Mutation spectrum of tomato, cv. First, induced by seed radiation with gamma-rays, and the subsequent partial chlorophyll deficiency

Abstract

Airdried seeds of the tomato, purebred cultivar 'First', were radiated with gamma-rays for 5 hours at varying consisting of 100, 200 and 400Gy, respectively on the distance from the source of 60Co. Seeds from all radiation treatments germinated, however, those radiated with 400Gy died thereafter, before the expansion of the first leaf. In the first generation plants (M1), seeds were obtained from 80% and 38% of plants raised from seeds radiated with 100 and 200Gy, respectively. Although pollen fertility in M1 plants was lower in 200Gy than 100Gy, complete pollen sterility was not detected, and there was no correlation between the percentage of pollen fertility and the number of seeds in the fruit. In the second generation (M2), three types of mutants were observed out of 188 lines for 100Gy; narrow leaves, low pollen fertility of less than 10%, male sterility with the same staminal cornes as the original type. On the other hand, nine different types of mutants were observed out of 88 lines for 200Gy; chlorophyll mutants-albino, viridis, xantha, and partial chlorophyll deficient, low pollen fertility, male sterility with original staminal type, with anther shrunken and brown in colour, with longer style and exerted stigma, and non germinable seeds. The results suggested that a gamma radiation dose of 200Gy to tomato seeds was effective enough to induce various types of mutants. One of the chlorophyll mutants, 'partial chlorophyll-deficient' character segregated approximately to a 3 : 1 ration of normal to deficient, which was observed in the third generation (M3) selected from self-pollinated plants in the normal phenotype of M2. This character, therefore, appears to be controlled by a single pair of recessive genes. Chlorophyll was regenerated mostly in the contracted leaves, which enabled the mutants to survive.