Date of Graduation

12-2020

Document Type

Thesis

Degree Name

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

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Shakiba, Ehsan

Committee Member

Srivastava, Vibha

Second Committee Member

Brye, Kristofor R.

Third Committee Member

Sha, Xueyan

Keywords

QTL Mapping; Restorer Gene; Rice; Seed Length; Seed Thickness; Seed Weight

Abstract

Hybrid rice (Oryza sativa L.) breeding offers a significant opportunity to enhance rice production, and the cultivation of a male sterile line is the most important factor in the success of cross-breeding. One of the key elements of hybrid rice production is to develop a restorer line that is assigned as the male parent. The restorer lines provide viable pollen for fertilization of the male sterile plant due to the presence of a restorer gene (Rf) in their genomes. Any superior restorer line applied to hybrid rice production must contain genes/quantitative trait loci (QTL) associated with the desirable agronomic traits in its genome. The objectives in this study were to 1) identify the genetic source of restorability in two Arkansas-developed restorer lines, 367R and 396R, and 2) identify QTLs associated with seed dimensions in two restorer lines. The study was performed at the University of Arkansas System Division of Agriculture, Rice Research and Extension Center, Stuttgart, Arkansas. Three populations resulting from crosses between 367R and Arkansas advanced lines RU1501139, and 396R crossed with Tropical Japonica cultivar “Newbonnet (PI474580) or Arkansas advanced line RU1501047 were developed. Five F3 plants from each F2:3 line were selected for testcross with an Arkansas developed cytoplasmic male sterile (CMS) line 873A. Five testcross F1 plants resulting from each selected pollen donor plant were grown in the greenhouse. Pollen fertility was tested via a pollen stain procedure (Virmani et al, 1997). The results showed that 367R contains one restorer gene and 396R possesses two restorer genes within their genomes. The genotypic analysis showed that there are two major QTLs, in chromosome (“chr” hereafter) 10, which is co-localized with two previously reported QTLs where Rf4 and Rf5 genes were mapped. For the second part of this study, the parental lines were evaluated for grain length, width, thickness, 100-seed weight, and heading date. The population 367R × RU1501139 (“Population-A”, hereafter) was selected for evaluation of grain length, thickness, and length/width ratio. A total of 300 F3 seeds from F2 plants grown in greenhouse conditions were harvested, cleaned and evaluated using the WinSEEDLE TM image analyzer (Regent Instruments Inc., Canada). A total of 17 QTLs for grain dimensions were identified. Two QTLs in chr. 3 and one each QTL in chr. 7 and 11 were associated with grain length, while two QTLs located in chrs. 3 and 7 were associated with grain length/width ratio. Three QTLs located in chrs. 5, 6, and 8 were associated with grain thickness, while nine grain weight QTLs were identified that included four QTLs in chr. 12, two QTLs in chrs. 1 and 10, and one QTL in chr. 3. These results can be used for developing superior restorer lines and applied to hybrid rice production via marker-assisted selection.

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