Studies on Symptomatology, Morphological and Molecular Characterisiation of Erysiphe cichoracearum Causing Powdery Mildew of Okra

Okra (Abelmoschus esculentus (L.) Moench) is a globally important annual vegetable belongs to family malvaceae, it is most broadly distributed vegetable all over the world. Among the fungal diseases affecting okra crop, powdery mildew caused by Erysiphe cichoracearum DC. is the most important disease causing considerable yield losses. The disease was characterized by the appearance of small white powdery specks on upper surface of the lower leaves which enlarged and coalesced forming bigger patches. Later on the disease spread to the upper leaves, coalescing of the white powdery specks and enlargement in their size ultimately resulted in complete coating of white fungal mass on the leaves. The morphological studies of the pathogen in the laboratory revealed, that the mycelium is septate, ectophytic, hyaline and adjacent to the mycelium, basal septum of the conidiophores was seen. The conidiophores were erect, on which conidia were produced either singly or in short chains. The conidia were found cylindrical or barrel in shape, hyaline, non-septate and measured 75.23 µm x 40.65 µm. Molecular characterisation of the native isolate resulted in the DNA amplicon at the region 531 bp. Further, DNA sequence was obtained for ITS Rdna and was deposited in NCBI gene bank. Accession number ‘MW774352’ was obtained and it was confirmed that the causal pathogen of okra powdery mildew of Raichur region is Erysiphe cichoracearum

Screening of Okra Genotypes against Powdery Mildew under Natural Epiphytotic Conditions

Okra (Abelmoschus esculentus (L.) Moench) is a globally crucialannual vegetable belonging to family malvaceae, it is the most broadly distributed vegetable all over the world. Among the fungal diseases affecting okra crops, powdery mildew caused by Erysiphecichoracearum DC. is the most crucial disease-causing considerable yield losses. Host plant resistance is one of the most practical, economical and feasible methods of management of plant diseases. An attempt was made to identify sources of resistance which could be used in developing resistant variety to mitigate loss in farmer’s field.Fifty okra genotypes were screened for their response to powdery mildew under natural epiphytotic conditions during Rabi, 2020-21Results revealed that, out of fifty genotypes screened, none of them showed immune and resistant reactions to powdery mildew. However, one genotype i.e., EC329404 showed a moderately resistance reaction. Twenty genotypes showed a moderately susceptible reaction. While twenty-two genotypes showed susceptible reaction, and one genotype viz., IC42531 showed a highly susceptible reaction. The average ‘r’ value ranged from 0.070 to 0.123. The highest average ‘r-value (0.123) was observed in genotypes IC42524 and EC329405, with the least average ‘r’ value in genotype EC329415 (0.070). For yield, It was found that most of the genotypes screened were potential yielders and recorded good yield despite the pathogen attack. Thus these high-yielding genotypes can be utilised in back cross-breeding along with disease resistant parent (EC 329404) to obtain resistant variety with high-yielding potential

Influence of Weather Parameters on the Incidence and Severity of Guava Scab Caused by Pestalotiopsis psidii (Pat.)

Guava (Psidium guajava) is an important tropical fruit crop of India and is known as “apple of the tropics”. It is grown and utilized as an important fruit in tropical countries like India, Indonesia, Pakistan, Bangladesh and South America. Among the biotic and abiotic diseases of guava, guava infected by scab disease [Pestalotiopsis psidii (Pat.) Mordue] is an economically important and reported average yield losses in the range of 12-18%. An experiment was conducted during 2023 at Horticulture garden, Main Agricultural Research Station, University of Agricultural Sciences, Raichur during 2023 to understand the influence of various weather parameters on the guava scab disease development. The results revealed that, irrespective of the varieties, interaction among maximum temperature, minimum temperature, maximum relative humidity, minimum relative humidity, rainy days and rainfall showed significant positive correlation with guava scab disease. And the incidence and severity of guava scab was found to be 23.21, 56.00 (Allahabad Safed), 32.45, 68.50 (Lucknow 49) and 85.00, 74.51 (Arka Kiran) respectively