Effect of High Temperature on Pollen Viability and Reproductive Organs of Tomato (Lycopersicon Esculentum Mill).

High temperature is most critical factor which can affect the pollen production, pollen viability and other reproductive mechanisms in tomato because reproductive structures of the tomato plants are highly responsive to temperature. Hence the present studies were conducted to evaluate the genotypes which are heat tolerant for further use in heat stress tolerance breeding programs, and increase the production span of the crop, which is in fact sandwiched between very high and very low temperature regimes can be increased. Sixteen genotypes comprising of released varieties, hybrids/advanced generations breeding lines and exotic introductions were evaluated in completely randomized block design with three replications. Splitting of anther cone is a morphological abnormality of the flower in some genotypes at high temperature and it also leads to evasion of self pollination by disrupting the channels for pollen transfer to the stigma, consequently leading to low fruit setting. It is also well documented that genotypic differences exist for degree of splitting of anther cone which is ultimately reflected in fruit setting percentage. The minimum (26.54 %) and maximum (72.68 %) percentage of splitting of anther cone was recorded in the genotype UC 82 B & Nagcarlan, respectively. Stigma exsertion leads to evasion of self pollination and consequently resulting in low fruit setting percentage. The minimum (11.31 %) and maximum (80.67 %) of stigma exertion was recorded in the genotype P 3-1-7-1 and P 2-6-1-1, respectively. The difference among heat tolerant and heat sensitive cultivars for fruit setting ability to their ability of producing viable pollen under high temperature. The maximum pollen viability of 77.43 per cent was recorded in line EC 50534-1-1 and the minimum pollen viability was 9.84 per cent in the genotype CR-2P-8-5-1. High pollen germination under high temperature conditions is also one of the indicators of inherent heat tolerance. The minimum pollen germination was 4.44 per cent in the genotype UC 82 B whereas, the maximum pollen germination of 73.87 per cent was recorded in the line EC 50534-1-1. The observations on anther dehiscence were started at 5.15 am and continued in successive rounds till dehiscence was accomplished in all the genotypes. Dehiscence was accomplished invariably between 6.00 a.m. and 6.20 a.m. irrespective of the genotype. The study revealed that high temperature affects all the above said characters and consequently fruit set. There are some genotypes which in spite of high stigmatic exsertion and splitting of anther cone bore good fruit yield. This may be attributed to high pollen viability and their high pollen germination as recorded in fresh samples. Here it is worth mentioning that all the factors contribute to fruit set and no individual factor can depict the total fruit set and its tolerance to high temperature. These studies offer possibility of using these promising genotypes for further breeding programs to evolve heat stress tolerant varieties for their supplementary/complementary allele.