Degree Type

Dissertation

Date of Award

2012

Degree Name

Doctor of Philosophy

Department

Agronomy

First Advisor

Walter R Fehr

Abstract

Evaluation of aphid resistant backcross (BC) lines containing the Rag1 or Rag2 alleles alone, or with the two alleles combined, indicated that the mean yields of resistant BC lines were less than the mean of the two entries of their susceptible recurrent parent in each of the three experiments. This reduction in mean yield was significant for BC lines containing Rag1 and its combination with Rag2, but not for BC lines with only Rag2. Among the BC lines in each experiment, only a small percentage were significantly different from the mean yield of their susceptible recurrent parent. Significant differences in mean maturity, height, lodging, protein and oil concentration, and seed weight were observed between BC lines and their recurrent parent, but they were small and not consistent among the three experiments. BC lines within each experiment were identified that did not significantly differ from their susceptible recurrent parent for these traits. These results indicated that recovery of lines with the Rag1 and Rag2 alleles similar to susceptible lines would be possible for the traits evaluated.

A high incidence of Cowpea mild mottle virus-like (CPMMV-L) symptoms occurred in Puerto Rico and Mexico, allowing reliable phenotypic data to be collected. Phenotypic segregation of F2-derived lines satisfactorily fit a 3 susceptible to 1 resistant segregation ratio, and all F1 plants evaluated became infected. Based on the segregation ratio and phenotype of F1 plants, CPMMV-L resistance was controlled by a single recessive allele designated as rbc1. Molecular mapping further confirmed a single gene model by identifying only one significant region on Chromosome 18 (LG G). Location of the locus was narrowed to a 2.4 cM region flanked by SSR markers BARCSOYSSR_18_0456 and BARCSOYSSR_18_0458.

Mean palmitate, stearate, and saturate concentrations of low phytate (LP) F2 plants were significantly higher than that of normal phytate (NP) F2 plants even though all parents used to develop the populations had a saturate concentration <70 g kg-1. Mean saturate concentrations of the lpa1lpa1Lpa2Lpa2 (MW) and Lpa1Lpa1lpa2lpa2 (WM) genotypes were not significantly different from each other, and were both significantly less than that of the lpa1lpa1lpa2lpa2 (MM) genotype. Mean inorganic phosphorus (P) concentration was greatest for the MM genotype, followed by the lpa1lpa1Lpa2lpa2 (MH) and Lpa1lpa1lpa2lpa2 (HM) genotypes. Using parents that both had a saturate concentration <70 g kg-1 to develop the populations resulted in a greater frequency of LP, low saturate (LS) individuals being recovered than what had previously been reported when making crosses with only one of the parents with a saturate concentration <70 g kg-1. The ability to recover LP,LS individuals was attributed to the accumulation of favorable modifying genes for reduced saturate concentration.

Copyright Owner

Ryan Christopher Brace

Language

en

Date Available

2012-10-31

File Format

application/pdf

File Size

144 pages

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