No abstract

RESUMO O déficit hídrico durante o desenvolvimento do amendoinzeiro prejudica vários processos fisiológicos da planta e reduz sua produtividade. Este estudo objetivou avaliar o rendimento de grãos, componentes de produção e crescimento de cultivares e linhagens de amendoim submetidas a déficit hídrico, em condições de campo. O delineamento experimental foi o de blocos ao acaso, com parcelas subdivididas e três repetições. Os tratamentos de déficit hídrico (com e sem) constituíram as parcelas e os genótipos avaliados (IAC Tatu ST, BR1, BRS Havana, Col 72 e Col 82) as subparcelas. A irrigação foi suspensa nas parcelas submetidas à deficiência hídrica entre 35 e 75 dias após a emergência. O crescimento das plantas, massa seca da parte aérea e área foliar foram afetados negativamente pelo déficit hídrico. Verificou-se incremento da diferença entre as parcelas com e sem deficiência hídrica, conforme o aumento do período de supressão de água. A cultivar BRS Havana e a linhagem Col 82 apresentaram tolerância moderada à seca, com os maiores rendimentos de grãos em condição de déficit hídrico. O déficit hídrico foi responsável por redução de 68 % no rendimento de grãos na cultivar IAC Tatu ST, 44 % no número de vagens por planta na linhagem Col 82, 11 % no número de sementes por vagem na linhagem Col 72 e 11 % na massa de 100 sementes na cultivar BRS1.

Water stress is one of the main limiting factors for common bean crops, negatively affecting grain yield and seed quality. Thus, the objective of this study was to evaluate the inheritance of agromorphological and physiological traits related to drought tolerance in order to identify promising combinations. The experiment was carried out in a greenhouse with a partial diallel scheme between three drought-tolerant genotypes (IAPAR 81, BAT 477. and SEA 5), and nine cultivars widely grown in Brazil (BRS Estilo, IAC Alvorada, IPR Campos Gerais, IPR Uirapuru, IPR Nhambu, BRS Esteio, IPR Garça, BRS Radiante, and DRK 18), in a randomized block design with four replicates. The plants were grown in pots with substrate under 80% of pot capacity until they reached the stage R5, when water supply was restricted to 30% for 20 days in the pots under stress treatment. A wide variability for the agromorphological and physiological traits was observed. Water deficit reduced plant performance for most agromorphological traits and altered their physiological metabolism. Additive and non-additive effects are involved in the genetic control of the majority of agromorphological and physiological traits both under water stress and control (well-watered) conditions. The parental genotypes BAT 477 (group I) and IAC Alvorada, IPR Uirapuru, and BRS Esteio (group II) may be included in breeding programs aiming at improving drought tolerance in common bean since they present high positive general combining abilities for agromorphological traits. The crosses IAPAR 81 × IPR Campos Gerais, and SEA 5 × BRS Radiante resulted in the best combinations considering grain yield per plant and total dry biomass, when cultivated under water deficit.

Water deficit is one of the main factors that reduce grain yield. A better understanding of the mechanisms related to this abiotic stress is a key aspect to design and act upon drought tolerance improvement in crop plants. Therefore, the major objective of this study was to investigate four common bean genotypes for drought tolerance and to establish their tolerance mechanisms. The experiment was carried out in a greenhouse, using the completely randomized design in a factorial arrangement (2 9 4), composed by 2 water conditions (well-watered and water deficit) and 4 cultivars, with six replicates per treatment. The four cultivars, two drought-sensitive (IAC Tybatã and BRS Pontal) and two drought-tolerant (IAPAR 81 and BAT 477), were evaluated for some physiological, biochemical and morphoagronomic traits. Drought promoted physiological and metabolic changes in the plants, reflecting on the morphoagronomic traits. Under water deficit, the genotype IAPAR 81 stood out from the others in terms of physiological characters, however, it presented a low efficiency concerning biochemical activities and a significant reduction in the morphoagronomic characters. The cultivar BAT 477 demonstrated to be drought-adapted presenting more efficient biochemical and morphoagronomic adaptions and the genotype BRS Pontal obtained morphoagronomic values similar to BAT 477, thus it may be classified as moderately tolerant to drought.

Although common bean plants can fix atmospheric nitrogen (N2), this process is insufficient to meet the total nitrogen (N) demand of the crop. Thus, the objective of the present study was to compare different N‐responses indices of common bean cultivars in contrasting N fertilization environments. In addition, the genetic variability of the cultivars was verified using SNP and AFLP markers. Cultivars that showed high tolerance to low‐N (LNTI) generally had low N‐agronomic efficiency (NAE), confirming the complexity of simultaneously selecting for genotypes that show both traits. The performance under contrasting N (PCN) index presented the highest heritability and selective accuracy estimates, suggesting PCN may be the most appropriate index to select genotypes. The cultivars were grouped into four groups using molecular markers. Based on the PCN index, cultivars assigned to molecular groups 1 (‘IAC Sintonia’, ‘IPR Bem‐te‐vi’, ‘BRS Notável’, ‘IPR Juriti’, and ‘BRSMG Pioneiro’) and 2 (‘IPR Sabiá’, ‘IPR Quero‐Quero’, and ‘IPR Campos Gerais’) were recommend for future crosses aiming at developing cultivars less dependent on N fertilizers.