Characterization of a new temperature-sensitive male sterile line SP2S in rapeseed (Brassica napus L.)

Photoperiod and/or temperature-sensitive male sterility is an economically effective pollination control system for hybrid crops production. This study reports some characteristics of a temperature-sensitive genic male sterile (TGMS) in Brassica napus line, SP2S, which is a spontaneous mutation found in 2007. The fertility alteration in response to temperature was investigated under controlled environment conditions. The pollen abortion was observed under light and electron microscopes to investigate structural and cellular changes associated with male sterility. The results showed that the fertility of SP2S line was greatly influenced by temperature change 12-14 days prior to flowering while photoperiod had no obvious effect on it. The SP2S line became male sterile when daily maximum temperature was above 20 A degrees C and nearly fertile when lower than 15 A degrees C. The size of petal and stamen reduced while the pistil and nectary was normal with good seed set after open-pollination. Microscopic observation in this study revealed the extremely vacuolated and enlarged tapetal cells of PMC during meiosis, which was associated with pollen abortion. The microspores were bonded together and hardly released from tetrads due to the persistence of callose layer covering them. The cytoplasm of degenerated microspores was accompanied by early degraded tapetum. The fertility of SP2S was controlled by at least two recessive nuclear genes and all cultivars could restore the fertility of SP2S. Commercially valuable traits such as seed yield, seed quality, sclerotinia-resistance, lodging, and other agronomical traits of four F-1 hybrids of SP2S were as good as their counterparts from near isogenic line, SP2F. The recessive TGMS genes showed no adverse effect on the performance of F-1 hybrids. Thus, SP2S line is a promising TGMS for hybrid production in rapeseed and canola. This characterization study helped understanding the process of male sterility and producing super hybrids through this two-line pollination control system.