Introgressing photoperiod/thermo-sensitive genic male sterile gene into Basmati 370 rice

Abstract

The emasculation of male gametes in pollen-recipient parents among self-pollinated crops (rice) is key to producing quality hybrid rice seeds. One of the emasculation tools in rice breeding is the photoperiod-thermo sensitive genic male sterility (P/TGMS) method, which ultimately requires long daylight length and high-temperature growth conditions to induce male gametes sterility. Using the P/TGMS method to produce hybrid Basmati rice seeds has been slow because no commercial line has been developed. Crossing the Basmati rice line with a non-aromatic rice line produces F1 with non-basmati quality traits. This study aimed to introgress the p/tgms12-1 gene into Basmati 370 by treating P/TGMS lines (IR-7327-2376-157S and IR-75589-31-27833S) with daytime temperatures (>33ºC) under a polythene greenhouse to emasculate pollen and cross-pollinating them with Basmati 370. Marker-assisted backcrossing was used to develop the BC1F2 Basmati breeding lines evaluated for pollen sterility and agro-morphological traits. Pollen sterility was tested by staining with 1% iodine potassium-iodide solution (I2KI), in which fertile and sterile pollen grains were stained with blue-black and yellow-pink dyes, respectively. The acquisition of near-complete pollen sterility among female parents is a manifestation of the greenhouse temperatures effectively emasculating pollen in P/TGMS parents and BC1F2. Analysis of variance on agro-morphological data showed significantly better agro-morphological traits in BC1F2 than the parents and significantly higher pollen sterility in P/TGMS lines than Basmati 370 (P≤0.05). The presence of the fgr gene in BC1F2 lines was confirmed using SSR markers, and the hybrids had both homozygous aromatic and heterozygous non-aromatic traits, the successful development of BC1F2 with p/tgms12-1 and fgr genes. The results obtained from this study are a major milestone towards improving Basmati rice yields in Kenya using hybrid seeds.