Irradiation effects of ⁶⁰Co-γ rays on different cotton varieties and the screening of drought tolerant mutants

In order to study the irradiation effects of⁶⁰Co-γ rays on different cotton varieties and screen drought-tolerant mutants. Three different cotton varieties (Lu Mian 532, K638 and K836) were irradiated by 250 Gy of ⁶⁰Co-γ rays. Results showed that ⁶⁰Co-γ rays irradiation significantly decreased the germination rate, germination potentiality and emergence rate of the three cotton varieties. Compared to non-irradiation the germination rate, germination potentiality and emergence rate of K836 were decreased by 38.9, 45.9 and 48.5%, respectively, and those decreased were greater than in Lu Mian 532 and K638. ⁶⁰Co-γ rays irradiation significantly decreased the photosynthetic rate (Pn), transpiration rate (Tr) and chlorophyll content (Chl), cotton growth and seed cotton yield of K836, but ⁶⁰Co-γ rays irradiation did not affect Lu Mian 532 and K638. Many plants with morphogenesis changes were found in the M₁ generation population of K836, but few was found in the M₁ generation populations of Lu Mian 532 and K638, suggested that 250 Gy of ⁶⁰Co-γ rays was an appropriate dose for K836 to induce mutant, but the appropriate dose for Lu Mian 532 and K638 should be moderately raised. The M₂ and M₃ seeds of medium mature variety K836 were sowed in automated rain-shelter in Linqing and field in Dunhuang, respectively, for screening drought tolerant mutants. And screened 3 drought tolerant mutants, which established a theoretical foundation in breeding drought tolerant cotton varieties by ⁶⁰Co-γ rays irradiation. (authors)