Association between Genetic Factors for Crown Rust Resistance and Yield in Oats¹

Abstract

SummaryThrough a backcrossing program two series of oat (Avena sativa L.) lines were created, one early and one midseason, that were isogenetic except for genes that conditioned crown‐rust reaction. The lines were tested under crown rust epiphytotic and rust‐free environments, and three of the resistance genes were found associated with sizable deviations in grain yield under the rust‐free conditions. In both early and midseason genetic backgrounds the crown rust reaction gene from C.I. 8079, an Avena sterilis line, was associated with an increase in grain yield. The crown‐rust reaction gene from C.I. 7171 was associated with an increase in yield in the early genotype, but not in the midseason. The crown rust reaction gene from C.I. 7232, a derived tetraploid, was tested only in the midseason genotype in which it was associated with a 9.6% reduction in grain yield.

Characterization in isogenic lines of oat crown rust resistance genes from four sources

“…One possibility of this slight discrepancy might be explained by the fact that, although my mean yields were calculated from 80 sprayed plots, army worms, mentioned below, affected my yield data. However, kernel density correlated with my yield data, and kernel den sity seems to me more efficient than even kernel wt and yield because I was able to draw the same conclusions (except for isoline X5^1) from my kernel density data from one year ex periments as Frey and Browning (1971) did from their three year's yield data.…”

“…In theory, there should be no difference among the yields and components of yield of these Isollnes, However, signifi cant differences do occur, even under rust-free conditions (Table 2; Frey and Browning, 1971). Therefore, yield, kernel wt, and kernel density data were converted to mean ratios of rusted to corresponding nonrusted lines to eliminate Inherent line differences in these characters.…”

“…In Israel, and A. strigosa 'Saia' from South America) proved to have resistance associated with yield genes (Frey and Browning, 1971)• Crown rust resistance genes are easily identifiable; therefore, there is the possibility they can be used as marker genes for yield improvement. For this reason, plant breeders have started to study yield factors in these isolines intensively.…”

GENETICS OF BRASSICA RAPA. 3. COSTS OF DISEASE RESISTANCE TO THREE FUNGAL PATHOGENS

“…Simms (1992) reviews numerous papers on physiological costs of resistance, but genetic studies are rare. Although some data have shown a fitness or yield cost in resistant genotypes, most have involved wide crosses or inbred lines where other loci may be in disequilibrium with resistance genes (Bergelson 1994;Brinkman and Frey 1977;Burdon and Muller 1987;Chaplin 1970;Frey and Browning 1971;Simons 1979). In one highly inbred species, Parker (1991) found nonadaptive evolution of disease resistance attributable to linkage disequilibrium.…”

“…In Escherichia coli, mutations causing resistance to virus T4 carry pleiotropic costs of resistance, which can be ameliorated by epistatic modifiers (Lenski 1988a,b). Several studies from habitually inbreeding species or near-isogenic lines are consistent with the existence of pleiotropic fitness costs (Bergelson 1994;Brinkman and Frey 1977;Burdon and Muller 1987;Chaplin 1970;Frey and Browning 1971;Simons 1979), but linkage disequilibrium and pleiotropy are confounded in these experiments. Additional evidence from ecological and physiological studies are also suggestive of genetic costs of resistance (reviewed in Simms 1992).…”