Date of Graduation

8-2018

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Richard Mason

Committee Member

Andy Pereira

Second Committee Member

Ainong Shi

Third Committee Member

David Miller

Keywords

Grain Yield, Green Revolution Genes, Plant Height, QTL Mapping, Rht Loci, Soft Red Winter Wheat

Abstract

Plant height in wheat (Triticum aestivum L.) is controlled in large part by two major Rht genes, Rht-B1 and Rht-D1, which pleiotropically impact lodging and grain yield. Prior to the Green Revolution, wheat varieties contained only ‘wild-type’ Rht alleles (Rht-B1a and Rht-D1a) and were tall and prone to lodging. Introgression of a semi-dominant mutation at either of these two loci (Rht-B1b or Rht-D1b) results in a semi-dwarf phenotype and reduced plant height. When combined (Rht-B1b and Rht-D1b) an extremely short double-dwarf phenotype is observed. The objective of this study was to determine the impact of allelic variation in Rht-B1 and Rht-D1 on plant height, grain yield, and yield components in soft red winter wheat (SRWW). A doubled haploid population (n = 98) derived from the lines ‘Neuse’ (Rht-D1 dwarfing) and ‘Bess’ (Rht-B1 dwarfing) segregating at the Rht loci, was evaluated in five total site-years in Arkansas. Analysis of variance across locations showed that allelic variation at the Rht loci significantly affected grain yield, plant height, and yield components (p ≤ 0.05) with no Rht x location interaction. Overall, wild-type lines were taller (87.7 cm) and lower yielding (3.38 t ha-1) compared to semi-dwarf lines. Rht-D1 semi-dwarfs had significantly higher grain yield (3.93 t ha-1) and were shorter (81.4 cm), compared to Rht-B1 lines (3.72 t ha-1 and 83.3 cm). Higher grain yield in Rht-D1 semi-dwarf lines was due in part to significantly higher 1000 kernel weight and kernel weight spike-1, which resulted in higher kernel weight per spike. In addition, seven potential QTL associated with most of the traits measured were identified using a bi-parental approach. In conclusion, future breeding work should focus on the development of Rht-D1 semi-dwarf lines adapted to Arkansas environment.

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