Recurrent selection for early flowering and grain yield in upland rice

Abstract

In upland rice breeding programs, in addition to high grain yield lines, obtaining early flowering lines is also important. A good strategy to accumulate favorable alleles and increase gains with selection is the recurrent selection method, which allows obtaining superior lines at each cycle for recombination and lines extraction. The parents choice for the population synthesis is essential for the success of this method, so the aim of this study was to build a base population, called UFLA-P1, and evaluate the progenies of the cycle 0, aiming at beginning a recurrent selection program for the development of early flowering and grain yield upland rice lines. Therefore, F2:4 and F2:5 progenies from the cycle 0 were used, aiming at selecting the best ones and obtaining rice lines within them. For the base population synthesis, hybridizations were carried out between five parents with early flowering and four with high grain yield potential, in partial diallel, which resulted in 19 biparental subpopulations. The F2 population trial was performed in 2017/18 at the Center for Scientific and Technological Development in Agriculture from Federal University of Lavras (UFLA), 15 plants from each population were selected and harvested individually to compose the F2:3 population. The selected genotypes were sown in July 2018 at Embrapa Arroz e Feijão (Brazilian Agricultural Research Corporation) to advance the F2:3 population. The F2:4 population experiments were performed in 2018/19, at the Scientific and Technological Development Center in Agriculture, UFLA and Embrapa Arroz e Feijão. A total of 152 progenies were evaluated, eight progenies from each of the 19 crosses, plus controls, the experimental design used was triple alpha-lattice 12x13, totaling 468 parcels. The genotypes were evaluated and early flowering and grain yield data were subjected to statistical, diallel analysis, principal component analysis and correlation analysis; It was observed that the parents BRSMG Caçula, BRSMG Relâmpago, and BRSMG Caravera showed higher general combining ability (GCA) for the trait and are recommended for obtaining early flowering populations. It was possible to obtain early flowering and high grain yield genotypes in 13 subpopulations. Twenty six genotypes that stood out, from the F2:4 population, were selected to be part of the Observation Trial of the Upland Rice Breeding Program from Federal University of Lavras in the 2019/20, at the Scientific and Technological Development Center in Agriculture at the Scientific and Technological Development Center in Agriculture from Federal University of Lavras. A total of 100 progenies were evaluated, 26 F2:5 progenies, 72 F4:6 progenies from Upland Rice Breeding Program and two controls. Eleven F2:5 progenies from UFLA-P1 Population obtained better performance for early flowering, grain yield and other favorable phenotypic characteristics in rice and were selected to be part of the Preliminary Trial of elite lines. Demonstrating that it was possible to obtain superior lines in the cycle 0 of recurrent selection for early flowering and grain yield in rice. The annual gain obtained with the recurrent selection for days to flowering was -3.48%.