Genetic progress of grain quality of flooded-irrigated rice cultivars in the state of Rio Grande do Sul, Brazil

Abstract

The objective of this work was to determine the genetic progress of grain quality attributes of flooded irrigated rice (Oryza sativa) cultivars in the state of Rio Grande do Sul, Brazil, between 1972 and 2016. The genetic estimates followed an approach based on the comparative analysis of 25 cultivars released by Embrapa’s breeding program over this period. The experiment was implemented in four producing regions of the state of Rio Grande do Sul: Sul, Campanha, Planície Costeira Interna, and Planície Costeira Externa. The following significant genetic gains were observed: 0.20% per year, for percentage of whole grains after processing; -1.38% per year, for percentage of chalky kernels and white-core grains; -0.77% per year, for total chalky area; -0.08% per year, for total whiteness; and -0.82% per year, for non-vitreous grain whiteness. Most cultivars released have high amylose content and a low gelatinization temperature. Therefore, the breeding program presented significant annual genetic progresses between 1972 and 2016 for the main attributes of grain quality, and made cultivars available according to the national demand for grain quality in the several segments of the rice production industry.

Predicted genetic gains weighted by selection pressures for grain quality in irrigated rice

“…In the present study, genetic gain, together with the new estimated average, is equal to or higher than the average values obtained by Streck et al (2018) for total chalky area of the commercial cultivars launched by the irrigated rice breeding program of Embrapa Clima Temperado.…”

“…Despite these interesting results, few known studies use this measurement methodology, which allows analyzing quality characters through sample readings with digital technologies considered new; however, its implementation in rice research programs has been gaining space in recent years, together with the interest to increase the grain quality standards in the rice production chain (Sordi et al, 2021). On this topic, some surveys are being carried out in Brazil by Empresa de Pesquisa Agropecuária e Extensão Rural de Santa Catarina (Marschalek et al, 2017(Marschalek et al, , 2020 and Embrapa (Streck et al, 2018), being directly linked to the breeding program or academic research in partnership with graduate programs, as is the case of the present work.…”

Genetic progress of upland rice (Oryza sativa L.) lines for disease resistance

“…Even in the case of CUV assays, which precede the release of cultivars, the presence of variability between lines is very important. It enables the selection of genotypes with different levels of resistance to each disease, aiming to meet the different demands of each region and enables the breeder to select lines according to the objectives of the breeding programme (Cavatte, Silva, & Souza Machado, 2018; Morais Júnior, Melo, De Morais, & Colombari Filho, 2017; Streck, Magalhães Júnior, Aguiar, et al, 2018). Moreover, for multiline constitution, this variability of resistance in the CUV test is very desirable (Santos et al., 2017).…”

“…At the same time, the breeding programme needs to be subjected to critical analysis regarding the possible success in the selection of lines and release of cultivars with disease resistance. In this context, estimating genetic progress is an option for verifying the effectiveness of conducting experiments and evaluations over the years (Ramalho, Abreu, Santos, & Nunes, 2012; Streck, Magalhães Júnior, Aguiar, et al, 2018).…”

Occurrence of rice blast on and grain quality of irrigated rice fertilized with nitrogen and silicates

“…In the Brazilian market, the preference is for grains with a high milling yield of over 70%, without defects and with a high whole grain yield above 60% (Reunião Técnica…, 2018). The characteristics of whole grains, vitreous grains, and chalky kernels, as well as staining defects, are affected by physiological disturbances caused by biotic or abiotic factors and result in the depreciation of the final product (Streck et al, 2018). Therefore, the improvement of grain quality is one of the main selection criteria in breeding programs.…”