Using additive indices and principal components to select sexual genitors and hybrids of Urochloa decumbens

Filipe Inácio Matias,Gustavo Vitti Moro,Beatriz Tomé Gouveia,Cacilda Borges Do Valle,Sanzio Carvalho Lima Barrios

doi:10.1590/1984-70332020v20n2a18

Abstract

Abstract The selection of sexual genitors in Urochloa decumbens breeding is dependent upon the performance of their progeny simultaneously for several traits. Thus, our objectives were to (i) compare the efficiency of indices to select genitors of U. decumbens, (ii) evaluate the genetic gains obtained through selection intensities, and (iii) evaluate the multivariate pattern of progenies through principal components analysis (PCA). For this purpose, 1415 hybrids from 75 progenies of full siblings were evaluated at Embrapa Beef Cattle (Brazil) using seven cuts for dry matter production, regrowth, protein, fiber, lignin, and percentage digestibility. Statistical analyses were performed using mixed models and PCA. The direct selection for dry matter production provided a 37.51% genetic gain. Agronomic traits using indices provided greater gains. Genitors selected using PCA Biplot were similar to selections using indices. Indices and PCA were proven to be an excellent tool to select multi-traits in U. decumbens.

Highlights

Urochloa decumbens is a perennial savanna grass native to Africa and widely grown in pastures to feed cattle on tropical livestock farms (Euclides et al 2016)
Our objectives were to: i) evaluate 1415 hybrids from the first cycle of “a recurrent selection program based on specific combining ability” with 75 full sib families of U. decumbens; ii) compare the efficiency of different selection indices to select superior sexual genitors for total dry matter, regrowth capacity, crude protein, digestibility, fiber, and lignin; iii) evaluate the genetic gains obtained with different selection intensities; and iv) evaluate the multivariate pattern of progenies through principal components analysis (PCA)
This population is part of the Embrapa Beef Cattle germplasm bank located at Campo Grande (MS/ Brazil) and represents the first cycle of a recurrent selection program based on specific combining ability

Summary

Introduction

Urochloa decumbens is a perennial savanna grass native to Africa and widely grown in pastures to feed cattle on tropical livestock farms (Euclides et al 2016). The success of this species is because of its high biomass production in warm and dry environments, regrowth capacity, and tolerance to acidic soils (Jank et al 2014). Despite the importance of this species to tropical regions, there is only one cultivar registered in the Brazilian National Register of Cultivars (RNC 2020), U. decumbens Basilisk (Jank et al 2014) It is a segmental allotetraploid and aposporous apomictic (Worthington et al 2016). In 2009, a sexual diploid accession of U. decumbens was artificially tetraploidized using colchicine (Simioni and Valle 2009) providing the possibility to start intraspecific hybridization with the apomictic U. decumbens Basilisk as the pollen donor

Objectives

Methods

Results