Abstract
Greengram is an important protein-rich food legume crop. During the reproductive stage, high temperatures cause flower drop, induce male sterility, impair anthesis, and shortens the grain-filling period. Initially, 116 genotypes were evaluated for 3 years in two locations, and based on flowering, biomass, and yield attributes, they were grouped into four major clusters. A panel of 17 contrasting genotypes was selected for their heat tolerance in high-temperature greenhouses. The seedlings of the selected genotypes were exposed to heat shock in the range 37°C–52°C and their recovery after heat shock was assessed at 30°C. The seedlings of EC 398889 turned completely green and rejuvenated, while those of LGG 460 failed to recover, therefore, EC 398889 and LGG 460 were identified as heat-tolerant and heat-sensitive genotypes, respectively. Except for EC 398889, the remaining genotypes could not survive after heat shock. Fresh seeds of EC 398889 and LGG 460 were planted in field and pollen fertility and sucrose-synthase (SuSy) activity in grains were assessed at high temperatures. The pollen germination and SuSy activity were normal even at temperatures beyond 40°C in EC 398889 and high SuSy activity enabled faster grain filling than in LGG 460. The precise phenotyping demonstrated significant differences in the light-temperature response of photosynthesis, chlorophyll fluorescence imaging of quantum yield (Fv/Fm), and electron transport rate (ETR) between heat-tolerant (EC 398889) and heat-sensitive (LGG 460) genotypes. Molecular profiling of selected accessions showed polymorphism with 11 SSR markers and the markers CEDG147, CEDG247, and CEDG044 distinguished tolerant and sensitive groups of accessions.
Highlights
The membrane stability index was moderately high in EC 398889 as compared with LGG 460, chlorophyll index as assessed by SPAD Chlorophyll Meter Reading (SCMR) (SPAD chlorophyll meter reading) remained higher in EC 398889 at high temperature (HT) regime (Table 2)
This phenomenon was further validated by tetrazolium chloride (TTC) test as indicated by the differences in intensity of purple formazan formation when TTC solutions was added to the seedlings of EC 398889 and LGG 460 after heat shock treatment treated at 52°C for 2 h (Figures 3A, D)
Three consecutive years of field experiments using a set of 116 genotypes at two locations, namely, Vamban and Kanpur in India, differing in day length and thermal regimes led to the identification of a few promising genotypes with stable high or low yield, depending on their relative insensitivity towards photothermoperiods based on two location data
Summary
Wilczek), known as mungbean, is an important grain legume containing a high amount of digestible protein, amino acids, sugar, minerals, soluble dietary fibres, and vitamins. It is cultivated across seasons, in different environments, and in variable soil conditions in the South and South-East Asia, Africa, South America, and Australia (Parihar et al, 2017). The production is considerably influenced by changes in the photoperiod and temperature across the growing regions of greengram extending from low to high latitudes. Because greengram is a quantitative short-day plant (Chauhan and Williams, 2018), short day length at low latitude hastens flower initiation, and the plants rapidly reach the reproductive phase without adequate vegetative biomass production. Long photoperiod at high latitudes delays the onset of the reproductive phase, but the biomass is adequate and has a high leaf area index
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