Effectiveness of Recurrent Selection in Irrigated Rice Breeding

Abstract

Plant breeding for quantitative traits is a complicated task; thus, the recurrent selection method has been used in the rice (Oryza sativa L.) breeding program at the Brazilian Agricultural Research Corporation (Embrapa). Our general objective was to assess the effectiveness of this method in achieving genetic progress, maintaining genetic variability, and increasing the potential for selection of superior lines. A genetically broad‐based population of irrigated rice, CNA12S, submitted to three selection cycles was used in this study. The dataset comprised 10 yield trials, in which 667 S1:3 progenies and six check cultivars were assessed for grain yield, plant height, and days to flowering. We measured effective population size in each cycle, using standard and linkage disequilibrium methods, and Nei's genetic diversity in the third cycle. Such analyses were performed using data of single‐nucleotide polymorphism markers from progenies of the third cycle. For estimating the genetic gain, we adapted a generalized linear regression method to the Bayesian approach. This approach was also used to estimate variance and covariance components, according to the multivariate linear mixed model. Magnitudes of genetic and relative variation coefficients, as well as Nei's genetic diversity, indicated maintenance of genetic variability over cycles. Mean genetic gain per year was 1.98% for grain yield and −1.29% for days to flowering. Genetic potential of the population for extraction of superior lines was increased, considering single‐, two‐, or three‐trait selection. Our results show the effectiveness of the recurrent selection method when applied in rice breeding, although some refinements in the selection strategy could further improve its efficiency.

Assessing Prediction Models for Different Traits in a Rice Population Derived from a Recurrent Selection Program

“…Details of the genealogy, developmental steps, and subpopulations composing CNA12S are described in Morais Júnior et al (2017a). Couch).…”

“…Couch). Details of the genealogy, developmental steps, and subpopulations composing CNA12S are described in Morais Júnior et al (2017a). In this study, we evaluated 196 S 1:3 progenies from the third selection cycle of this population.…”

“…Breeding methods commonly used in self-pollinated species have limited potential for improving quantitative traits and combining favorable alleles coming from many different parents (Bernardo, 2010;Ramalho et al, 2012). Recurrent selection may be a flexible tool for the continuous improvement of genetically diverse populations, increasing the frequency of favorable alleles while maintaining useful genetic variability for long-term gains (Ramalho et al, 2005;Hallauer et al, 2010;Niu et al, 2010;Morais Júnior et al, 2015, 2017aLeite et al, 2016). Initially, the frequent crosses required for progeny recombination limited its application in rice.…”

Genetic progress over twenty-three years of irrigated rice breeding in southeastern Brazil

“…For example, low yield has been achieved for irrigated and upland rice (Peng & Khushg, 2003;Tabien et al, 2008;Breseghello et al, 2011;Pieters, Graterol, Reyes, Álvarez, & González, 2011;Yuan, 2017). However, given the increasing limitation of the world's arable land for rice cultivation and the impacts of climate change, the genetic gains achieved are less than those that are required to supply the international market and maintain affordable prices for consumers (Morais Júnior et al, 2017).…”

Research Article Performance of a breeding program for irrigated rice in Southeast Brazil

“…As a result of this partnership, 31 rice cultivars were made available in Minas Gerais, of which 18 are suitable for irrigated crops in floodplains and 13 for rainfed conditions. The strategy for this success is to obtain, gradually, genetic gains while preserving the genetic variability for continuous improvement of yield, grain quality, resistance to diseases and other agronomic traits (Breseghello et al, 2011;Colombari Filho et al, 2013;Martínez et al, 2014;Morais Júnior et al, 2017;Barros et al, 2018). Another important impact of the program is the high rate of adoption of new rice cultivars by farmers, which in itself demonstrates the efficiency of the breeding program (Soares et al, 1999).…”