Genetic Male Sterility (Ms44) Increases Maize Grain Yield

Abstract

During reproductive development in maize (Zea mays L.), the tassel and the ear compete for available nutrients, at the expense of ear development. The objective of this study was to determine if male sterility (MS) genes could be used to reduce the competition between developing reproductive organs and to improve ear and kernel development. Nitrogen (N) budget experiments conducted in the greenhouse revealed that, under N limiting conditions, the tassel continued to accumulate N prior to anthesis while the ear stopped accumulating N. This finding confirmed prioritization of N partitioning to the tassel at the expense of the developing ear during the critical period of kernel set. Genetic male sterile (GMS) genes were used to terminate pollen production. At anthesis, ear biomass of male sterile plants carrying the ms1 allele increased 92% compared with male fertile plants in a greenhouse experiment. In subsequent field testing, GMS (Ms44 allele) male sterile plants increased grain yield across six N rates between 0 and 170 kg ha−1 (784–2301 kg ha−1), three plant densities between 79,070 and 158,140 plants ha−1 (489–3706 kg ha−1), and in flowering drought stress environments (2768 kg ha−1), compared with male fertile plants. Yield was improved due to increased silk number per ear, kernel number per ear, and reduced barren plants. The dominant GMS allele, Ms44, can be used to produce completely sterile or 50:50 segregating male fertile:male sterile hybrid seed through the use of a transgenic maintainer line. Growing a blend of male sterile and male fertile plants can improve grain yield under a range of growing conditions, including those where drought and N limit crop yield.