Effect of gamma ray irradiated pollen technique on seed development pattern in Citrus

In modern fruit breeding, to reduce the breeding cycle, induction of haploid plants through irradiated pollen technique is of paramount importance. However, the major drawback is the sensitivity of pollen to higher irradiation doses as it induces abnormality in double fertilization process. Hence, optimization of irradiation doses for maximum recovery of healthy seed is very important. Present work analyzed the seed developmental pattern of Citrus grandis, pollinated with gamma irradiated pollen (100-500 Gy) of C. limon, C. limetta, and C. sinensis. Not a single fruit was retained on the tree till maturity in C. grandis × C. limon crosses; however, in other two cross combinations, fruits were harvested at maturity only up to 300 Gy irradiation doses. Among the harvested fruit, normal seed decreased gradually with increasing irradiation doses and less than 5 normal seeds per fruit were obtained at 300 Gy with maximum in C. grandis × C. limetta cross. However, abnormal and empty number no. of seeds has increased significantly with increasing irradiation doses. Developmental pattern of embryo and endosperm within normal seeds was also influenced significantly by irradiation treatment. At higher doses, seeds number with both embryo and endosperm was decreased gradually and at 300 Gy, it was reduced to 59.47% as compared to control.