Screening of wheat germplasm for terminal heat tolerance under hyper-arid conditions

Abstract

Due to intensive cropping system, late planting of wheat is very common which causes plants to suffer due to terminal heat stress. To adapt and mitigate the adverse effect of heat on wheat, researchers want to develop heat-tolerant wheat genotypes. Therefore, a set of 11 germplasms of wheat was sown in normal period (November 25) as well as in late period (December 25) at Instructional Farm of Swami Keshwanand Rajasthan Agricultural University, Bikaner. Various physiological, gas exchange and yield attributes were measured at different crop growth stages. Results showed that days to anthesis (DTA), relative water content (RWC), membrane stability index (MSI), photosynthetic pigments, photosynthetic rate (A), stomatal conductance (gs), internal CO2 concentration (ci), water use efficiency (WUE) and yield attributes were reduced, whereas transpiration rate (E) was increased under late sown as compared to normal. Most of the physiological and yield characters showed superiority (highest/lowest) in germplasm entry no. 26 followed by 43 and 58. Heat susceptibility index (HSI) was the lowest, whereas chlorophyll stability (CSI) and heat tolerance index (HTI) were the highest recorded in entry 26 followed by 43. Heat-tolerant germplasm could be selected on the basis of high RWC, MSI, photosynthetic pigments, CSI, A, gs, ci, WUE, yield components and HTI, and low E and HSI. In the present investigation, entry no. 26 (IC279317), 43 (IC335971) and 58 (IC336816) were found the best suited germplasm under heat stress. These germplasms supposed to carry the heat-tolerant genes and may be used for further heat tolerance breeding.