Cultural variability and germplasm screening against Bipolaris sorokiniana (Sacc.) Shoemaker causing spot blotch disease in bread wheat (Triticum aestivum L.)
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Date
2021-09
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Wheat (Triticum aestivum L.) is one of the most nutritious and basic staple food crop and is widely cultivated cereal grain in the world. In India spot blotch disease caused by Bipolaris sorokinana (Sacc.) Shoemaker is reported to be important foliar disease causing yield loss ranging from 15-50 per cent. It is one of the most important diseases of wheat in North Eastern Plains Zone (NEPZ) representing warm and humid climate in India. Spot blotch was earlier thought to be minor disease but due to global climate change it is also increasing in North Western Plains Zone (NWPZ), Peninsular and Central zone of India. The present investigation was carried out with following objectives: (i) Screening of wheat germplasm against spot blotch for identification of sources of disease resistance under epiphytotic conditions. (ii) Study the role of agronomic traits on spot blotch resistance resistance (iii) Assessment of Area Under Disease Progress Curve (AUDPC) and Infection rate (iv) Study the Cultural- morphological variability of Bipolaris sorokiniana under in-vitro condition. The study was conducted during 2019-20 and 2020-2021 and the experimental material comprised of 192 germplasm accessions along with four checks, Chirya 3 and Francolin (resistant) HD3086 & HD2967 (susceptible). The fifty three germplasm accessions out of 192 were found to be phenotypically resistant and had lower AUDPC values. Therefore, selection of cultivars having lower AUDPC values is acceptable for practical purposes. These genotypes were evaluated in randomized block design (RBD) in 2020-2021 and observations were recorded for six characters viz., disease severity, days to 75% heading, days to maturity, plant height, spike length and thousand grain weight. Simultaneously, correlation analysis of these agronomic traits revealed that days to maturity, days to heading, plant height were negatively correlated with AUDPC whereas, spike length and test weight were positively correlated. The pathogen Bipolaris sorokiniana was isolated from the leaf samples collected from eight locations in Uttarakhand (Pantnagar, Sitarganj, Khatima, Nanakmatta, Kashipur, Rudrapur, Gadarpur and Haldwani). The cultural and morphological studies of these isolates were done under in-vitro conditions, which revealed a distinct variation in colony morphology as well as conidial characteristics in all the eight isolates. The information on cultural and morphological variability existing in the pathogen (Bipolaris sorokiniana) can be utilized by breeders and pathologists for resistance breeding and the aggressive isolates can be used for creating epiphytotic conditions. The resistant accessions can be used by breeders for the development of spot blotch resistant varieties.