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

Mason, Richard E.

Committee Member

Pereira, Andy

Second Committee Member

Shi, Ainong

Third Committee Member

Miller, David M.

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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