http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Advancements in Sorghum Breeding to Address Emerging Challenges
Developing novel tools to aid in sorghum improvement in an ongoing initiative, and this study aims to addresses two such distinct research objectives. The first objective was to evaluate the effects of the temporal male gametocide trifluoromethanesulfonamide (TFMSA) on treated sorghum inbred lines and their derived hybrids in order to gauge its application within a breeding program. Foliar applications of 25 mg per plant of TFMSA were made to a set of male-fertile B and R lines, and treated plants were compared to the corresponding untreated male-sterile A/ms3-line. Among treated inbreds, there was a delay in flowering, reduction in plant height and an average 15% reduction in hybrid seed production but TFMSA induced near-complete male-sterility and allowed for testcross hybrid seed production across a variety of genotypes. Testcross hybrid comparison did not show any significant difference between TFMSA induced male-sterile lines and the conventional sterility systems such as cytoplasmic- or genetic male-sterility. Results demonstrates that TFMSA can be used to produce breeding crosses, population development or testcross hybrid seed production all of which can aid in breeding objectives. The second objective was to identify quantitative trait loci (QTL) associated with resistance to sorghum aphid (Melanaphis sorghi) in two biparental recombinant inbred (RIL) populations derived from novel resistance source BTx3408. These RILs were genotyped using DArTseqLD and genetic linkage maps of markers were constructed individually for each population in addition to a consensus map. The RILs were phenotyped using a visual scoring scale of 1-9 in representative sorghum growing regions of Texas in experimental sites with ample natural pest populations. Results show that broad sense heritability estimates for the trait ranged between 0.60 to 0.76 and QTL mapping revealed a single major effect QTL on the short arm of chromosome 06 that explained between 22 to 36% of the total variation. Due to limited marker density, the QTL was localized to a genomic region of 1.69 MB. Past studies identified the RMES1 to a 25kb region on chromosome 6 so it is likely that the geen detected herein is the same, but additional studies are needed to confirm this hypothesis. The electronic version of this dissertation is accessible from https://hdl.handle.net/1969.1/198017
Doctor of Philosophy Texas A&M University 2022 https://hdl.handle.net/1969.1/198017