Early detection of onion neck rot disease in Manitoba

Neck rot caused by the fungus Botrytis allii Munn. is one of the most devastating diseases of onions (Allium cepa L.) resulting in significant yield losses. This disease is latent in nature developing symptomless onion plants in the field with bulbs typically showing symptoms 1-2 months after harvest in the storage. Molecular studies were conducted to detect latent infections of Botrytis neck rot in the onion fields of Manitoba, Canada. Plant samples of onion cultivars Redwing and Pocono were collected every 10 days throughout the growing season starting from planting until bulb harvesting during 2018, 2019, and 2020 from a research farm in Brandon, Manitoba, and plant samples of cultivar Redwing were collected during 2019 and 2020 from a commercial vegetable farm in Portage La Prairie, Manitoba. The amplified DNA fragment of onion leaves and neck region of collected samples were subjected to polymerase chain reaction (PCR) using Botrytis specific primer pair BA2f/BA1r. Botrytis allii was detected on onion samples collected from the commercial farm as early as the end of June 2019 and 2020 when plants were at the 5-7 leaf stage. The majority of onion samples collected from the research farm also started testing positive for the pathogen from June (2019, 2020) and July (2018) onwards. This knowledge about the timing of infection in the field will be useful in helping farmers to develop and evaluate management strategies in the field, and also predict the storability and availability of quality bulbs for sale.

Ciborinia allii (neck rot of onion).

C. allii is associated with the same serious neck-rot disease of onion as Botrytis allii. In general, B. allii is considered to be the more important of the two (Presly, 1985; Stewart and Franicevic, 1994; Lacy and Lorbeer, 1995). Losses of up to 50% have been reported due to neck rot of onions in storage (Kritzman and Netzer, 1978).

HARMFULNESS OF MYCOSISS ON CULTURE OF GARLIC WINTER-ANNUAL IN THE CONDITIONS OF MOSCOW REGION

One of stressful factors the reducing harvest and quality of bulbs of garlic winter (Allium sativum L.) defeat is diseases of various etiology. Studying of influence of factors of the external environment and stability of a genotype on prevalence of diseases on landings of garlic winter and degree of their injuriousness in the conditions of the Moscow region was the purpose of researches; assessment of collection and selection samples of garlic winter and identification among them steady against the most economically significant diseases. Object of researches were grades and collection samples of garlic of the Federal Scientific Vegetable Center, winter from collections, and other selection institutions. Field experiments and assessment were carried out on a natural infectious background for a number of years. It is as a result established that in the conditions of the Moscow region during vegetation of a plant of garlic winter mainly are surprised mushroom diseases (mycoses) among which the dominating position is taken by fusariosis (micromycetes of the sort Fusarium spp). Defeat of garlic fusariosis is shown annually and with different intensity, depending on weather conditions. The analysis of literature and results of our researches show that number and a ratio of types of Fusarium spp. in a pathogenic complex changes in last years. The types which are earlier not noted on the culture of garlic in the Moscow region (since 2009 – F. avenacium, F. proliferatum, F. subglutinans and F. semitectum are registered; since 2017 – F. gibbosum and F. nivale). In a complex with highly aggressive types of F. solani and F. oxysporum they enhance injuriousness of fuzariosis withering and rots. Mushrooms of the sort Alternaria and other micromycetes of the sorts Stemfillium, Pythium, Embilisia, Verticillum, Cladosporium in the conditions of the Moscow region meet mainly in a complex Fusarium. Gray rot (the activator – Botrytis allii L.) it is more often shown in storage time and transportations of bulbs of garlic. These micromycetes enhance injuriousness of fusariosis and increase losses of a harvest of garlic winter, especially, in the conditions of sharp fluctuations of average daily temperatures and humidity of the soil during the different periods of vegetation. Results of long-term assessment are given in article, grades and perspective collection samples of garlic winter the steadiest against defeat with diseases in the conditions of the changing climate of a zone of Non-Black Earth Region are allocated.

Effect of Postharvest Chemical Treatments, Heat Curing, and Refrigerated Storage on Marketability of Short-day Onions

Vidalia onions (Allium cepa) are very susceptible to infection from pathogens and diseases compared with other types of onions. Botrytis neck rot (BNR) (Botrytis allii) is the most common and destructive storage disease, whereas sour skin (Pseudomonas cepacia) can cause significant bacterial losses, particularly, for late season cultivars. The objective of this study was to assess the effects of different fungicide and bactericide drenches on marketability of Vidalia onions using the cultivar Savannah Sweet grown, harvested, and graded for high-quality onions. Six different fungicide treatments were evaluated, including fludioxonil at two different rates, fluopyram and pyrimethanil in combination, and pyraclostrobin and boscalid in combination with a water-only and an untreated entry. In addition, four different bactericide treatments were evaluated, including copper hydroxide and copper sulfate pentahydrate with a water-only and untreated control. Treatments were applied by drenching the onion bags with 1 gal of solution at the desired concentration. Onions treated with fungicide were inoculated with the pathogen that causes BNR, whereas the bactericide treatments were inoculated with the pathogen that causes sour skin by placing a single inoculated bulb into each bag. Half of the bags were heat-cured for 48 hours and all of the onions were stored immediately under refrigerated conditions at 34 to 36 °F for 2 or 4 months. Bactericide treatments were not heat-cured the second year of the study. Onions were evaluated after 1 and 14 days of shelf life. For both years, all the fungicide applications were effective with more marketable onions compared with the controls. Fludioxonil, fluopyram/pyrimethanil, and boscalid/pyraclostrobin had the highest percentage of marketable onions compared with the water or untreated controls. Fluopyram/pyrimethanil and boscalid/pyraclostrobin fungicides had significantly higher percentage of marketable onions than the controls but were similar to the low rate of fludioxonil. Bactericide applications were not effective in reducing losses when compared with the controls.

Fungal diseases of Rose plant in Bangladesh

Five types of symptom were recorded on two varieties of rose plant. The symptoms were Black spot, Leaf spot1, Leaf spot2, Blight and Anthracnose. The study revealed the presence of 20 species of fungi belonging to 17 genera. The isolated fungi were Alternaria alternata (Fr.) Keissler, Arthrinium saccharicola Stevenson, Aspergillus flavus, Link., A. niger van Tiegh., Botrytis allii Munn, Cercospora sp., Cladosporium cladosporioides (Fresen.) de Vries, C. oxysporum Berk. & Curt., two species of Colletotrichum, Curvularia brakyospora Boedijn, Curvularia pallescens Boedijn, Fusarium sp., Epicoccum purpurascens Ehreneb ex Schlecht; Link, Gibberella sp., Marssonina rosea (Lib.) Died, Nigrospora sphaerica (Sacc.) Masson, Pestalotiopsis guepinii (Desm.) Stay. with its two culture types, Penicillium sp., Rhizopus stolonifer (Ehrenb. Ex. Fr) Vuill. and Trichoderma viride Pers. ex Fries. The frequency (%) of association of P. guepinii was higher than any other fungi. Pestalotiopsis guepinii and its two culture types were found to be pathogenic to rose plant. DOI: http://dx.doi.org/10.3329/jbas.v38i2.21347 Journal of Bangladesh Academy of Sciences, Vol. 38, No. 2, 225-233, 2014