Agronomic Evaluation of Sorghum Hybrids for Silage Production Cultivated in Semiarid Conditions.

The aim of this study was to study the agronomic traits of different Sorghum bicolor (L.) Moench hybrids for silage productionin semiarid conditions. It was a 1-year evaluation conducted in a randomized block design with 24 treatments and three replicates. The treatments were sorghum hybrids developed by the breeding program of "Embrapa Milho e Sorgo" (Brazilian Agricultural Research Corporation). The fresh matter yield (FMY) in the first cut varied from 22,643.56 to 44,033.15 kg/ha, with an average of 32,607.37 kg/ha, leading to the formation of two groups. Similar results were observed for the dry matter yield (DMY), in which the highest group yielded from 9,471.32 to 14,540.23 kg/ha dry matter (DM). For plant regrowth, there was an increase in the number of stems and a decrease in the amount of panicles. Two groups were formed for the accumulated dry matter yield (ADMY), averaging 14,217.91 kg/ha; the highest group showed mean values of 18,003.00 to 14,221.94 kg/ha. The evaluated sorghum hybrids exhibited satisfactory accumulated forage yields due to their high yield in regrowth, which indicates that they are suitable for use in animal production systems in semi-arid regions.

Resistance of Commercial Hybrids and Lines of Sorghum, Sorghum bicolor (L. ) Moench., to Diatraea saccharalis (Fabr. ) (Lepidoptera: Pyralidae) / Resistência de Híbridos e Linhagens de Sorgo, Sorghum bicolor (L. ) Moench. a Diatraea saccharalis (Fabr. ) (Lepidoptera: Pyralidae)

Híbridos comerciais e uma coleção de linhagens de sorgo da Embrapa, foram avaliados quanto a resistência à broca da cana-de-açúcar, Diatraea saccharalis (Fabr.). Dois experimentos foram instalados no campo em Sete Lagoas, MG, na época da "safrinha", em blocos casualizados, com três repetições e conduzidos sob infestação natural. As plantas foram avaliadas quanto ao estande, ciclo, altura e número de plantas quebradas ou tombadas e produção de grãos. Observou-se também a infestação da broca, o número de galerias, o número total de internódios e o número de internódios danificados para o cálculo do índice de Infestação (II) e índice de Intensidade de Infestação (III). Entre os híbridos comerciais, BR 304 e CMSXS9701 apresentaram os menores II enquanto que Z 732 e Esmeralda destacaram-se com os menores III. Entre as linhagens, 9815017 apresentou o menor II, e 9816003 o menor III. Os dois índices correlacionaram-se positivamente com a altura das plantas nos dois ensaios e negativamente com o ciclo das linhagens. Entretanto, nenhuma correlação foi observada entre eles no ensaio dos híbridos. No ensaio das linhagens verificou-se o ajuste de uma curva logarítmica entre os índices. Embora exista variabilidade genética entre os híbridos comerciais de sorgo para resistência a broca da cana, sob altas infestações, perdas significativas na produtividade poderão ocorrer em todos os híbridos avaliados. Por outro lado, a variabilidade genética observada entre as linhagens de sorgo indicaram um grande potencial para a seleção de cultivares resistentes nos programas de melhoramento.

Commercial sorghum hybrids and Embrapa's lines were evaluated regarding resistance to sugarcane borer. Two field experiments were conducted in Sete Lagoas, MG, under natural infestation, during the second cropping season in a randomized complete block with 3 replicates. The plants were evaluated regarding to stand, maturity cycle, plant height, and number of broken or lodging stalks and yield. The borer incidence, number of galleries, number of healthy and damaged nodes were also evaluated to calculate the Infestation Index and Intensity Infestation Index. Among the commercial sorghum hybrids, Br 304 and CMSXS 9701 were the least infested wile Z 732 and Esmeralda were the least damaged. Among the lines, the least infested was 9815017 and least damaged 9816003. The two indexes were correlated positively with plant height in both experiments and negatively correlated with the lines cycle. However, there was no correlation between the Indexes for the hybrids. Among the lines the data fit to a logarithmic curve. Although there is a significant variability among commercial sorghum hybrids regarding sugarcane borer susceptibility, under high borer density, a significant yield loss can be computed to all hybrids. On the other hand, the genetic variability regarding sugarcane borer resistance among the sorghum lines indicated a significant potential for use in a breeding program of resistant cultivars.