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Author: Chetan V. N. × Start date: 2020 × Thesis Type: M.Sc ×
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    Factors affecting aggressiveness of Sclerotinia sclerotiorum (Lib.) de Bary inciting stem rot of rapeseedmustard
    (Punjab Agricultural University, Ludhiana, 2022) Chetan V. N.; Sandhu, P S
    The stem rot caused by Sclerotinia sclerotiorum (Lib.) de Bary is one of the major diseases of rapeseed-mustard. In this study, factors affecting aggressiveness of the pathogen were evaluated using isolates collected from various rapeseed-mustard growing regions of India. These isolates were estimated for development of the disease, oxalic acid production, total cellulase and cutinase activity. These isolates were significantly different w.r.t. their aggressiveness which highly correlated with oxalic acid production and cutinase activity and moderately with total cellulase activity. Low and high aggressive isolates were sequenced to detect variation in genes Sscut and Ssoah1. No variation was seen in Sscut while Ssoah1 showed 7 synonymous SNPs. Further study was conducted to test the efficacy of alkali salts such as sodium carbonate (SC), potassium silicate (PS), sodium propionate (SP) and calcium propionate (CP) against Sclerotinia stem rot. Under in vitro conditions, the PDA media amended with SC (0.6-1 per cent), PS (0.8-1.2 per cent), CP and SP (1.6-1.8 per cent) showed complete mycelial growth inhibition when compared with un-amended PDA medium. In case of detached leaf assay, SC @ 1 per cent, PS @ 1.4 per cent, SP @ 1.8 per cent and CP @1.8 per cent were effective in inhibiting lesion development of pathogen when compared to untreated leaves. Effective treatments were tested under field conditions at two locationswhere different treatments were sprayed with different alkali salts 2 days before the inoculation. The pooled data of both the locations revealed that CP @ 1.8 per cent showed highest percent reduction in mean lesion length (63.35 per cent) followed by SP @1.8 per cent with 57.77 per cent reduction. The yield data showed negative correlation with lesion length which implies significant reduction in yield of control as compared to treatments.