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

Factors influencing survival among four competing races of Puccinia coronata avenae

“…The sparse infection by races 216 and 264A after 4.5 hr in the moist chamber and 70-80% relative humidity in the greenhouse pointed out the slower rate of germination and appressorium for mation by these races compared to that of races 264B and 326. These results should be correlated with that for appressorium formation found by Singh (1971) where race 326 produced the most appressoria followed by races 264B, 216, and 290. Thus, races 2643 and 326 have a competitive advantage during the penetration process; however, races 264A and 264B were more competitive when low relative humidity was a limiting factor during the penetration and post-penetration process.…”

“…spore yield was greater on Clinton than on Cherokee or Markton. Singh (1971) concluded that the uredia of 2» coronata race 326 were longer than those of race 290 ten days after inoculation.…”

Studies on the association between grain yield and crown-rust reaction loci in several genetic backgrounds of Avena sativa

“…In the case of my study, microplot experiments were used be-cause, for many useful oat lines (i.e., they were either homozygous resistant'or susceptible), there were not enough seeds to sow an experiment with four-row plots. There are at least two possible explanations for the four-row plots being more definitive than the microplots : (1) the sample size of plants used for estimating grain yield in a microplot was 30, whereas in four-row plots the harvested sample was 500 plants (only 2.5 m of each of the two center rows were harvested), and (Singh, 1971) and, therefore, different sets of re sistance genes could have been transferred to the isolines X5^1 and X447. This may explain why a grain yield increase was associated with the resistance allele in X5^1 and not in…”

“…Falconer (1964), quoting Bartlett and Haldane (1935) When it was originally assumed that a pair of isolines (i.e., an early and a midseason) with crown-rust resistance from the same donor carried the same resistance allele, the presence of an associated yield deviation in one isoline but not in the other was assumed to indicate either (a) the yield allele showing epistatic gene action or (b) the previous occurrence of a crossover between the rust reaction and yield loci. However, when Singh (1971) showed that the two isolines derived from one source sometimes carried rust-resistance genes at different loci, neither of these explanations was necessary to explain the results Prey and reported. My experimental results, of course, tend to argue that certain of the yield alleles from the isolines do show epistatic gene action, since certain grain yield associations were trans ferred consistently into the three recurrent genetic back grounds, while other yield associations were not.…”

Studies on the association between grain yield and crown-rust reaction loci in several genetic backgrounds of Avena sativa

“…Singh (1971) later found resistance to crown rust races 264B, 290, and 326 carried by X469II broke down under high tempera- …”