Virulence profiling, host plant resistance and management of fusarium wilt of pigeonpea

Pigeonpea wilt caused by Fusarium udum is the most important soil borne disease and a main constraint in boosting the yield. The survey conducted in Southern and Central part of India during Kharif 2013-14 and 2014-15 indicated, an incidence ranging from 0.0 to 45.33 per cent during 2013-14 and 0.0 to 70.80 per cent during 2014-15. Disease occurrence was observed irrespective of cropping system, soil types and least wilt incidence was recorded in improved cultivars (TS- 3R, Asha) rather than local cultivars. 111 Fusarium isolates were collected to study the cultural, morphological, molecular and pathogenic variability. The virulence profiling of 72 isolates of F. udum on 11 host differentials, resulted in four groups such as avirulent, least virulent, moderately virulent and highly virulent ones. Based on wilt incidence and reaction of F. udum isolates on four pigeonpea host differentials (ICP 2376, C- 11, ICP 8863 and ICP 9174), 67 virulent isolates were categorised into six variants viz., Variant 0, Variant I, Variant II, Variant III, Variant VI and Variant VII. Variant VI and VII are the new variants identified in present study. Under proteomic study 141 differentially expressed proteins spots were noticed in resistant and susceptible cultivars in F. udum and pigeonpea interaction. Of them, 12 were successfully characterized by using MALDI TOF MS/ MS. The identified proteins belong to seven functional groups viz., metabolism related proteins, biosynthetic process related, defense related, redox homeostasis proteins, signalling protein and a pathogen cell wall protein. This is the first piece of work on pigeonpea wilt proteomics. Out of 52 genotypes screened, 12 were resistant, 14 were moderately resistant, 11 were moderately susceptible and 15 were showed susceptible reaction. The highest vigour index of moderately resistant (BMR-736) and susceptible cultivar (ICP 2376) was recorded in P. fluorescens (RP- 46) + P. putida (RP- 56) treated seeds. The maximum activity of defense related enzymes like, PO, PPO and PAL was recorded in seeds treatment with Pseudomonas fluorescens (RP- 46) and challenged with F. udum (FU- 37). Under glasshouse, condition seed treatment with P. fluorescens (RP- 46) recorded least wilt incidence (8.34 %) in moderately resistant cultivar (BSMR- 736) and 29.17 per centin susceptible cultivar (ICP 2376). Captan among non-systemic fungicides, carbendazim and benomyl among systemic fungicides and Trichoderma harzianum (Th-R) among the bio-agent were effective under in-vitro selected for disease management under field condition. Based on two years performance of treatments, soil drenching with 0.3 per cent carbendazim fungicide recorded significantly lowest mean wilt incidence of 6.18 per cent with highest yield of 1688 kg per ha with the next best treatment by seed treatment @ 4 g per kg seeds + soil application of PGPR consortium @ 25 kg per ha in FYM @ 50 kg per ha, with a wilt incidence of 8.80 per cent and yield of 1567 kg per ha