Search

Scab disease caused by Venturiaspp. is a major threat to pome and stone fruit crops which are grown extensively under the temperate climate of Jammu and Kashmir in India, affecting economy of commercial growers. To gain insights into the establishment and spread of the pathogen, it is essential to have a clear understanding of its life cycle, in which the presence or absence of the sexual stage holds considerable importance. The in-vivoand in-vitromorphological differentiation of three Venturiaspecies viz.; Venturia inaequalis, Venturia pyrina, Venturia carpophilarevealed that there were significant differences within their morpho-cultural characteristics. However, Venturia carpophilainfecting both almond and peach showed insignificant variations in both in vivo and in vitro conditions. Importantly, the teleomorph was only observed in V. inaequalis, which emphasizes that there might be high genetic variation in the pathogen population. Surprisingly, no teleomorph of V. pyrinaand V. carpophilawas found, which may be related to the fact that both of these pathogen species overwinter as dormant mycelia and conidia under temperate conditions of North Western Himalayas.

Apple scab instigated by Venturia inaequalisimpels remarkable losses to apple fruit production. In an effort to comprehend the key mechanisms of evolutionary potential defining V. inaequalispopulation, 132 isolates of V. inaequalisfrom five commercial apple orchards were collected and assayed using 14 microsatellite markers. The average diversity was observed within the individuals of populations based on the Shannon-Wieners index (I) and observed heterozygosity (Ho) was average but considerably lower than expected heterozygosity (He). The genetic differentiation based on FST values was revealed as an average measure of divergence between populations and had varying proportions of gene flow and migration among themselves. Analysis of Molecular Variance (AMOVA) revealed that variance (94%) was dispersed across individuals with a significant (6%) variation between populations from different regions. To examine host specialization within the V. inaequalispopulation, the assignment approach based on K-means of clustering (an unsupervised machine learning approach), revealed that the clustering method supported three clusters at (K= 3) and three major clusters were also observed in Principle Component Analysis (PCA). Additionally, Nei’s genetic distance values, pairwise estimates of genetic differentiation, dendrogram using the neighbor-joining and PCoA revealed the random distribution of V. Inaequalisisolates that depicted a high proportion of genotypic diversity within populations and population genetic structure.