High temperature during the reproductive stage in chickpea (Cicer arietinum L.) is a major cause of yield loss. The objective of this research was to determine if that variation can be explained by differences in anther and pollen development under heat stress. Therefore the effect of high temperature during the pre-and postanthesis periods on pollen viability, pollen germination in a medium, pollen germination on the stigma, pollen tube growth and pod set in a heat tolerant (ICCV 2 92944) and a heat sensitive (ICC 5912) genotype was studied. The plants were evaluated under heat stress and non-heat stress conditions in controlled environments. High temperature stress (29/16˚C to 40/25˚C) was gradually applied at flowering to study pollen viability and stigma receptivity including flower production, pod set and seed number. This was compared with a non-stress treatment (27/16˚C). The high temperatures reduced pod set by reducing pollen viability and pollen production per flower. The ICCV 92944 pollen was viable at 35/20˚C (41% fertile) and at 40/25˚C (13% fertile), while ICC 5912 pollen was completely sterile at 35/20˚C with no in vitro germination and no germination on the stigma. However, the stigma of ICC 5912 remained receptive at 35/20˚C and non-stressed pollen (27/16˚C) germinated on it during reciprocal crossing. These data indicate that pollen grains were more sensitive to high temperature than the stigma in chickpea. High temperature also reduced pollen production per flower, % pollen germination, pod set and seed number.
High temperature during reproduction is a major factor limiting the yield of chickpea (Cicer arietinum L.). Observations in the field from late season experiments (Feb-2 May) and various high temperature regimes generated in controlled environments showed clear genetic variation in male reproductive tissue (anther and pollen), its function (pollen germination and tube growth) and pod set. Greater pod setting ability of heat tolerant genotypes (ICC 1205 and ICC 15614) compared to heat sensitive genotypes (ICC 4567 and ICC 10685) was observed in both the field and controlled conditions. Both anthers and pollen showed more structural abnormalities under stress such as changes in anther locule number, anther epidermis wall thickening and pollen sterility, rather than function (e.g. in vivo pollen tube growth). The critical temperature for pod set was ≥ 37˚C in heat tolerant genotypes (ICC 1205 and ICC 15614) and ≥ 33˚C for heat sensitive genotypes (ICC 4567 and ICC 10685). Overall, pod set showed greater sensitivity in the controlled environments where a 67% reduction was observed at ≥ 34/19˚C compared to the control (27/16˚C). In the field, a pod set reduction of more than 50% occurred at high ambient day temperature (36˚C) and the stigma was still receptive at 40.2/25.5˚C. In contrast, under controlled conditions the stigma was still receptive at 35/20˚C in four genotypes. Clearly, chickpea pollen grains are more sensitive to high temperature than the stigma in both the field and controlled environments. Among the four genotypes tested, ICC 1205 was the most heat tolerant and ICC 4567 was the most heat sensitive.
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