Selection strategies for increasing the yield of high nutritional value leaf mass in Urochloa hybrids

Abstract

Experimental genotype selection in a forage crop cultivar development program is complex because the ultimate aim is increase performance and sustainability in animal production. The objectives of this study were (1) to identify traits with greater direct and indirect effects on yield of high nutritional value leaf mass (NLM) in Urochloa sp. hybrids and (2) to assess indirect gain from selection for these traits with greater effects through selection indexes and by genotype by yield*trait (GYT) biplot analysis using NLM as a basic variable. We evaluated 96 interspecific hybrids, from a gene pool among Urochloa ruziziensis, Urochloa brizantha and Urochloa decumbens species, in an experiment laid out in a randomized complete block design. A series of agronomic and nutritional value traits were measured. Path analysis and GYT were performed using NLM as the basic variable, and different strategies using selection indexes were adopted. The leaf dry matter and field green weight (FGW) traits exhibited greater direct effects on NLM. All selection strategies proved to be effective in obtaining gains in the NLM variable. GYT analysis and the selection index with weights corresponding to the relative direct effects to each trait on the NLM were the strategies that resulted in a greater correlated response for NLM. Indirect selection for NLM via FGW or the index with the FGW and regrowth capacity traits proved to be viable strategies for selection of Urochloa genotypes in the initial stages of the breeding cycles due to their practicality and lower requirement regarding traits to be measured.