Studies on Genetic Basis and Molecular Mechanisms of Spot Blotch [Bipolaris sorokiniana (Sacc.) shoemaker] Disease Resistance in Tetraploid Wheat Species
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Date
2017-04
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University of Agricultural Science, Dharwad
Abstract
The present investigation was carried out during rabi, 2014-15 at the Agricultural Research Station (ARS), Arabhavi, UAS, Dharwad. The six generation (P1, P2, F1, F2, B1 and B2) mean analysis was used to study the gene action for spot blotch disease resistance in four durum and two dicoccum crosses. High GCV, PCV, heritability and GAM were observed for seed yield, disease severity and AUDPC. The disease severity (%) and AUDPC were negatively associated with seed yield and its components. The duplicate gene action and additive × dominance genetic effects were played an important role in genetic control of spot blotch resistance. The higher percentage of transgressive segregants for disease resistance was observed in F2 population of durum cross Bijaga Yellow × NIDW-295 (15.56 %) and in dicoccum cross DDK-1025 × DDK-50044 (11.00 %).
The highly susceptible Bijaga Yellow and resistant NIDW-295 genotypes were analyzed for host pathogen interaction studies at histopathological and molecular level. The infection pattern of Bipolaris sorokiniana at different time points after inoculations was studied. The histopathological studies revealed that six host resistant components viz., number of trichomes on leaves, number of spore per lesion, spore germination, lesion size and lesion frequency were differed in resistant and susceptible genotypes. The expression stability of five housekeeping genes were analyzed by Bestkeeper, gNORM, NormFinder and comprehensive ranking methods suggested that CDC 48 was found most stable and used as reference gene for quantitative RT-PCR. The relative expression profiling of defense related genes during spot blotch infection were analyzed and showed significant up regulation of pathogenesis related (PR) genes, salicylic acid, jasmonic acid, ethylene biosynthesis and transcription factor genes at early stages of infection in NIDW-295 (Resistant) compared to Bijaga Yellow (Susceptible) implying their role in the defense response against spot blotch infection in tetraploid wheat.