAI) under room temperature and five DAI under reduced temperature storages. The ion currents were affected by the storage temperature and humidity, and associated interaction with the DAI and cultivar (F7,712 = 21.6–31.4, p < 0.001). The FAIMS responses of control and inoculated tubers were also classified by the Naïve Bayes and Random Forest algorithms at accuracies in the ranges of 70–90 % and 75–100 %, respectively. Overall, a portable and tunable FAIMS system was found suitable for high throughput early detection of soft rot in potato tubers. Future studies need to revalidate the FAIMS system in commercial storage facilities for timely rot detection and initiation of potential remedial measures.

Impact of Fusarium dry rot on physicochemical attributes of potato tubers during postharvest storage

Fusarium is a major spoilage fungus of potato tubers during post-harvest storage. The dry rot disease caused by Fusarium species severely affects the harvested potatoes and impose a critical loss to processing industries and consumers. In our experiment, we investigated the occurrence of Fusarium sambucinum (FS) and Fusarium oxysporum (FO) as major storage fungus causing Fusarium dry rot in potato tubers. Further, we performed morpho-molecular identification of both the fungi and confirmed their pathogenicity on potato tuber during storage. We evaluated the susceptibility parameters and quality attributes during infection in two popular cultivars namely ‘Kufri Pukhraj’ (table purpose) and ‘Kufri Chipsona 3’ (processing purpose). Out of two cultivars, ‘Kufri Pukhraj’ was shown to have greater susceptibility as compared to ‘Kufri Chipsona 3’ in terms of lesion diameter, fungus penetration and rot volume during periodic observation of 20, 40 and 60 d of storage. FS was highly aggressive as compared to FO. However, a mixed inoculum of Fusarium species caused higher damage irrespective of cultivars. The physicochemical analysis revealed that fungus infection (individual or mixed inoculum) leads to a reduction in starch and amylose content in both the cultivars after 60 d of storage. Moreover, amylopectin, reducing sugars, sucrose and total soluble sugar content were increased in response to fungal infection in both cultivars. Pearson correlation analysis indicated that lesion diameter and rot volume was negatively correlated (R < -0.80) with starch and amylose content. However, amylopectin, reducing sugar, sucrose and total soluble sugar was positively correlated with susceptibility parameters. This study highlights the impact of storage fungus infection on the nutritional quality parameters of potato tubers which is a critical concern for consumers and processing industries.

The effect of tillage depth and micro-fertilizer addition on the growth and production of cassava (Manihot esculenta Crantz) planted in early dry season

The climate change from the dry season to the rainy season, causes cassava to rot a lot when harvested, this research was conducted in the early dry season by practicing two tillage depths to handle the excessive water around the rooting area, and by addition of micro-fertilizer. This study aimed to determine the cassava growth and yield when planted at the early dry season, combined with tillage depth and micro-fertilizer addition. This research was conducted in South Lampung Regency, Lampung Province, Indonesia. The cutting stems of cassava were planted in the early dry season (May) and harvested in April 2020. The tillage depth consisted of two depths: shallow tillage, above hardpan layer (30 cm), and deep tillage, including hardpan layer (60 cm). Micro-fertilizers were applied with two dosages: without fertilizer (0 kg ha−1) and with fertilizer (40 kg ha−1). Those treatments were arranged factorially (2x2) in Strip Plot Design with three replications. The result showed that deep tillage caused the rotten tubers only 15 tubers compared with the shallow tillage which was 39 tubers. The treatment of micro-fertilizer (40 kg ha−1) on the contrary increased the rotten tubers up to 35 tubers. In general, deep tillage could increase the dry weight of tubers, and micro-fertilizers could increase the fresh weight of tubers.

Calcium Nitrate Fertilization Effect on Anthracnose Caused by Colletotrichum Gloeosporioides Penz., Tuber Rot By Rhizopus Stolonifer Ehrenb. and Yield in Dioscorea Alata Variety Atoroku After Fallow

Calcium nitrate soil amendment fertilization effects on anthracnose disease caused by Collettrichum gloeosporioides, tuber rot by Rhizopus stolonifer and yield were determined in Dioscorea alata variety Atoroku (a local variety from South West Nigeria). The field design was RCBD (randomized complete block design) with 3 treatments and 3 replicates. The 3 treatments were calcium at 0, 2 and 4 kg ha–1 from calcium nitrate (analar grade) applied at 3 MAP (months after planting). N in the experimental site was below the critical determined for optimum yam production in South West Nigeria, but Ca, Mg and K were above the critical. At 4 MAP, shoot number (mean, 3.68) was comparable/similar across treatments, but shoot length (3.43 m) was higher in the 2 kg ha–1 treatment than others. At 5 MAP the control and 2 kg ha–1 calcium fertilized plants had higher shoot number, a mean of 5, than the 4 kg ha–1 calcium fertilized plants, whereas shoot length had become similar in the treatments. Tubers were inoculated and incubated for two weeks with Rhizopus stolonifer, an economic yam storage pathogen in Nigeria, after the 5MAP and 6MAP harvests. There were no significant differences in weight loss or infection in the incubated tubers at 5MAP. Weight loss of 11.01% in the 2 kg ha_1 incubated calcium-fertilized tubers were significantly higher than in the control (3.20%) and the 4 kg ha_1 treatment (1.90%) at 6MAP. However infection was significantly lower in the 2 kg ha_1 (0.78%) and 4 kg ha_1 (0.86%) calcium-fertilized tubers than the control (2.25%) at 6MAP. Calcium nitrate at 2 kg ha_1 and 4 kg ha_1 soil amendment may be used in smallholder farmers plots to reduce infection in D. alata variety Atoroku tubers if the six months after planting is desired for income as is the practice for white guinea yam 6MAP milk harvest in Nigeria. Anthracnose severity scored at 8MAP was moderately susceptible in the 4 kg ha_1 treatment (3.17), control (2.83) and the 2 kg ha_1 treatment (2.75) and were not significantly different from one another. Reduction of anthracnose may be further determined with one or two foliar sprays in addition to the 3MAP calcium nitrate soil amendment, as well as leaf calcium analysis to ascertain the optimum concentration commensurate to anthracnose resistance. Shoot number per plant at 8MAP was in the range 2.07 to 2.54 with no significant differences among the three treatments. Tuber number per plant was also not significantly different and was 3.55, 4.27 and 3.18 in the 0, 2 and 4 kg ha_1 treatments. Plant weight above the mound of 4.78 kg and tuber weight of 5.35 kg in the 4 kg ha_1 treatment at 8MAP harvest was significantly higher than the control (3.25 kg and 3.55 kg respectively), and the 2 kg ha_1 treatment (3.05 kg and 3.25 kg respectively), whereas both were similar in the control and the 2 kg ha_1 treatment. The 8MAP yield of 3.55 kg, 3.25 kg and 5.35 kg in the 0, 2 and 4 kg ha_1&nbsp; treatment is the equivalent of 35.5, tons ha_1, 32.5 tons ha_1 and 53.5 tons ha_1 and are higher than the expected 15 to 25 tons ha_1 with 400 kg (8 bags) NPK 15-15-15 (ICS-Nigeria) and also in the range of the estimated potential of 30 to 75 tons ha_1 (Zinsou, 1997; Diby et al., 2004). Calcium nitrate soil amendment at 4 kg ha_1 is recommended for increase in yield in Dioscorea alata variety Atoroku after fallow in South West Nigeria or areas of similar soils.

Parasitic nematodes in potatoes of different varieties and their interrelations with some arthropods

Introduction. Potato (Solanum tuberosum L.) is susceptible to infestation with an associated complex of different species of parasitic and saprophytic nematodes, bacteria, fungi, and arthropods, which diminish the quality of the product. Material and methods. 10 varieties of potatoes were investigated (Agata, Albastriu-mov, Bella rosa, Concorde, Desiree, Irga, Iagodca, Roko, Romano, Sprinter), cultivated on the territory of the Republic of Moldova. The extraction of nematodes and mites was performed using the Baermann funnels, modified by Nesterov.Results. Multiannual researches on the degree of potato infestation have shown that tubers are preferred by various arthropods (Acaridae), Agriothes spp. (Elateridae), Gryllotalpa gryllotalpa, (Grillotalpidae) and Sciaridae spp . (Sciaridae), which form different interactions with the parasitic nematodes of tubers (Ditylenchus destructor, D. dipsaci).Conclusions. Solanum tuberosum infested by parasitic nematodes D. destructor in association with saprophytic nematodes and dry rot are colonized by nematophag ous (mites – 80%) and phytophagous arthropods (wireworms – 40%; mole cricket – 50%; flies – 40%). Among the researched arthropods, Rhizoglyphus echinopus were more frequently found, which together with other species actively consume the primary and secondary parasitic nematodes, their mortality constituting up to 90%. In the traumatized by some arthropods potatoes, with the soil, secondary parasitic nematodes, also penetrate, carrying bacterial and fungal infections, subsequently stimulating the total rot of potato tubers.

QTLs for potato tuber resistance to Dickeya solani are located on chromosomes II and IV

AbstractThe goal of this research was to identify quantitative trait loci (QTLs) for potato tuber resistance to the soil‐ and seedborne bacterium Dickeya solani and for tuber starch content, to study the relationship between these traits. A resistant diploid hybrid of potato, DG 00‐270, was crossed with a susceptible hybrid, DG 08‐305, to generate the F1 mapping population. Tubers that were wound‐inoculated with bacteria were evaluated for disease severity, expressed as the mean weight of rotted tubers, and disease incidence, measured as the proportion of rotten tubers. Diversity array technology (DArTseq) was used for genetic map construction and QTL analysis. The most prominent QTLs for disease severity and incidence were identified in overlapping regions on potato chromosome IV and explained 22.4% and 22.9% of the phenotypic variance, respectively. The second QTL for disease severity was mapped to chromosome II and explained 16.5% of the variance. QTLs for starch content were detected on chromosomes III, V, VI, VII, VIII, IX, XI, and XII in regions different from the QTLs for soft rot resistance. Two strong and reproducible QTLs for resistance to D. solani on potato chromosomes IV and II might be useful for further study of candidate genes and marker development in potato breeding programmes. The relationship between tuber resistance to bacteria and the starch content in potato tubers was not confirmed by QTL mapping, which makes the selection of genotypes highly resistant to soft rot with a desirable starch content feasible.

Penggunaan Trichoderma Sp. Untuk Mengendalikan Busuk Umbi Pada Bawang Merah (Allium Ascolanicum L.)

The research objective was to determine the use of Trichoderma sp. to control shallots tuber (Allium ascalonicum L.). The research was conducted at Growth Center, Jl. Peradilan Tata Usaha Negara No. 1 Kenangan Baru, Percut Sei Tuan District, Deli Serdang Regency, 25 meters above sea level (asl). The design used was a factorial randomized block design (RBD) consisting of 2 factors, namely the factors of administration of Trichoderma sp. Consists of 5 levels, namely: T0: Control (without Trichoderma sp.), T1: 10 g Trichoderma sp./polybag, T2: 20 g Trichoderma sp./polybag, T3: 30 g Trichoderma sp./polybag, T4: 40 g Trichoderma sp./polybag. and time of giving Trichoderma sp. Consists 2 levels, namely: W1: Trichoderma sp. given 1 week before planting, and W2: 1 week after planting with 10 treatments combination. Observations included plant height (cm), number of leaves per clump (strands), number of tillers per clump (tuber), tuber wet weight per sample (g), tuber dry weight per sample (g), and the percentage of tuber rot attack. The results showed that: 1). The use of Trichoderma sp. with various doses (T0, T1, T2, T3, and T4) significant effect on plant height but no effect on observed other. While application time of Trichoderma sp. 1 week after planting (W2) showed a significant effect on plant height, number of leaves, number of tillers. also significantly affected wet weight, dry weight, and the percentage of tuber rot attack. 2). The combination of the two treatment factors had no significant effect on all observed parameters.

Occurrence of Postharvest Fungal Rots of Sweet Potato (Ipomoea batatas (L) Lam.) in Southwest Nigeria and their Control with Sawdust Extracts

A study was conducted in three agroecological zones (AEZs) of Southwest, Nigeria to evaluate the incidence and pathogenicity of postharvest fungal rots of sweetpotato and their control with extracts of sawdust from some tropical trees. Survey of rotted tubers was conducted in 18 markets across the three AEZs: humid rainforest (HF), derived savannah (DS), and southern guinea savannah (SGS). Fungi associated with rotted tubers were isolated, identified and their pathogenicity determined. In vitro fungitoxicity of Anogeissus leiocarpus, Gmelina arborea and Cola nitida sawdust extracts were assessed in an experiment laid out in a Completely Randomized Design (CRD) with 3 replicates. Six fungi species found to be associated with rot on tubers were Botryodiplodia theobromae, Rhizopus stolonifer, Aspergillus niger, Trichoderma viride, Penicillium oxalicum and Fusarium oxysporum. Highest (35%) rot incidence was observed in HF zone with R. stolonifer as the most prevalent. Botryodiplodia theobromae was most prevalent (68.75%, 54.54%) in SGS and DS zones respectively. All the six isolated fungi were pathogenic to sweetpotato but induced varying levels of rot severity. Botryodiplodia theobromae, R. stolonifer or A. niger induced complete (100%) rot of inoculated tubers. Sawdust extracts reduced mycelial growth of test pathogens at three sawdust concentrations (50 g/L, 75 g/L and 100 g/L) tested. Inhibition of fungal growth increased with extract concentration. Anogeissus leiocarpus sawdust extract at 100 g/L exhibited highest range of mycelial growth inhibition (8.80 - 73.0%) across tested pathogens. Gmelina arborea sawdust extract at 100 g/L significantly inhibited (p&lt;0.05) mycelial growth of B. theobromae, P. oxalicum and T. viride while C. nitida exhibited strong fungitoxicity to F. oxysporum at 100 g/L. Application of the sawdust extracts at 50 g/L, 75 g/L and 100 g/L concentrations has the potential to minimize postharvest fungal rot of sweetpotato.

Quantification of Pathogenicity Genes Expression in Pectobacterium carotovorum by qRT-PCR

Bacterial soft rot disease is one of the most important and widespread bacterial diseases that cause destructive losses to the crop in a matter of days. The disease causes severe many vegetable crops including potato. In this study, four isolates of Pectobacterium carotovorum the main causal of the soft rot disease were isolated from naturally rotted tubers. Then, the isolates were subjected to a new set of primer pairs designed to amplify the pel gene which distinguish the P. carotovorum strains. The results confirmed that four isolates belong to P. carotovorum by having the pel gene. Then, a pathogenicity test was performed on potato tubers which showed variability between the isolates in pathogenicity and diseases severity. Finally, a quantitative reverse transcriptase PCR (qRT-PCR) techniquewas used to investigate the effect of the presence of the potatoes tissues on stimulating the expression of the pathogenicity genes. The gene expression of five pathogenicity genes was studied included: polygalacturonase (Peh), pectate lyase (Pel), xylanase (Xy), protease (Prt), and cellulase (Cel). The results confirmed that the presence of potatoes tissues stimulates the expression of pathogenicity genes in both strong and weak P. carotovorum isolates.

Fusarium oxysporum strains from wilting potato plants : Potential causal agents of dry rot disease in potato tubers

The present study focused on the isolation, identification and assessment of the dry rot-causing ability of Fusarium spp. associated with potato wilt in the Middle Volga region of Russia. A total of 14 Fusaria were isolated from the root necks of wilting potato plants. One isolate was identified as Fusarium solani, while the remaining thirteen of the isolates related to the species Fusarium oxysporum. Artificial inoculation of potato tubers with fungal spores showed that tubers of the cultivar Reggi exhibited the highest resistance [cultivar resistance index (CRI) = 0.78] to the tested isolates, while susceptibility (CRI = -0.44) was registered in tubers of the Zhukovskij rannij cultivar. The manifestation of dry rot during artificial inoculation with the spores of vascular-associated Fusaria was significantly influenced by pathogen virulence [H (9, N = 300) = 60.630, p <0.000001] and plant cultivar type [H (2, N = 210) = 17.201, p =0.00018]. However, not all isolates inhabiting occluded vessels caused dry rot in tubers.

Suppression of Fusarium dry rot of potato using beneficial bacterial treatments

Fusarium dry rot affects up to 60% of potato tubers during storage. Pathogen resistance development to synthetic chemical fungicides is a main contributing factor. Previous work has demonstrated the use of bacterial antagonists against plant pathogens. In this study, bacteria isolated from disease suppressive composts were tested to evaluate their antagonistic activity against F. sambucinum in vitro, as well as to assess their ability to reduce Fusarium dry rot of potato tubers. To identify the potential implication of antifungal compounds in their inhibitory activity, bacterial extracts were produced and assayed against F. sambucinum mycelial growth and conidial germination. In vitro results showed that all tested bacteria suppressed F. sambucinum mycelial growth over six days of incubation. When testing the bacteria against potato dry rot, 30 of 32 bacteria reduced the symptoms of the disease at the higher bacterial concentration tested. The combined in vitro and in vivo studies indicated Bacillus subtilis B9–8, Pseudomonas moraviensis F9–6, Pseudomonas koreensis F9–9, and Pseudomonas gessardii M9–16 were the most effective strains. Extracts from these four bacteria were able to inhibit mycelial growth and/or conidial germination of the fungal mold. Results from this study suggests that multiple antagonistic bacteria may be useful in controlling Fusarium dry rot on potato tubers. Extracts from the four most effective bacteria indicated that antibiosis was a main mode of action against F. sambucinum.

Possible Causes of Health Disorders in Stored Yam at Farm Gate

This study investigated and ascertained causes of health disorders in stored yam at farm gate in major yam producing communities in the Nanumba North District of Ghana. A mixed method research design was adopted for data collection through the application of Participatory Research Appraisal tools and techniques including individual interviews using questionnaires. Random sampling technique was used to select five communities and hundred respondents. Data was analyzed via descriptive statistics which generated summaries, Tables, histograms, and pie-charts using SAS software. Ages of respondents were in the range of 11 to over 60 years with illiterate majority. They were inadequate in their knowledge of agronomic, harvest, and postharvest practices and techniques including curing, chemical or botanical treatments for the yam tuber prior to storage. Fresh yam produce was kept in shallow dug trenches where temporal storage was the target but stored their dry yam produce intended for long periods in barns (most preferred) and on wooden platforms which were more sustainable with a little preponderance of the former. Causes of yam health disorders and associated problems in store were insect pests, rodents, weed pests, diseases (tuber rot), yam beetles, snakes, scorpions, and the inability of some storage structures to keep produce for a long time. Research, government, and other stakeholder institutions should partner up and make improved and certified yam sets accessible and affordable, and intensify agriculture extension services’ interventions that empower farmers the knowledge on agronomic, harvest, and postharvest practices and techniques.

Studies on impact of storage materials and methods on potato tuber moth, Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae) on potato

Potato tuber moth (PTM), Phthorimaea operculella Zeller originated in Latin America and co-evolved with its host plant potato (Solanum tuberosum L.). It has become one of the most serious insect pests around the world, including in India. Laboratory studies were conducted against PTM for the pest build-up; % tuber dried and rot and extent of tuber tunneling. The mean% infestation of PTM using different storage materials after 90 days of storage was witnessed highest (56.92%) in wooden bins and it was least in cartoon box stored tubers (48.59%), while among different storage methods, it was recorded highest with 61.88% in plastic bin stored tubers and was lowest in low temperature stored tubers (5.45%).% tubers dried after 90 days of storage period was maximum in tubers inserted with agave leaf bits (40%) and it was minimum in nylon mesh bags (5%) among different storage materials. The same was resulted with no tubers dried in both low temperature and pit stored tubers among different storage methods and it was highest in heap method with paddy straw cover (10%). A maximum of 85.00% tuber rot was recorded in tubers inserted with agave leaf bits and a minimum of 10.00% in tubers stored in wooden bins among the storage materials. Among different storage methods, percent tuber rot ranged from 10.00 to 75.00% in tubers storage in low temperature and heap method, respectively. Extent of tuber tunneling among storage materials ranged from 22.22% (40 mesh nylon bags stored tubers) to cent percent (tubers stored in wooden bins and bamboo bins). The same was witnessed with a minimum of 0.33% in low temperature storage method in polythene bags and a maximum of 73.33% in plastic bin stored tubers. Therefore, the development of control technologies and intensive monitoring is necessary in future days to come, for stable potato production as well as potato post-harvest.

Bacillus spp. mediated management of soil borne diseases in Gloriosa superba L.

Gloriosa superba crop was found to be affected by two soil borne diseases viz., stem rot/root rot/tuber rot caused by Macrophomina phaseolina and tuber rot caused by Sclerotium rolfsii. Among the seven Bacillus spp. tested against M. phaseolina revealed that B. amyloliquifaciens recorded significantly higher per cent of mycelial inhibition (53.33) followed by B. endophyticus (48.89) inhibition over control. Among the different dipping concentrations tested, dipping the tubers in talc based formulation of B. amyloliquifaciens @ 1% was found to be effective in reducing the Macrophomina incidence to 16% and Sclerotium disease incidence to 36% as compared to control (72%). Pot culture studies on the management of tuber rot revealed that dipping tubers in talc based formulation of B. amyloliquifaciens @ 1% for 20 min. + soil application of talc based formulation of B. amyloliquifaciens in FYM @ 100g/plant on 30 and 60 days after planting was found to be effective in reducing the disease incidence to 40% with dry seed yield of 45.6 g/plant as compared to control (100% and 14.6 g/plant, respectively). The same treatment was effective under field condition and recorded the lowest incidence of Sclerotium (16%) and Macrophomina (14%) with the seed yield of 420 kg/ha as compared to untreated control (60% disease incidence and seed yield of 360 kg/ha). The population of Bacillus was maximum (10x 10−8 cfu/g) in treated plot soil after harvest as compared to untreated control (3 x10−8 cfu/g).

Potential for Biological Control of Postharvest Fungal Rot of White Yam (Dioscorea rotundata Poir) Tubers in Storage with Trichoderma harzianum

Potential of Trichoderma harzianum for biological control of postharvest fungal rot of white yam (Dioscorea rotundata Poir) tubers in storage was studied. Pathogenicity test revealed the susceptibility of healthy looking yam tubers to Aspergillus niger, Botryodiplodia theobromae and Fusarium oxysporum f. sp. melonganae after fourteen days of inoculation. Treatments comprising A. niger, B. theobromae and F. oxysporum each paired with T. harzianum and were arranged in completely randomized design and stored for five months between December, 2015 and April, 2016 and December, 2016 and April, 2017. Results revealed that tubers treated with the pathogenic fungi alone caused mean percentage rot of between 6.67% (F. oxysporum) and 22.22% (A. niger) while the paired treatments produced only between 2.22% (T. harzianum X F. oxysporum) and 6.67% (T. harzianum X A. niger). In the second year of storage, mean percentage rots were between 13.33% (F. oxysporum) and 28.89% (A. niger) while in the paired treatment rots were only between 6.67% (F. oxysporum X T. harzianum) and 8.89% (A. niger X T. harzianum). Tubers treated with antagonist alone produced 0.00% and 2.22% in the first and second year respectively. Result revealed that there was a significant difference (P ≤ 0.05) in mean percentage rot between the first year and the second year except where B. theobromae was inoculated alone, A. niger and T. harzianum paired and B. theobromae and T. harzianum paired. The most antagonized fungus in paired treatment for both years was F. oxysporum f. sp. melonganae while the least antagonized was A. niger and B. theobromae. The study recommended the use of T. harzianum in the control of rot causing pathogens of yam tubers in storage as better alternative ways of reducing tuber rot compared with the use of chemical fungicides which are environmentally hazardous.

Use of cumin and lavender essential oils to control phoma exigua var. foveata on potato during storage

The antifungal activity of essential oils against Phoma exigua var foveata, was investigated by analyzing its inhibitory effect on the gangrene of potato tubers. The results showed that mycelium growth and spore germination of Phoma was suppressed by treatment with essential oils, and the inhibitory effect strongly correlated with the concentration of essential oils used in this study. The effectiveness of post-harvest treatment with essential oils was studied for induced resistance to Phoma rot in tubers of two potato varieties (Kolobok and Sante). The results showed the fungicidal effect of cumin and lavender essential oils against phomosis at concentrations of 0.1, 0.2, and 0.4, significant inhibition of mycelium growth (18.1-100%), and viability of conidia (12.8-100%) compared to the control. Moreover, both oils at a concentration of 0.4% caused 100% inhibition of mycelium growth and spore germination. Treatment with oils at a concentration of 0.01-0.04 l/t significantly reduced the degree of damage to tubers infected with phomosis. However, cumin essential oil at a concentration of 0.04 l/t had the greatest effect 97.1% compared to lavender oil 95.4%.

Utilization of Endophytes Fungi from Jatropha Leaves (Jatropha curcas L.) Against Fusarium oxysporum Causing Tuber Rot Disease Onion (Allium cepa var. Ascalonicum (L.) Backer)

Tuber rot is one of the important diseases in onion caused by Fusarium oxysporum. Endophytes are biological agents that are currently widely used in controlling plant diseases. Excessive use of pesticides and continuously has shown negative impacts such as resurgence, resistance to pests and pathogens, and the death of natural enemies. Currently, pests and pathogens control effort are directed at the utilization of natural enemies or better known as biological control. Endophyte is a microorganism that grows in plant tissues without causing symptoms. Endophytes allegedly capable of producing a variety of phytochemical compounds generated by their host. The leaves of Jatropha (Jatropha curcas L.) is one part of the plant that contains secondary metabolites.Phytochemical tests on the Jatropha show that Jatropha contains alkaloids, flavonoids, and saponins that are an antimicrobial potential of plant-pathogen control agents. This study aimed to determine the effect of some Endophytes isolates and their impact on the growth of F. oxysporum in vitro in onion.Exploration (endophyte isolation from Jatropha healthy leaves) and observation (antagonist test of Endophytes of the Jatropha leaves) method used in this study was a Completely Randomized Design (CRD) with a single factor (10 treatment) repeated three times. There were 14 endophytes isolated from Jatropha leaves with a growth ratio of 4.5 cm/2 days. The best treatment to inhibit the growth of F. oxysporum in vitro is Jc5, Jc8, Jc10.

Study of infectious diseases of ornamental plants of Asteraceae family in outdoor planting collections of the Donetsk Botanical Garden

The need for regular phytopathological monitoring of collections in the Donetsk Botanical Garden is due to the risk of invasions of new plant pathogens on introduced ornamental plants under conditions phytopathogens in the 21st century, as well as the annual replenishment of the collections with new plant species, varieties, cultivars. A phytopathological examination ornamental plants collections of Asteraceae family was carried out in 2016-2019, according to which 15 genera, 19 species and 3 cultivated hybrids of plants showed various diseases caused by plant pathogenic organisms. Microfungi (30 species) predominates among the plant pathogens; plant damage caused by viral and bacterial diseases was also observed. The most common infectious diseases in the Donetsk Botanical Garden (DBG) were caused by powdery mildew fungi (recorded on 8 plant species) and rust fungi (on 5 plant species). There were found some new plant pathogenic microfungi in DBG, which were previously not recorded in the DBG and which can be treated as alien species to the region: powdery mildews of Symphyotrichum spp. (pathogen - Golovinomyces asterum ), Coreopsis spp. ( G. spadicaeus ) and Helianthus tuberosus ( G. latisporus ), rusts of Tanacetum balsamitae ( Puccinia balsamitae ) and Symphyotrichum spp. ( Coleosporium asterum ), and smut of Gaillaridia spp. ( Entyloma gaillardianum ). Various leaf spots were regularly noted in the collections, but they did not cause significant damage of Asteraceae plants in outdoor planting conditions. The most harmful types of diseases were wilting caused by Fusarium oxysporum and Verticillium albo-atrum , and rots of rhizomes and tubers of perennials such as chrysanthemums ( Chrysanthemum × hortorum ) and dahlias ( Dahlia × cultorum ) caused by Berkeleyomyces basicola , Ilyonectria destructans , Sclerotinia sclerotiorum and opportunistic pathogens Clonostachys rosea and Stachybotrys chartarum .

Potato dry rot disease: current status, pathogenomics and management.

Potato dry rot disease caused by Fusarium species is a major threat to global potato production. The soil and seed-borne diseases influence the crop stand by inhibiting the development of potato sprouts and cause severe rots in seed tubers, table and processing purpose potatoes in cold stores. The symptoms of the dry rot include sunken and wrinkled brown to black tissue patches on tubers having less dry matter and shriveled flesh. Fungal infection accompanied by toxin development in the rotten tubers raises more concern for consumer health. The widespread dry rot causing fungal species (Fusarium graminearum) is reported to have a hemibiotrophic lifestyle. A cascade of enzymes, toxins and small secreted proteins are involved in the pathogenesis of these hemibiotrophs. With the availability of the genome sequence of the most devastating species Fusarium sambucinum, it is important to identify the potential pathogenicity factors and small secreted proteins that will help in designing management strategies. Limited resistant cultivars and the emergence of fungicide-resistant strains have made it more threatening for potato cultivation and trade. Several novel fungicide molecules (Azoxystrobin, chlorothalonil and fludioxonil), are found very effective as tuber treatment chemicals. Besides, many beneficial bioagents and safer chemicals have shown antibiosis and mycoparasitism against this pathogen. Germplasm screening for dry rot resistance is important to assist the resistance breeding program for the development of resistant cultivars. This review aims to draw attention to the symptomatology, infection process, pathogenomics, the role of toxins and management approaches for potato dry rot disease, which is very much critical in designing better management strategies.