Avanço do programa de melhoramento genético de arroz de terras altas e ganhos para resistência a doenças fúngicas

Abstract

The rice (Oryza sativa L.) is affected by diseases throughout your cycle. They reduce the grains productivity and quality and raise the production cost. The disease impact control can be carried out via breeding, through the use of less susceptible cultivars. This study aimed to evaluate, in relation to biotic stresses, the severity of fungal diseases in upland rice lines, to verify the selection efficiency aim resistance to diseases and to evaluate the lines adaptability and stability of the value for cultivation and use (VCU) belonging to the Breeding Program of Upland Rice of Minas Gerais. The trials were conducted in 35 sites, during 12 agricultural years, in a randomized complete block design with three replicates and plots consisting of 5 rows of 4 meters. A total of 124 lines were evaluated for fungal diseases severity (neck blast, spotting grain and leaf scald) using grading scale proposed by the International Rice Research Institute (1-less than 1% of infected leaf area at 9- more than 50% of the infected leaf area). From the scores assigned to severity, the areas under the disease progress curve were estimated and the data were submitted to analysis of joint variance per agricultural year, with the aid of the statistical program R. Due to the data imbalance, the mixed models approach was also used. There was statistical difference for most sources of variation and variance estimates have evidenced the presence of genetic variability for the characters in question. Based on the gain estimates, the program has been effective in selecting resistant genotypes, even with multi-character selection. The interaction study showed that genotypes G50 and G11 associate good resistance to high adaptability and stability, and Lavras and Lambari environments are discriminant and representative. The Breeding Program of Upland Rice of Minas Gerais has lines with variability for the characters resistant to neck blast, leaf scald and spotting grain, these lines with potential for release.