Effect of gamma ray irradiation and cryopreservation on pollen stainability, in vitro germination, and fruit set in Citrus

The present work analyzed the stainability and in vitro germinability of the gamma-ray-irradiated fresh and cryopreserved pollens of 3 Citrus species: C. limon, C. limetta, and C. sinensis. Fruit set after pollinating 75 flowers of C. grandis with irradiated and nonirradiated (control) fresh and cryopreserved pollen was also assessed. Results showed that in solid and liquid culture media the highest in vitro germination values were detected in fresh (61.45% and 62.53%, respectively) as well as cryopreserved (53.17% and 55.36%, respectively) C. sinensis nonirradiated pollens. However, at a higher irradiation dose of 500 Gy in both culture media, the minimum reduction of germinability of fresh (30.85% and 28.01%) and cryopreserved pollens (33.37% and 31.06%) was found in C. limon. Contrary to in vitro germination, the minimum reduction in stainability of fresh and cryopreserved pollens, as assessed by acetocarmine (9.51% and 11.85%, respectively) and FDA tests (10.78% and 12.73%, respectively), was recorded in C. limetta. Regardless of irradiation dose, the highest fruit setting in C. grandis at 40 days after pollination was detected when it was pollinated with both fresh (38.02%) and cryopreserved (34.92%) C. limetta pollen grains.