The impact of Teosinte branched1 and reduced height mutations in durum wheat

Abstract

Increasing the yield of wheat requires identifying new genetic combinations of alleles by crossing or by creating variation in yield limiting genes. Wheat yield is impacted by tiller number and seeds per tiller, both of which are impacted by the Reduced height (Rht) and Teosinte branched1 (TB1) genes. In this study, durum plants varying for Rht and TB1 alleles created by EMS mutagenesis were studied to determine the impact of each allele upon agronomic and seed traits. Both projects aimed to increase durum yield, one through an increase in tiller number; the other through the development of a plant with height between current full-height and semi-dwarf varieties that can allocate more resources to seed production. The impact of TB1 null alleles were studied alone and together in greenhouse and field trials, along with an RNA sequencing study to determine the impact of TB1 mutation upon global gene expression in developing meristems. TB1 single and double null mutants produced more biomass and tillers per plant, and expression of genes in meristems varied. A screen of wheat varieties grown in Montana identified that several spring and durum wheat varieties contain different TB1 alleles, but none contained TB1 null alleles. Rht experiments included field trials, coleoptile length and gibberellic acid responsiveness assays, and an in-vitro test to determine the impact of each Rht mutation upon binding to Gibberellin Interacting Domain 1 (GID1) that directly influences plant height. It was found that the previously described Rht-B1b-E529K allele reduced both plant height and coleoptile length while two newly characterized Rht mutations had lesser impacts with trends towards intermediate-height plants. The results of this research demonstrate that Rht alleles that alter RHT binding to GID1 and TB1 null alleles may prove useful in increasing durum tillering and optimizing plant height for different growing conditions.