Abstract
Common bean (Phaseolus vulgaris L.) originated in medium to high altitude regions and is sensitive to high temperatures. Climate changes from an increase in global temperatures are foreseen, and therefore better understanding of the mechanisms of heat tolerance is necessary. In this context, the aim of this study was to investigate the effects of heat stress on twelve common bean genotypes under natural growing conditions in three locations (Campinas, Votuporanga, and Ribeirão Preto, SP, Brazil) and in two growing seasons (fall-winter 2016 and summer 2016/2017). Data were analyzed by combined analysis of variance in a 2 × 3 × 12 factorial arrangement, considering two crop seasons, three locations, and twelve genotypes as factors. This was followed by the Scott-Knott mean comparison test (P<0.05), genetics, genetics×environment (GGE)-biplot analysis for grain yield and Pearson correlation for the summer season. Significant differences were found for the crop season, location, and genotype for most of the traits evaluated. It was found that the high temperatures, reached in summer, negatively affected the performance of cultivars, resulting in a reduction of 40% in grain yield. Votuporanga, which reached the highest temperatures during the summer, was considered as the most unfavorable environment. The genotypes that proved to be more productive in the summer for the locations of Campinas were BRS Agreste and FT Nobre; for Votuporanga, the genotypes Pérola and IPR Tangará; and for Ribeirão Preto, the genotypes SEA 5 and BRS Estilo. The highlighted correlations observed by the Pearson test were the highest leaf temperature reducing grain yield and, the highest relative index of chlorophyll contributed to higher productivity. Key words: High temperature, Phaseolus vulgaris, selection, genotype × environment interaction, plant breeding.
Highlights
Common bean (Phaseolus vulgaris L.) is one of the main crops produced in Brazil and in the world
The significant effects of the blocks within the location were isolated from analysis for the traits leaf temperature (LT), stomatal conductance (SC), shoot dry matter (SDM), leaf area (LA), and grain yield (GY)
According to Didonet (2010), high temperature may be the environmental factor that has the greatest influence on flower abscission, low setting and final retention of pods, inadequate grain filling, reduction in the number of seeds per pod, and lower seed weight in common bean. This corroborates the results found in these experiments since the production components and grain yield were affected by crop season, showing the differential behavior of the genotypes when exposed to different growing environments
Summary
Common bean (Phaseolus vulgaris L.) is one of the main crops produced in Brazil and in the world. Beans strongly reinforce food and nutrition security among poor consumers, while reducing the risk of cardio-vascular disease and diabetes. It is the most important grain legume for direct human consumption with 23 million hectares grown worldwide, and approximately 12 million metric tons produced annually. Bean crop is grown in a wide range of latitudes with mean air temperature from 14 to 35°C, and due to its origin in medium to high altitude regions, it is sensitive to heat, whereas day and night temperatures above 30 or 20°C, respectively, result in significant yield reduction (Beebe et al, 2011). According to Araújo et al (2015), common bean of Andean gene origin typically adapts better to cooler climate and high altitude (1400-2800 m) regions, whereas genotypes of Mesoamerican origin adapt to higher temperatures in low to medium altitude (400-2000 m) regions
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