RESUMOA produtividade do feijão no Brasil é baixa, mesmo com a existência de cultivares melhoradas com elevado potencial produtivo. Entre os fatores que afetam a produtividade destaca-se a inadequada profundidade de semeadura que proporciona má germinação e emergência, afetando negativamente o estande inicial e final de plantas na lavoura. O presente trabalho objetivou avaliar os efeitos de diferentes profundidades de semeadura sobre a emergência e o desenvolvimento inicial de cultivares de feijão de quatro grupos comerciais. Empregou-se o esquema fatorial 5x4, no delineamento experimental inteiramente casualizado com quatro repetições, sendo 5 profundidades de semeadura (1, 2, 4, 6 e 8 cm) e cultivares de feijão de 4 grupos comerciais (Cavalo, Jalo, Carioca e Preto). Constatou-se que a deposição da semente a 2 cm de profundidade é a mais indicada para os grupos comerciais avaliados e quando superior a 2 cm afeta negativamente a emergência, índice de velocidade de emergência, coeficiente de velocidade de emergência, altura de plântula aos 9 e 21 dias após semeadura, massa verde e seca da parte aérea, massa verde e seca do sistema radicular. Palavras-chave: deposição de semente; estande de plântulas; Phaseolus vulgaris L.; vigor Emergence and early development of bean seedlings at different sowing depths ABSTRACTBean productivity in Brazil is low, even with improved cultivars with high potential yield. The factors affecting productivity include the inappropriate sowing depth that results in poor germination and emergence, adversely affecting the initial and final stand of plants in the field. This study aimed to evaluate the effects of different sowing depths on the emergence and early development of bean cultivars of four trade groups. The factorial design 5x4 was used in the completely randomized experimental design with four replications, five sowing depths (1, 2, 4, 6 and 8 cm) and bean cultivars of four trade groups (Cavalo, Jalo, Carioca and Preto) was used. Seed deposition at 2 cm deep is the most suitable for the evaluated trade groups and deposition deeper than 2 cm adversely affects the emergence, emergence speed index and emergence speed coefficient, seedling height at 9 and 21 days after sowing, green and dry mass of the aerial part, green and dry mass of the root system.
The characteristics of multiple resistance in Euphorbia heterophylla biotypes to herbicides that are inhibitors of ALS (Acetolactate synthase) and PPO (Protoporphyrinogen oxidase) and their responsible mechanisms are still not completely elucidated. The objectives of this study were to identify cross-resistance to herbicides from different chemical groups of ALS inhibitors (imidazolinones, sulfonylureas, pyrimidyl benzoates and sulfonanilides) and also PPO inhibitors (diphenylethers, phthalamides, oxadiazoles, triazolinones and pyrimidinediones) in E. heterophylla biotypes with multiple resistance to these herbicides; to analyze whether the antioxidant enzymes superoxide dismutase (SOD) and peroxidase (POD) constitute mechanisms that are responsible for the resistance to PPO inhibitors. Initially, the response to doses of herbicides from these different chemical groups was determined, using doses below and above the one recommended for the species. The control of E. heterophylla was determined, estimating the required doses for a 50 and 80% control reduction and calculating the resistance factors. The constitutive and induced activities of the SOD and POD enzymes were also determined. The results confirmed cross-resistance for all chemical groups of ALS and PPO inhibitors in the Bom Sucesso do Sul and Vitorino biotypes. The constitutive and induced activities of the SOD and POD enzymes were superior in plants from the E. heterophylla biotypes Vitorino and Bom Sucesso do Sul, contributing to their resistance to PPO inhibiting herbicides.
-Weed resistance to herbicides is a major global problem for agriculture. In recent years, the increased use of herbicides, without proper planning, has led to a large increase in the number of cases of weed biotypes that are resistant to one or more herbicide mechanism of action. Wild poinsettia biotypes (Euphorbia heterophylla), discovered in the State of Paraná, with resistance to herbicides that inhibit protoporphyrinogen oxidase (PROTOX) and acetolactate synthase (ALS), are the first case to exhibit multiple resistance in Brazil. This study analyzed the genetic inheritance of PROTOX inhibiting herbicide resistance in E. heterophylla. Crosses were conducted between biotypes that were susceptible (female parent) and those carrying multiple resistance to ALS and PROTOX inhibitors (male parent) to obtain the F 1 generation. Backcrosses were performed (RC 1 and RC 2 ) and the F 1 generation was advanced to F 2 . F 1 , F 2 , RC 1 , RC 2 generation plants and their parents were subjected to applications of the herbicide fomesafen (250 g i.a. ha -1 ). The observed frequencies in the F 2 generation were not different from the expected frequency of 3:1. All RC 2 individuals were resistant, while the RC 1 population showed a 1:1 segregation, which would be expected when a single gene controls the trait. Thus, it can be inferred that E. heterophylla resistance to PROTOX-inhibiting herbicides is conditioned by a single and dominant nuclear gene.
Euphorbia heterophylla populations endued with resistance to both imazethapyr (an acetolactate synthase inhibitor) and fomesafen (a protoporphyrinogen oxidase inhibitor) were first detected in Brazil in 2004. The objectives of this study were to determine the number and dominance of genes conferring imazethapyr and fomesafen resistance in E. heterophylla and to establish the types of inheritance of the resistance traits. It was hypothesised that two dominant nuclear genes control this herbicide resistance and each gene confers resistance to a single herbicide. We crossed a susceptible (S) and a multiple‐resistant (R) E. heterophylla biotype and generated F1 families which, in turn, were self‐fertilised to produce F2 families. Backcrosses of the F1 families with the S‐ and R parental biotypes resulted in BCs and BCr families respectively. The F1, F2, BCs and BCr families and the S and R parental biotypes were subjected to imazethapyr and fomesafen wherein each herbicide was used as a selecting agent. F1 plants and the S‐ and R parental biotypes were used to evaluate the dominance of the resistance trait in multiple‐dose bioassays with imazethapyr and fomesafen. The observed frequencies of resistant plants in the F1, F2, BCs and BCr families did not significantly differ from the expected frequencies for a resistance trait regulated by two dominant genes in which each gene confers resistance to a single herbicide. The lack of difference in herbicide response between the F1 family and the R parental biotype was taken as evidence for completely dominant resistance to imazethapyr and fomesafen. Herbicide resistance in E. heterophylla presents with dominant monogenic nuclear inheritance for each herbicide mode of action. Our findings underscore the necessity and urgency of adopting integrated strategies to control E. heterophylla and to inhibit the evolution of new herbicide‐resistant strains.
In Brazil, common bean (Phaseolus vulgaris L.) is cultivated in different growing seasons and environments, with different genotypes responses due to the genotype x environment interaction. This study aimed to identify common bean genotypes with a better production stability in each growing environment. The trials were conducted in a randomized block design, with three replications, involving three growing years, nine common bean genotypes and four environments (first and second growing seasons with high and low levels of technological input, such as fertilizers and pest and disease control). Biplot analyses were performed using the GGE Biplot software. The use of high levels of technological input results in an average increase of 14.4 % for yield and is more representative in the crop environments, as well as more adequate for genotype selection. IPR Campos Gerais, BRS Esplendor and BRS Campeiro showed a high stability and presented the best productive performance under both technological levels.
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