Elucidating genetic variability and population structure in Venturia inaequalis associated with apple scab diseaseusing SSR markers

Abstract

Apple scab caused by Venturia inaequalis Cooke (Wint.) is one the important diseases of trade and industrial significance in apple. In present study variability studies in pathogen isolates were studied, which is one of the most important factors for devising management studies of scab disease in apple. Genetic diversity of 30 Venturia inaequalis isolates from 12 districts of two geographical distinct regions of Jammu and Kashmir was calculated based on the allele frequencies of 28 SSR markers and the internal transcribed spacer (ITS) region of the ribosomal DNA. The ITS based characterized sequences were submitted to NCBI GenBank and accession numbers were sanctioned. Dendrogram showed that all the accessions formed 2 main clusters with various degree of sub clustering within the clusters. Analysis based on SSR study reveals that the heterozygosity ranged from 0.0 and 0.5, with an average value of 0.39. The expected heterozygosis or gene diversity (He) ranged from 0.0 to 0.50 with an average of 0.40. The Fst value ranges from 0 to 0.6 with an average of 0.194. Diversity within each population (HS) values ranging from 0.26 to 0.33. Average differentiation among populations (GST) was 0.11 and populations were isolated by significant distance (r 2 = 0.50, P < 0.01). From the AMOVA analysis, 25% of variation was observed among population, 9% among individuals and 66% within individuals observed in the population. Structure analysis grouped isolates into two populations. Principle coordinate analysis explained variation of 36.6% in population 1, 14.30% in population 2 and 13.10% in population 3(Admixture) with 64.07% as overall cumulative percentage of variation. This indicates that extensive short-distance gene flow occurs in Kashmir region that dispersal over longer distances also appears to occur frequently enough to prevent differentiation due to genetic drift. Also it is evident that Jammu and Kashmir most likely has V. inaequalis subpopulations linked to diverse climatic conditions of the Jammu region compared to the mountainous inland Kashmir region. The results of present study would help to understand the genetic diversity of V. inaequalis from Jammu and Kashmir that would lead in the development of more effective management strategies and development of new resistant cultivars through marker-assisted selection.

Bacterial Endophyte Community Dynamics in Apple (Malus domestica Borkh.) Germplasm and Their Evaluation for Scab Management Strategies

“…The area in Jammu and Kashmir utilizes 136.54 thousand hectares for its apple production. Annual production reaches 1672.72 thousand metric tons and productivity of 12.50 tons per hectare [2,3].…”

“…In the Jammu and Kashmir state, this disease was reported in 1970s and ever since, it has caused havoc in the apple industry with the extent of fruit loss of up to 60%, estimating an amount in hundreds of crores [4]. V. inequalis, being a heterothallic haploid ascomycete, reproduces both sexually and asexually [3][4][5][6]. The disease takes the severe form in regions in which recurrent rainfall through the spring seasons leads into ascospore emancipation and infection [5].…”

Genetic diversity of Venturia inaequalis isolates (Apple scab) in China and U.K. determined by SSR markers

“…A recent study showed that Jammu and Kashmir most likely had V . inaequalis subpopulations linked to diverse climatic conditions of the Jammu region compared to the mountainous inland Kashmir region [ 20 ]. Based on this study, the diversity of the pathogen population mainly comes from individuals.…”

Quantification of polyphenolic compounds and relative gene expression studies of phenylpropanoid pathway in apple (Malus domestica Borkh) in response to Venturia inaequalis infection

“…Apple scab caused by Venturia inaequalis, a filamentous fungus, is one of the most detrimental fungal pathogens that remain a major threat to apple production worldwide ( Mansoor et al, 2019 ). It is among the most noteworthy threats to apple growing areas situated in the regions where climate is cool ( MacHardy, 1996 ).…”

“…Saprophytic (sexual state Venturia inaequalis (Cke) and parasitic (asexual state Spilocaea Pomi Fr) are the two states of this fungus. Damage caused by this pathogen are developed in between the cuticle and the cell wall of epidermal layers ( MacHardy, 1996 , Mansoor et al, 2019 ).…”