Addition of rye chromosome 4R to wheat increases anther length and pollen grain number

Vy Nguyen, Delphine Fleury, Andy Timmins, Hamid Laga, Matthew Hayden, Diane Mather, Takashi Okada

The research identified rye chromosome 4R arms associated with good pollinator traits, and demonstrated possible use of rye genetic resources to develop elite pollinators for hybrid wheat breeding. Bread wheat (Triticum aestivum) is a predominantly self-pollinating plant which has relatively small-sized anthers and produces a low number of pollen grains. These features limit the suitability of most wheat lines as pollinators for hybrid seed production. One strategy for improving the pollination ability of wheat is to introgress cross-pollination traits from related species. One such species is rye (Secale cereale L.), which has suitable traits such as high anther extrusion, long anthers containing large amounts of pollen and long pollen viability. Therefore, introducing these traits into wheat is of great interest in hybrid wheat breeding. Here, we investigated wheat-rye chromosome addition lines for the effects of rye chromosomes on anther and pollen development in wheat. Using a single nucleotide polymorphism genotyping array, we detected 984 polymorphic markers that showed expected syntenic relationships between wheat and rye. Our results revealed that the addition of rye chromosomes 1R or 2R reduced pollen fertility, while addition of rye chromosome 4R increased anther size by 16 % and pollen grain number by 33 %. The effect on anther length was associated with increases in both cell size and the number of endothecium cells and was attributed to the long arm of chromosome 4R. In contrast, the effect on pollen grain number was attributed to the short arm of chromosome 4R. These results indicate that rye chromosome 4R contains at least two genetic factors associated with increased anther size and pollen grain number that can favourably affect pollination traits in wheat.