No abstract

The efficient use of fodder and grassland as the basis of animal feed represents a way of raising productivity and reducing production costs. In this scenario, elephant-grass stands out among the most used forages in the intensive animal production systems in the world mainly due to its high productive potential, support capacity and nutritional quality. The purpose of this work was to estimate genetic parameters for the selection of elephant-grass (Pennisetum purpureum Schumach.) clones for forage production in two seasons, a period of water restriction and the total period of study. We evaluated 80 accessions of elephant-grass by means of the mixed-models methodology (REML/BLUP). The evaluation of DM yield (DMY) of the different genotypes were executed in edaphoclimatic conditions in Campos dos Goytacazes, Rio de Janeiro, Brazil. The Selegen-REML/BLUP software accomplished the statistical and genetic analyses. It was seen that the DMY trait was with a low estimate of coefficient of genotypic variation (3.08%), which demonstrates possible difficulties with the selection for this trait. Heritability-coefficient estimate was 0.3606 for the dry season and 0.4193 for the total period. Those results were the variation in that trait due to genetic causes. Although those values may not be considered of high magnitude, they are of great interest for the breeding mainly because it is a polygenic trait. In both periods, genotypes 7, 25, 41, 43, 57, 58, 62, 64, 68, and 77 stood out among the others, since it presented the highest genetic gains for DMY, which will enhance progress in the evaluated trait.

The elephant grass has gained prominence as one of the main forage species used for biomass production. Therefore, the aim of this study was to identify elephant grass genotypes with high energy biomass production potential by evaluating morpho-agronomic and biomass quality. The following traits were evaluated in this study: dry matter yield (DMY), percentage of whole-plant dry matter (%DM), percentage of neutral detergent fiber (%NDF), percentage of acid detergent fiber (%ADF); percentage of cellulose (%CEL), percentage of lignin (%LIG), percentage of carbon (%C), percentage of nitrogen (%N), and carbon: nitrogen ratio (C: N). Five different production ages were evaluated, and significant differences were observed for the variable DMY. The harvests performed at 20 and 24 weeks of age, provided the best response for biomass energy production (DMY) from elephant grass, averaging 20.50 and 23.77 t.ha −1. The genotypes that most stood out during the evaluation period at the five production ages were King Grass, Mole de Volta Grande, and Mercker 86-México. Genotypes Mole de Volta Grande and King Grass are the most suitable for elephant grass breeding programs aimed at biomass energy production in the conditions of Campos dos Goytacazes-RJ, Brazil.

ABSTRACT. Genetically improved cultivars of elephant grass need to be adapted to different ecosystems with a faster growth speed and lower seasonality of biomass production over the year. This study aimed to use selection indices using mixed models (REML/BLUP) for selecting families and progenies within full-sib families of elephant grass (Pennisetum purpureum) for biomass production. One hundred and twenty full-sib progenies were assessed from 2014 to 2015 in a randomized block design with three replications. During this period, the traits dry matter production, the number of tillers, plant height, stem diameter, and neutral detergent fiber were assessed. Families 3 and 1 were the best classified, being the most indicated for selection effect. Progenies 40, 45, 46, and 49 got the first positions in the three indices assessed in the first cut. The gain for individual 40 was 161.76% using Mulamba and Mock index. The use of selection indices using mixed models is advantageous in elephant grass since they provide high gains with the selection, which are distributed among all the assessed traits in the most appropriate situation to breeding programs.

Studies involving the canonical correlation analysis in forage plants for interspecific hybrids between elephant grass (Pennisetum purpureum) and millet (Pennisetum glaucum) are scarce. The objectives of this study were to obtain estimates of coefficients of phenotypic, genotypic, and residual correlation and evaluate the degree of association between morpho-agronomic and chemical traits in 132 interspecific hybrids between elephant grass and millet. The experiment was conducted in the city of Coronel Pacheco-MG (Brazil). The experimental design was randomized complete blocks with 132 treatments and three replicates. Morphoagronomic and bromatological characteristics were analyzed. The correlation analysis indicated that plants with elevated dry matter yield considering the whole plant, leaf or stem in taller plants and plants with intense tillering have lower crude protein contents, while plants with a greater diameter show lower percentages of fiber and cellulose and greater dry matter digestibility in vitro. By canonical correlations, the chi-squared test at 1% probability by was found that the hybrids showing morpho-agronomic and chemical patterns with taller plants and high dry stem matter yield have increased percentage of cellulose. In contrast, in the same canonical pair, plants with reduced leaf dry matter yield showed lower contents of silica and organic matter and reduced digestibility in vitro. The effect on the improvement of forage quality in hybrids of Pennisetum and millet was evidenced by the better performance of the plants for high dry matter yield of the stem, showing the potential of the same for inclusion in breeding programs.