Growth and yield component analyses were used to attempt to define the source of grain yield increases (27 to 30% above the cultivar ‘Clintford’) found in oat (Avena sativa L.) lines developed through introgression of Avena sterilis L. germplasm into the Clintford background. Leaf area and leaf area duration were found to be the two traits that could account for the higher yielding ability of the derived lines. By developing a larger leaf‐blade area and delaying senescence, the cultivars had the potential to produce more photosynthate than Clintford. Early development of greater leaf‐blade area probably caused the initiation of a larger number of spikelets per panicle, and the maintenance of a large photosynthetically active system longer after flowering could have caused the development of larger kernels. Higher yield of the derived lines was due to more spikelets per panicle and increased kernel weight. Apparently, the A. sterilis germplasm contributed genes for enhanced leaf growth and delayed senescence which, inserted into the Clintford background, resulted in lines with higher grain yields.

No abstract

No abstract

Mixtures of genotypes are frequently unstable in composition when propagated over successive generations . This study was designed to test whether a multiline cultivar of oats (Avena sativa L .) created to control crown rust disease (caused by Puccinia coronata CDA .) would reflect differential near-isogenic line survivals when propagated under conditions of either presence or absence of rust . An oat multiline cultivar synthesized from near-isogenic lines that had different genes for resistance to crown rust was propagated under rust-free and rust epiphytotic conditions for four successive generations . In the rust-free environment, one near-isogenic line, CI 9192, which was inferior in yielding ability, was reduced significantly from 20% to 10% of the mixture, and CI 9184, which has no yield deviation from normal, increased from 20% to 38% . The other three near-isogenic lines were stable at about 20%. Also, in the rust line of descent, CI 9192 and CI 9184, respectively, decreased and increased significantly .Our results have implications with respect to seed production practices for multiline cultivars; they also raise the question of whether a multiline is stable enough in composition to be called a cultivar .

Vegetative growth index of cereals is defined as the mean quantity of vegetative tissue produced per unit land area per day. Thus, increasing vegetative growth index is a route by which biomass yield can be increased. The proportion of biomass that is translocated to grain is defined as harvest index. In midwestern USA, where harvest index of oats is optimum at ca. 45% and growth duration is restricted to 100-110 days by high temperature, diseases, and drought, breeding for higher vegetative growth index has been proposed as a way to increase grain yield potential for new cultivars.Twelve matings involving Avena sterilis-derived lines and A. sativa cultivars were used to study vegetative growth index. F2-derived lines from these matings were evalutated for vegetative growth index in microplots in field experiments in three environments with four replicates per environment. Vegetative growth index was found to be a quantitatively inherited trait. Heritability values for this trait averaged 54% when the unit of measurement was a microplot. Additive genetic control for vegetative growth index was indicated in seven matings, but in the remaining five, nonadditive gene action was involved in the inheritance patterns. High vegetative growth index segregates were produced more frequently from matings among unrelated parents than from matings of related ones.