Virulence and Molecular Diversity of Venturia inaequalis in Commercial Apple Growing Regions in Kashmir

Abstract

Seventy‐one isolates of Venturia inaequalis collected from commercial apple growing areas of Kashmir were characterized on international differential apple hosts and analyzed by Random Amplified Polymorphic Microsatellites (RAMS), PCR–RFLP and sequencing of rDNA for elucidation of variability. Virulence analysis on a differential set categorized them into four pathogenic races, viz. (0), (1), (2) and (1,2) in the first time comprehensive molecular analysis of this in India and especially from Jammu and Kashmir, a north‐western Himalayan state of India. Race groups (0), (1), (2) and (1,2) contained isolates from diverse areas without specificity to any geographical zone or region. Cluster analysis of the RAMS and PCR–RFLP revealed a high genotypic diversity within V. inaequalis isolates. Three major clusters were obtained and the isolates could not be categorized on the basis of either their geographical distribution or the cultivar from which they were isolated. amova analysis of pathogen populations at regional or race level revealed high diversity within the populations. Pairwise FST comparisons between the populations revealed less genetic differentiation, thereby indicating existence of frequent gene flow in Kashmir. The 24 rDNA sequences of V. inaequalis showed high haplotype diversity of 0.938 and 0.40 nucleotide diversity. Again clustering at regional or race level detected greater part of variability within groups than among groups, thereby indicating high diversity in V. inaequalis populations in Kashmir valley.

Distribution of Apple Scab Race Flora and Identification of Resistant Sources against Venturia inaequalis in Kashmir

“…This shift in pathogenicity was not exhibited by the isolates collected during 2014. These isolates were collected after three years of our previous study (Padder et al, 2013) which may be attributed to the less time lapse in survey or the absence of scab resistance genes (Rvi3 to Rvi13) in the orchards of Kashmir valley. Additionally, V. inaequalis is described as a good model for host adaptation in plant pathogens (Giraud et al, 2010) because mating only occurs between strains that are able to infect identical hosts, thus facilitating the maintenance of adaptations to a host when host ranges do not overlap (Guerin and Cam, 2004;Guerin et al, 2007;Gladieux et al, 2011).…”

“…Elucidation of virulence structure showed four distinct races viz., (0), (1), (2) and (1, 2) in Kashmir. Population structure based on RAPD, ISSR and CAPS revealed low genetic differentiation in the different scab pathogen population's thereby indicating occurrence of frequent gene flow in the region (Padder et al, 2011(Padder et al, , 2013. This information is a vital component for deployment of resistant cultivars spatially, in organic farming and of any integrated pest and disease management program.…”

“…It is the most important disease of apple in Kashmir, a North Western Himalayan state of India. Like other apple growing regions worldwide, scab is currently being managed by fungicidal sprays from pink bud to harvest in the State (Padder et al, 2013). Public concerns over pesticide residue in food have generated a great deal of interest in reducing fungicide use on all food crops.…”

“…This information is a vital component for deployment of resistant cultivars spatially, in organic farming and of any integrated pest and disease management program. Study under investigation was designed with the following objectives to (1) Assess the pathogenic variability in V. inaequalis with an aim to identify any shift in virulence pattern from the already reported races in the region (Padder et al, 2013), (2) Distribute the apple scab race flora (from the present investigation and previously reported) spatially in commercial apple growing regions of Kashmir valley and (3) Evaluate apple genotypes against each individual race under controlled conditions with an intention to identify scab resistant cultivars and their distribution/deployment in time and space. Padder et al (2013) revealed the existence of 4 races viz., (0), (1), (2) and (1, 2) within the 71 of isolates.…”

Non- Chemical Management of Apple Scab- A Global Perspective

“…Like other apple growing regions worldwide, scab too is currently being managed by fungicidal sprays from pink bud to harvest in Jammu and Kashmir state of India. (Padder et al, 2013).Until recently, it was perceived as the only economical control measure. This perception is changing as a result of the high costs of new molecules such as the strobilurine-based fungicides, increased fungicide resistance in populations of V. inaequalis, and increased appreciation of environmental costs and consumers negative perceptions of fungicide use (Beresford and Manktelow, 1994).…”