Heterosis between a male-sterile line and the normal male-fertile materials in flax^*

Jianping Zhang^1,2, Zhanhai Dang^1,2

Abstract: Heterosis in flax (Linum usitatissimum L.) was determined for seed yield, yield components, fiber length, and oil content by the cross between a thermo-sensitive male-sterile line and 51 normal cultivars. F₁ plants showed strong positive heterosis in seed yield, ranging from 4.60 to 1504% depending on the cross combinations. An average of 66% heterosis in seed yield was observed in F₁ when the cultivars currently used in commercial production in China were used as the male parents. In F₂ generation, the heterosis in seed yield was still strong (13.4% for the currently used cultivars) but much lower than that in F₁. The heterosis in the yield components was generally positive and the magnitude was in the following order: yield per plant > bolls per plant > 1000-seed weight > seeds per boll. Most cross combinations had negative heterosis in fiber length and positive heterosis in oil content. This research was unique in that a male-sterile line was used as the female parent in determining the heterosis. These results suggest that use of hybrids can significantly increase the seed yield and that this male sterility is capable of producing hybrids that may have significantly higher seed yield than the current cultivars.