Evaluation of rice (Oryza sativa L.) genotypes of North Eastern Hill Region (NEHR) for traits associated with anaerobic germination.
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Date
2022-10
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College of Post Graduate Studies in Agricultural Sciences, Central Agricultural Univerity, Imphal
Abstract
Direct seeding is recently becoming increasingly popular among rice producers because of its ease of cultivation, economic benefits, early crop maturity, and greater yield. However, around one-third of all rice produced globally is grown in flood-prone locations, making flooding the third biggest source of stress that impedes rice production. Anaerobic germination (AG) which refers to a seed's innate ability to germinate under oxygen deficiency by acquiring the necessary energy through anaerobic respiration is a crucial characteristic for enhancing direst seeded rice. Reports of high yielding varieties tolerant to anaerobic germination are few, hence it is important to evaluate the rice genetic diversity to develop variety with these characteristics. It would also enable flooding the field during the earliest stages of germination as a successful weed control technique. In the present study, a set of 60 rice genotypes, which were collected from different parts of the North Eastern Hill Region was screened for various traits associated with anaerobic germination. A preliminary nursery evaluation of morphological traits showed significant variation among the set of genotypes for all the traits (speed of germination, germination percentage, visual scoring of seedling vigour, shoot length, thickness of stem, number of leaves, leaf area index). Anaerobic experiment was designed to screen the genotypes under the anaerobic condition with 8 cm of submergence as well as a controlled set-up. The observations were recorded till 21 days after sowing. All the morpho-physiological parameters (seedling vigour index, germination percentage, speed of germination, survival percentage, shoot length, root length, fresh weight, dry weight, number of leaves) showed high significant genotype x treatment (anaerobic and control conditions) interaction suggesting that there is a significant variance in the genotypes with respect to submergence. The correlation study did not reveal significant correlation between traits under nursery and anaerobic condition except for shoot length (r=0.43) and number of leaves (r=0.32). Amongst the traits studied under anaerobic treatment, seedling vigour index-II showed significant and positive correlation with 11 other anaerobic traits namely seedling vigour index-I (r= 0.94), speed of germination (r= 0.88), survival percentage (r=0.84), germination percentage (r= 0.79), relative germination percentage (r= 0.46), number of leaves (r= 0.43), fresh weight (r= 0.38), dry weight (r= 0.34), root length (r=0.33), plant portion above water (r = 0.32) and shoot length (r = 0.31). PCA registered a cumulative variation of 63.3 % from the first two PCs, with PC1 accounting for 42.9% and
PC2 accounting for 20.4 % of the total variation. Based on PCA, contrasting genotypes were identified, where four were identified as tolerant (Lakang Baso, Sahbhangi Dhan, CAUS 107 and CAUS 123) and the rest as susceptible (BLM, Chakhao Poireiton, Phourel and Mailung). The alpha amylase and peroxidase enzyme activity in the selected genotypes showed significant and considerable variation among genotypes. The tolerant genotypes showed higher alpha amylase activity with an average of 228.51 μmol/min as compared to the susceptible ones (77.15 μmol/min). The correlation study revealed that there is a positive correlation between alpha amylase activity and all the 13 anaerobic traits, in which, survival percentage (r= 0.84), number of leaves (r= 0.93), speed of germination (r= 0.76), germination percentage (r= 0.77), relative germination percentage (r= 0.72) and anaerobic germination index (r= 0.73) showed a significant and positive correlation. However, there was no significant correlation between peroxidise activity and any of the nursery traits or anaerobic traits. The traits such as seedling vigour index, survival percentage, germination percentage, shoot length and alpha amylase activity were amongst the promising indicators for tolerance to germination under anaerobic conditions. The identified contrasting genotypes in the study could be a valuable resource for future breeding programs.