Development of thermo-sensitive cytoplasmic male sterile (TCMS) lines of wheat characterized by complete male sterility at lower-temperatures and partially restored fertility at higher-temperatures

A ''two-line hybrid system'' was developed using thermo-sensitive cytoplasmic male sterility (TCMS) from Aegilops kotschyi and is proposed as a means for seed multiplication and production of hybrid wheat. The TCMS line is crossed to a pollinator line during the normal wheat-growing season for production of hybrid wheat seeds, whereas the TCMS line is maintained through self-pollination in an environment with high temperatures. The male sterile wheat line KTP3314A, containing Ae. kotschyi cytoplasm and the short arm of chromosome 1B from Triticum spelta, was studied in different temperature regimes. KTP3314A was completely male sterile under normal wheat growing temperatures (< 18 A degrees C). Sterility of KTP3314A was partially restored when plants were grown at temperatures above 20 A degrees C during growth stages 45-52. Male fertility was not correlated with day-length. A series of TCMS lines derived from KTP3314A showed similar environmental responses and performed well in hybrid wheat production at lower temperatures. Fertility of these TCMS lines at higher temperatures makes it possible to produce large quantities of male sterile parental seeds. Based on these findings, application of the TCMS-dependent two-line system in hybrid wheat breeding appears to have a promising future for hybrid wheat production.