Evaluation and Utilization of a Chemical Male Gametocide in Sorghum

Abstract

Sorghum bicolor (L.) is an ancient grain and forage crop, grown from the tropics to temperate regions of the world. It is a self-pollinated species that can be grown as either a pure line cultivar or hybrid, depending on the region of production. Existing methods of hybridization of sorghum are useful but have some limitations. Methods of inducing temporal male sterility could enhance several aspects of sorghum breeding. One potential application of temporal male sterility would be to scale up cross-pollination in order to implement a doubled haploid (DH) breeding system in sorghum. A chemical male gametocide that reliably renders plants male-sterile might be ideal for this purpose. Two studies were conducted to assess the utility of trifluoromethanesulfonamide (TFMSA) as a chemical gametocide of sorghum. The first study evaluated the amino acid composition of anther and glume tissues following application of TFMSA. To do so, anther and glume tissue were excised from florets of plants that had received an application of either 0 mg, 2 mg, 6 mg, or 20 mg. TFMSA. After excision of the tissues, the amino acids were extracted in Milli-Q® water; then -high-pressure liquid chromatography (HPLC) was used to quantify the amino acids. Fold changes were calculated to look for shifts among treated and untreated plant tissues. In the anther tissues, several amino acids experienced drastic shifts, the most notable being a >10x decrease of proline and a >20x increase of asparagine. Similar shifts were not observed in glume tissue. Consequently, one, or, both of these shifts may be associated with the induction of male sterility. The second study was conducted to evaluate the efficacy of TFMSA to induce male sterility in two field environments. Both environments were grown in College Station with planting dates that differed by 2 weeks. TFMSA was applied to three distinct genotypes using both hand application and backpack sprayer application in dosages ranging from 5 mg to 30 mg Multiple applications of the 10 mg and 15 mg dosages were also evaluated. Results indicated that once a minimum dosage threshold was exceeded, specific dosages and number of applications had little overall effect on male sterility. Use of a backpack sprayer showed sterility induction albeit at slightly lower levels of male sterility. The results indicate that TFMSA can be used as an effective and durable chemical male gametocide in sorghum