The objective of this study was to estimate the reduction in yield caused by Colletotrichum graminicola in resistant and susceptible maize hybrids inoculated at different stages of development. Two trials were conducted in different environmental conditions in a randomized block design with treatments arranged as a 2 × 5 factorial scheme and three replications. Treatments consisted of two hybrids (H8664, resistant and H8621, susceptible) inoculated at three growing stages (8-leaf, 12-leaf and tasseling stage). Internal lesion length, adjusted yield, and yield components (length, diameter and ear weight) were evaluated 120 days after emergence. Significant differences in yield and ear weight were detected in the susceptible hybrid inoculated at the earliest stage: yield was reduced by 16.1 and 20.2% in the first and second experiment, respectively. Although lesion length in the susceptible hybrid was approximately three times greater than in the resistant, there were no significant differences in lesion length among treatments for each hybrid. However, there were differences in the number of dead plants and ear weight. It is suggested that damage caused by early infection with C. graminicola results mainly from plant death and reduction in ear weigh rather than from the extent of colonization of the stalk.

As cultivares de aveia-branca (Avena sativa L.) cultivadas no sul do Brasil até princípios da década de 80 eram provenientes do Uruguai e da Argentina, apresentando problemas de adaptação ao ambiente de cultivo. A partir dos anos 70, programas de melhoramento começaram a produzir suas próprias populações segregantes, possibilitando o lançamento em escala comercial de cerca de 35 cultivares. Com o objetivo de estimar o progresso genético nos programas de melhoramento de aveia-branca do sul do Brasil, foi realizado um experimento envolvendo 15 cultivares lançadas em diferentes épocas, em dois locais, com quatro diferentes condições de manejo. Os resultados obtidos indicaram progresso genético linear para os caracteres ciclo vegetativo, rendimento de grãos, peso de grão e peso do hectolitro; a inexistência de efeitos quadráticos significativos sugeriram a possibilidade de ganhos posteriores a partir da seleção de novos genótipos. Os programas de melhoramento genético de aveia-branca do sul do Brasil, embora ainda não tenham atingido o patamar máximo, têm sido eficientes em produzir novas cultivares com maiores rendimento e qualidade de grãos e com caracteres agronômicos superiores.

The oat (Avena sativa L.) cultivars cultivated in Southern Brazil up to the beginning of the 80's were introduced from Uruguay and Argentina. They presented adaptation problems to the new environment. Starting from the 70's, oat breeding programs began to produce their own segregant populations. These programs already released 35 cultivars. Aiming to estimate the genetic progress in oat breeding programs from southern Brazil, an experiment with 15 cultivars released in different times was conducted in two locations using four different cultural practices. The results indicated linear genetic progress for days to flowering, grain yield, grain weight and test weight. The non significance of quadratic effects suggested the possibility of additional gains through selection of new genotypes. The oat breeding programs in southern Brazil have been efficient in producing new cultivars with higher grain yield, good grain quality, and with superior agronomic traits. However, a maximum breeding plateau was not reached for this species.