Wheat (Triticum aestivum L.) is one of the most important crops in the world. Brazil is one of the largest importers of this cereal, and wheat breeding programs are attempting to increase productivity and reduce external dependence. The objectives of this study were to quantify the spring wheat genetic gain in Brazil between 1984 and 2014 using data from multienvironment trials, and to verify if the genetic gain stagnated after the 2000s. This study used a highly unbalanced dataset containing grain yield (GY) data from 187 spring wheat trials that were performed at 25 locations between 2002 and 2015. In total, 126 cultivars, released between 1985 and 2014, were evaluated over 14 crop seasons. The cultivar evaluation indicated that there was a genetic gain in GY of 33.9 kg ha−1 yr−1 (r2 = 0.53, P < 0.01), which represents an increase of 1.28% yr−1. The dataset showed a linear regression for the genetic gain and indicates that wheat genetic gain has not stagnated in Brazil after the 2000s.
O plantio direto abrange grandes áreas cultivadas no Brasil, sendo considerado adequado para a sustentabilidade dos agroecossistemas brasileiros. O objetivo deste trabalho foi avaliar os efeitos de diferentes sistemas de manejo do solo e de rotação de culturas sobre os atributos físicos e químicos do solo, como também sobre a produtividade da soja. O experimento foi conduzido por quatro anos (2014-2017) na área experimental do Departamento de Diagnóstico e Pesquisa Agropecuária (DDPA) / Secretaria da Agricultura, Pecuária e Desenvolvimento Rural (SEAPDR), Vacaria, RS. O delineamento experimental utilizado foi inteiramente casualizado, com quatro tratamentos e seis repetições. Os tratamentos consistiram em: plantio direto com sucessão de culturas (PDs), plantio direto com rotação de culturas (PDr), escarificado com rotação de culturas (Er) e preparo convencional com rotação de culturas (PCr). Foram avaliadas características químicas (MO, P, K e pH) e físicas (densidade, macroporosidade e microporosidade) do solo e a produtividade da cultura da soja. Após quatro anos de condução do experimento, os atributos químicos do solo não sofreram modificações pelos manejos adotados, porém houve um aumento dos teores de matéria orgânica em todos os tratamentos avaliados. Para as variáveis físicas macro e microporosidade do solo não houve diferença significativa entre os tratamentos, mas a densidade do solo mostrou-se sensível para a mudança no preparo do solo. A produtividade não apresentou diferença entre os tratamentos. Os resultados preliminares mostram que a curto prazo não há necessidade de manejar o solo a cada três anos em áreas que utilizam a técnica do plantio direto.
The objective of this study was to analize the inheritance of characters in wheat using multivariate analysis of variance. Sixteen genetic constitutions were evaluated between commercial cultivars and progenies F1 and F2. Treatments were arranged in completely randomized blocks, with three replicates. Five characters were evaluated. Multivariate analysis of variance and multivariate contrasts were then performed to test the hypotheses. The significant differences, obtained for comparison between parents and progenies F1, may be evidence of heterosis occurrence. However, only comparisons between progenies P1_P3 (F1) vs. P1_P3 (F2) and P4_P2 (F1) vs. P4_P2 (F2) showed significant differences. Multivariate analysis of variance revealed that inheritance of the characters studied is predominantly of the additive type. It is possible that, this occurred due to the degree of relationship between parents who reunited identical alleles at the same locus, by ancestry, as a result of inbreeding effects. The knowledge of additive inheritance may represent a faster incorporation of resistance or quality characteristics in new cultivars.
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