Genetic progress during 22 years of improvement of carioca-type common bean in Brazil

Abstract

Between 1984 and 2010, the program for the improvement of common bean coordinated by Embrapa Rice & Beans released 50 new cultivars at an average rate of 1.9 cultivars per year. Any breeding program must be periodically subjected to critical analysis with respect to its performance, seeking methodologies that can improve its effectiveness. In this context, the estimation of genetic progress is one of the options used in this analysis. The aim of the present study was to estimate the genetic progress in terms of grain yield and other agronomic traits achieved by the Embrapa program. These estimates represent the progress achieved during a 22-year period between 1985 and 2006 and totaling 11 biannual cycles of final assessments of the lines. Two types of field experiments were performed to assess the genetic progress: field experiments of lines and of cultivars. To perform the line experiments, the top three inbred lines from each of the 11 cycles evaluated comprised the 33 evaluated treatments. These evaluations were established in 20 environments and served to estimate the progress in yield, quality, and size of grains because these were the criteria applied to select the elite lines. The cultivar evaluations included the 10 cultivars recommended by the Brazilian Agricultural Research Corporation (Empresa Brasileira de Pesquisa Agropecuária – Embrapa) during the investigated period and were established in 21 environments. These evaluations served to estimate the improvements in the reaction to angular leaf spot, plant architecture, and resistance to lodging because cultivars usually exhibit superior phenotypes for such characteristics. The experimental design in all evaluations included completely randomized blocks with four replicates. The evaluations were performed during three sowing seasons (rainy, dry, and fall-winter) between 2008 and 2010. The results show the efficiency of the Embrapa program in improving the genetic makeup of common bean in Brazil between 1985 and 2006. The estimated improvement in grain yield was 17.3kgha−1 or 0.72% per year. Improvements were also found in plant architecture (2.0%), tolerance to lodging (2.0%), and grain quality (2.4%). There was no significant progress for the character weight of the 100 grains or for resistance to bacterial blight.