Physiological and Stress Studies of Different Rapeseed- Mustard Genotypes Under Terminal Heat Stress

Rapeseed-mustard constitutes an important source of edible oil next to soybean, grows under diverse agro ecological situations such as timely / late sown, rainfed / irrigated, sole-& / or mixed crop with cereals (wheat, barley etc.) and rabi (October-April) pulses (chickpea, lentil etc.), where high temperature is the main constraint not only at germination but also at grain filling stage. Flowering and grain filling are the most sensitive stages for temperature stress damage probably due to vulnerability during pollen and grain development, anthesis and fertilization leading to reduce crop yield. Effects of heat (high temperature) stress during terminal stage were investigated on photosynthesis, transpiration, stomatal conductance, stress intensity, mean productivity and geometric mean productivity , yield attributing characters and seed yield of 43 germplasm of rapeseed-mustard during 2010-11. Forty three rapeseed-mustard genotypes were sown in the field at two dates of sowing i.e., 1 optimum, D1 (Oct. 26, 2010) and 2 in the last week of November, D2 (November 26, 2010) to allow the crop exposure to high temperature at terminal stage viz., grain filling stage. The crop sown in late November faced average maximum temperature of > 30C at grain filling stage. Genotypes were sown in augmented design. The stress intensity varied from 011 (BPR 349-9) to 0.82 (RH 304) While tolerance ranged from 1.05 (BPR 349-9) to 16.8 (EJ 17). Among the 43 genotypes, BPR349-9, PLM 2, RGN 197, RK 08-02 and BPR 549-9 had low stress intensity and tolerance. Terminal heat stress adversely effected photosynthesis and caused appreciable reduction from 9.8 (JS-29) to 48.3% (PBR-378) over the normal sown genotypes. The genotypes JS-29, KM-26, RMM-09-02 and PBR-357 134 Maharaj Singh, S.S.Rathore and P.Raja showed < 15% reduction in photosynthesis under high temperature stress. The genotypes EJ-22, EJ-20, NPJ-124, NDT-05-02 showed less reduction in seed yield because of escape high temperature at terminal stage due to earliness. While the genotypes, BPR-549-9, BPR-540-6 and BPR-349-9 showed < 20% reduction in seed yield with high 1000seed weight. All these genotypes showed superiority over both the checks (BPR 541-4 and JD-6). The study revealed that genotypes, BPR-549-9, BPR-540-6 and BPR-349-9 showed tolerant to high temperature at terminal stage based on less reduction in seed yield, low stress intensity, medium transpiration rate. Besides, this studies the other research done at DRMR, Bharatpur revealed superiority of these genetic stocks for high temperature tolerance at juvenile stage and salinity. On the basis of these studies BPR 349-9was identified and got registered for high temperature tolerance at juvenile stage. BPR 540-6 (IC 0593927; INGR 13027)for salinity and high temperature tolerance at juvenile stage. While BPR 549-9 (IC 0595525; INGR 13016)was registered for salinity tolerance at juvenile stage and high water use efficiency. Thus these genotypes can be used to breed for high temperature tolerance. KeywordsStress intensity, stomatal conductance, water use efficiency, mustard