Genetic Analysis And Molecular Mapping Of The Thermo-photoperiod Sensitive Genic Male Sterile Genes In Wheat Male Sterile Line 337S (Triticum Aestivum L.)

Male sterility has been identified in more than 600 species, including the most important crops rice, wheat, maize, cotton and rape, and provides a practical way to utilize heterosis for crop production. The discovery of a wild rice cytoplasmic male sterile line resulted in a breakthrough for utilization of heterosis in a self-pollinated crop. The second quantum leap for hybrid rice came from the discovery of a thermo-photoperiod sensitive male sterile line, which significantly simplified the hybrid seed production system and increased the opportunities to screen for strong heterosis combinations. However, breeding for hybrid wheat has encountered much more difficulty than for rice.4Since Kihara obtained the first wheat cytoplasmic male sterile line in 1951, more than 70 wheat genetic male sterile lines such as types T, K, V, D, A, P, CMS have been identified. Utilization of these male sterile lines for hybrid wheat has only achieved limited success. The major limitations included negative alloplasmic and cytoplasmic effects, limited numbers of restoring genes and unstable male sterility.The photoperiod-temperature sensitive genic male sterility resulted from the interaction of genetic factors and environment. The male sterile lines can be partially fertile in some environments, and thus can be self-maintained. This character simplified the hybrid seed production system and reduced the cost of hybrid seed production. Sasakuma and Ohtsuka reported the first wheat long day-length sensitive D² type cytoplasmic male sterile line. Since then, long day-length, long day-length/high-temperature and short day-length/low-temperature sensitive male sterile lines have been identified in wheat. However, most of them are difficult to use for hybrid wheat production due to their requirements for extreme day-length or temperature. In the present study we report a novel thermo-photoperiod sensitive male sterile line, which was sensitive to both short day-length/low temperature and long day-length/high temperature.Utilization of heterosis in wheat has only achieved limited success so far. One or more limiting factors of known wheat male sterile lines prevented them to be widely used for hybrid seed production, which included negative alloplasm and cytoplasm effects, narrow fertility restoring genes or strict requirement to temperature and day-length. The major challenge is still to identify new male sterile gene sources. In the present study, we reported a novel thermo-photoperiod sensitive male sterile line 337S. It is the first wheat male sterile line which is sensitive to both low temperature/short day-length and high temperature/long day-length. This provided two time windows for it to be used as male sterile line for hybrid seed production. The male sterility is controlled by recessive nuclear genes and no cytoplasm effect was observed. All common wheat varieties carry fertility restoring genes for this male sterile line, which provided broad basis to screening hybrid with strong heterosis. Thus, the male sterile line 337S could be widely used for hybrid wheat production.The fertility of a wheat male sterile line 337S was investigated in 4 consecutive years with 18 different sowing dates. Line 337S showed high sterility under both short day-length/low-temperature and long day-length/high-temperature during ear development. It has two time windows to be used as a male sterile line for hybrid seed production. Its fertility rate can be > 50% with suitable sowing time, thus it can be self-maintained as a male sterile line. Line 337S was reciprocally crossed with 7 common wheat varieties and the fertility of their F₁, F₂, BC₁ hybrids were investigated at different...