Jain, SandeepAnjali2019-12-142019-12-142019http://krishikosh.egranth.ac.in/handle/1/5810137673Pea (Pisum sativum L.) has wide adaptation to almost all the agro-ecological zones of India and is 2ndmost widely cultivated crop in Punjab after potato. Three distinct syndromes viz., leaf spot; leaf blight and pod spot and foot rot were recognized and distinguished in pea field and their primary pathogenic causes were established. All the three symptom-types were more prevalent in Western plain zones with incidence and severity of 56.90 and 23.35 per cent followed by sub-mountainous zone i.e. 49.12 and 21.48 per cent, respectively. The overall mean disease incidence of Punjab state was recorded to be 33.99 and 37.46 per cent during the year 2017-18 and 2018-19, whereas disease severity was 13.78 and 5.78 per cent respectively during the same years. Among the different varieties grown in field, maximum mean disease incidence (58.20%) and severity (25.28%) recorded on AP-3 followed by MA-7 i.e. 55.24 and 23.22 per cent, respectively. Pathogenicity tests were conducted to prove the Koch‟s postulate and identification of species associated with distinct symptom-types was done through morphological and molecular studies. All the isolates of pea blight were significantly variable from each other with respect to colony colour, colony texture, colony form and margin, mean radial growth (mm), spore size and sporulation intensity. Average conidial size ranged from 4.12-12.30 (L) x 2.09- 4.37(B) μm with mean average size of conidia 6.19- 6.49 (L) x 3.27-3.66 (B) μm. Smallest conidia length (4.02 μm) was observed in isolate PB-11 and the longest conidia were recorded in isolate PB-1(11.03 μm). All the isolate cultured on PDA medium produced average sporulation of 6.21 x106 pycniospores/ml. The pathogen associated with leaf blight and pod spot type of symptoms was identified as Didymella pinodes which was found to be the most prevalent pathogen species. This was followed by foot rot type of symptoms caused by Phoma pinodella. The pathogen associated with leaf spot type of symptom was identified as Ascochyta pisi. This pathogenic species was least prevalent among the three identified species of pea blight. Thirty isolates of pea blight were categorized on the basis of pathological aggressiveness of different components viz., area under disease progress curve (AUDPC), incubation period (IP50), latent period (LP), lesion size (LS), percentage of stem girdling (%HTM) and number of girdled internodes (NOI) using seven pea cultivars. Hierarchical cluster analysis of these aggressiveness components categorized isolates into three distinct groups. Isolate PB-27 was found to be highly aggressive followed by PB-30 whereas isolate PB-1 was the least aggressive. Logistic model gave the best fit for disease progress of pea blight. Out of 100 genotypes evaluated, only 5 genotypes namely Eddy, PS-24, Arya Veer, CHPMR-2 and PS-19 showed resistant reaction against pea blight complex and can be used as a donor in pea blight resistance breeding programme. This is the first systematic study on etiology and comparative aggressiveness pathogen associated with pea blight complex in Punjab.ennullThesis