Selection of families and parents of sugarcane (Saccharum spp.) through mixed models by joint analysis of two harvests

At present, the sugarcane (Saccharum spp.) breeding programs from around the world have practiced early family selection, because in the early stages of breeding the evaluated characteristics have shown low heritability. This study aimed to select through restricted maximum likelihood/best linear unbiased prediction also known “mixed models” the best families among the 78 that comprise the RB05 sugarcane series, stage T1, of Programa de Melhoramento Genetico da Cana-de-acucar of the Rede Interuniversitaria para o Desenvolvimento do Setor Sucroalcoleiro, Brazil. The experiments, conducted during 2007/2008 and 2008/2009 in Paranavai, PR were implemented using an incomplete-block design with five replicates of each family. Each plot was composed of two planting rows of 5 m, spaced from each other by 1.40 m and spacing between plants was of 0.50 m, containing ten seedlings for planting row, resulting in a total of 20 individuals per replicate of each family. The characteristics evaluated were Brix (°Brix), ton of stalk per hectare (TCH) and ton of °Brix per hectare (TBH). The joint analysis obtained from these three traits in both harvests favored the selection of 35–41 families. The analysis also favored the selection of the best parents. The top five families for Brix were: F41M60, F02M77, F41M82, F61M38 and F62M35; to TCH were F66M30, F35M06, F78M45, F70M30 and F57M46 and for TBH the five elites families were F66M30, F35M06, F78M45, F70M30 and F01M39. The five best sugarcane parents for Brix were RB835486, SP91-1049, SP80-3280, RB72454 and RB925211; to TCH were IAC87-3396, RB941531, RB855511, RB915141 and RB957689, and for TBH the elite were IAC87-3396, RB855511, RB957689, RB941531 and RB855563. As each harvest season had different order of the best families, the joint analysis proved to be a primordial tool for plant breeders.