ABSTRACT. The objective of this study was to evaluate the performance of 119 full sib progenies of the fifth cycle of reciprocal recurrent selection (RRS) derived from of Universidade Federal de Lavras maize breeding program. The experiment was carried out in an 11 x 11 triple lattice design at two locations (Lavras, Lambari). The plots consisted of two rows of 3 m, with four plants per 1 m and 0.60 meters of spacing between lines. The grain yield was obtained as kg/plot through weighing of husked ears. The contrast between progenies and controls was not significant, indicating there were no significant differences among the average grain yields of the progenies and controls. When considering the joint analysis, heritability was 64.2%; however, this estimate did not differ from the values estimated for each location separately. Estimates of genetic and phenotypic variance among progenies ranged from 0.21 to 0.28 and 0.30 to 0.47, respectively. Estimates of selection gain, for 10% selection intensity, indicated gains of 16% in the joint analysis of the two locations. The progenies of the fifth cycle of RRS had high average grain yield, associated with high variability. In comparison to the average grain yields exhibited by the controls, it was concluded that the progenies have the potential to be commercially exploited.

A alternativa adotada nos programas de melhoramento genético para diminuir o efeito da interação genótipo x ambiente (G x A), é através da avaliação das linhagens em uma rede de experimentos, sendo esses, conduzidos em vários anos e ambientes representativos das regiões edafoclimáticas de cultivo. Diante disso, o objetivo desse trabalho foi avaliar a adaptabilidade e estabilidade produtiva de genótipos de arroz de terras altas no estado de Minas Gerais, utilizando a ferramenta gráfica para análise de dados, o GGE biplot. Foram utilizados dados de produtividade de grãos, provenientes da avaliação de vinte linhagens de arroz do ensaio de Valor de Cultivo e Uso do programa de melhoramento de arroz de terras altas da Universidade Federal de Lavras em parceria com a Embrapa e Epamig. Os ensaios foram conduzidos em delineamento de blocos completos, com três repetições nas safras de 2013/2014, 2014/2015 e 2015/2016. Os experimentos foram conduzidos em um total de nove locais divididos dentro das três safras nas cidades de Lambari, Lavras e Patos de Minas, todas localizadas no estado de Minas Gerais. Concluiu-se com este trabalho que as linhagens foram em quase sua totalidade mais adaptadas e estáveis que as cultivares comerciais. Os genótipos 10 e 13 foram superiores à média geral para produtividade e apresentaram alta estabilidade, sendo candidatos futuros para lançamento como novas cultivares.

The rice crop is affected by diseases throughout its cycle, impacting negatively on grain yield and quality. The control of the disease impact can be accomplished via crop breeding, using highly multiple resistant genotypes. This study aimed to evaluate the efficiency of multiple‐character and specific selection of multiple resistance to major culture‐associated diseases (neck blast, leaf scald and grain discoloration) in rice lines of the Upland Rice Genetic Breeding Program. The experiments were conducted in 35 sites during 12 agricultural years, where 124 lines were evaluated for the severity of fungal diseases, under natural field conditions. Multiple parameters were calculated based on the diseases´ scores: genetic, phenotypic and environmental variances, heritability, selection gain, renewal rate, and genetic and renewal progress. Genetic variance for the disease resistance was identified in the population, and the selection gain for multiple‐character selection was of 3.16 year−1 throughout the breeding process with a renewal rate of over 35%. The programme has showed efficiency in selecting multiple resistant genotypes to the mentioned diseases, highlighting genotypes with high potential for market release.

This study aimed to verify the efficiency of multilines in reducing blast progress and their potential benefits to phenotypic stability in rice. The experiments were conducted in the 2016/17 and 2017/18 agricultural years. A randomized block design was performed with three replications, evaluating 12 lines and a multiline, which consisted of five lines from the Cultivation and Use Value (CUV) test. The multiline presented an estimated grain yield above the average of experiments of around seven bags ha-1 and superior performance in early flowering, justifying the high phenotypic stability for these characters. In this case, the line selection for composing the multiline was favorable and efficient, highlighted by a higher agronomic performance than most lines of the CUV test. The multiline is an adequate strategy to provide higher phenotypic stability and reduce blast progress in the field.

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