Abstract
The breeding program of Urochloa ruziziensis evaluates many genotypes in initial phases. Evaluations through grades might make the selection less costly. The aim of this study was to verify the efficiency of visual selection for green biomass yield in relation to different selection strategies, such as mass selection by phenotypic mean, BLUP (Best Linear Unbiased Prediction) and at random. For this purpose, 2,309 regular genotypes were evaluated in an augmented block design in two cuts. The evaluators gave grades for plant vigor, and later, the plots were measured for green biomass yield. The coincidences of the selected genotypes were estimated by different selection strategies. Then, 254 clones of the genotypes selected in different strategies were evaluated in a clonal test in a triple lattice design in four cuts. The statistical analyses were performed in SAS using the Mixed procedure. The regular genotype level and clone-mean basis heritabilities were 31.16 and 62.91%, respectively, for green mass yield. The expected selection gains were 21.09% (visual), 25.43% (phenotypic mean), and 27.5% (BLUP). Moreover, the realized heritabilities for these strategies were 15.58, 11.87, and 15.86%, respectively, which might be associated with genotype by environment interaction. Therefore, the visual selection could be a useful strategy in initial phases of a U. ruziziensis breeding program because the efficiency was moderate to high in relation to phenotypic mean and BLUP.
Highlights
The feed of Brazilian livestock is based on pasture
The aim of this study was to evaluate the efficiency of the visual selection of U. ruziziensis genotypes for green biomass yield in relation to different selection strategies, such as mass selection by phenotypic mean, BLUP (Best Linear Unbiased Prediction) and at random
The regular genotypes consisted of 2,309 genotypes of U. ruziziensis, obtained by seeds, resulting from the second cycle of intraspecific recurrent selection conducted by experiments conducted by Brazilian Agricultural Research Corporation (Embrapa) Dairy Cattle
Summary
The feed of Brazilian livestock is based on pasture. Among the forage species grown in Brazil, Urochloa ruziziensis Brachiaria ruziziensis) has great value for pasture diversification, for milk production (Pessoa-Filho et al, 2015). This species has high nutritional quality when compared with other species of this genus (Lopes et al, 2010) and has shown potential for dry biomass yields that range from 12 to 15 tons/ha (Souza Sobrinho, Lédo, & Kopp, 2011). This species shows adaptability to non-acid and well drained soils, tolerance to aluminum (Bitencourt et al, 2011; Martins et al, 2011), and resistance to spittlebug (Souza Sobrinho, Auad, & Lédo, 2010a)
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