Genetic analysis of seed dormancy in wild oat (Avena fatua)

Steven Alan Fennimore, Purdue University

Abstract

Wild oat persists as a major weed of cereals and other crops due to seed dormancy. Dormancy, which allows seeds in a population to germinate over long periods of time, is a trait that enhances the probability that some individuals will encounter favorable conditions and reproduce. Previous work indicates that seed dormancy in wild oat is a quantitative trait controlled by three or more genes; however, the genetic and molecular mechanisms of seed dormancy are not understood. To investigate the genetics of seed dormancy in wild oat, inbred dormant (M73), and nondormant (SH430) lines were cross pollinated to produce F$\sb1,$ F$\sb2,$ F$\sb3,$ F$\sb7$ recombinant inbred lines, and reciprocal backcrosses. The germination phenotypes of F$\sb1,$ F$\sb2,$ F$\sb3,$ and backcross populations were determined at 15 and 20$\sp\circ$C, as well as in progressively higher concentrations of gibberellic acid (GA). F$\sb1$ populations were also classified at 10 and 25$\sp\circ$C, and the F$\sb7$ recombinant inbred lines were classified at 15$\sp\circ$C. Early germination was dominant at 10 to 15$\sp\circ$C, but at imbibition temperatures of 20 to 25$\sp\circ$C, later germination was partially dominant, i.e., there was a genotype by germination temperature interaction. A three gene model was proposed: genes G$\sb1$ and G$\sb2$ promote early germination, and the D gene promotes later germination. If at least two copies of the dominant alleles of either G$\sb1$ or G$\sb2$ are present, early germination is dominant at 15$\sp\circ$C, but dominance shifts to D at imbibition temperatures of 20$\sp\circ$C and later germination results. Gibberellic acid was found to be principally involved in germination rather than regulation of seed dormancy. The family heritability of seed dormancy was estimated at $\rm h\sp2\sb{f,\ F{=}1}=0.75.\ F\sb2$ bulks, one with high levels of seed dormancy, and one with low levels of seed dormancy, were screened with 800 random decamer primers, i.e., RAPD analysis. Two RAPD markers, OPT-04 and OPX-06 were found to be associated with early germination, accounting for 7 and 13 percent, respectively, of the phenotypic value, i.e., days to germination. Marker OPF-17 was associated with later germination.

Degree

Ph.D.

Advisors

Foley, Purdue University.

Subject Area

Botany|Genetics|Molecular biology

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