Carlos Alberto Gonsiorkiewicz Rigon

Dissimilaridade genética e análise de trilha de cultivares de soja avaliada por meio de descritores quantitativos

Alem das avaliacoes entre genotipos, a utilizacao de tecnicas multivariadas possibilita restringirem-se os erros, principalmente quanto a diversidade genetica, podendo-se, assim, prever combinacoes com maior efeito heterotico, alem da maior possibilidade de recuperacao dos genotipos superiores. Objetivou-se, com este trabalho, avaliar a divergencia genetica entre 18 cultivares de soja, por meio de seis caracteres morfoagronomicos. Foi realizada a analise de trilha, para averiguar as contribuicoes direta e indireta desses caracteres sobre o rendimento de graos. A distância generalizada de Mahalanobis fundamentou as tecnicas de agrupamentos, tanto a de Tocher, bem como a do dendrograma por ligacao simples. Observaram-se cinco grupos divergentes, sendo nove genotipos considerados similares entre si, enquanto os cultivares CEP 59, Netuno e Urano foram formadores de grupos isolados pelos dois metodos de agrupamento. Quanto a analise de trilha, observou-se que os caracteres indiretos pouco influenciaram o rendimento de graos, tendo relacao direta significativa com massa de 100 graos, tendo-se destacado os cultivares Tertulha e CEP 53, com produtividade de graos acima de 3,7 t ha-π. Palavras-chave: agrupamento, Glycine max (L.) Merr., divergencia genetica.

Growth, phenology, and seed viability between glyphosate-resistant and glyphosate-susceptible hary fleabane

Glyphosate is the herbicide most used worldwide. In cropping systems that rely on repeated applications of glyphosate or cultivate genetically modified soyabean crop, there are numerous cases of glyphosate resistant weeds, including Conyza bonariensis. Differences among competitive ability of Conyza spp. have been found. However, little information is available on the fitness costs related to glyphosate resistance in Conyza bonariensis. We evaluated growth, phenology, and seed viability of glyphosate-resistant (GR) and glyphosate-susceptible (GS) Conyza bonariensis from Brazil, in 2012 (fall/winter) and 2013 (spring/summer). When grown alone, in pots, C. bonariensis GR biotype developed more rapidly than the GS biotype, as evidenced by their earlier bolting, flowering, and seed set. In 2012, GR biotype showed 221.9 cm of plant height compared to 181.1 cm from GS, at the flowering time. In both years, the seed production per plant was superior for GR biotype, showing germination higher than 80% against 66.5% from the GS biotype. Thus, C. bonariensis GR biotype confirmed no fitness penalty also showing characteristics that allow us to infer in superior competitive with the absence of the herbicide. It is important to point out that the biotypes evaluated here have different genetic background and the differences between them may not be fully attributed to the resistance to glyphosate. However, the GR biotype can persist in the environment and outcompete with GS biotypes regardless of further glyphosate selection of pressure.

Genetic divergence among maize hybrids by morphological descriptors

Two experiments with 25 maize commercial hybrids were carried out in a direct sowing system in Southern Brazil in the harvests of 2009/2010 and 2010/2011. Quantitative descriptors were used with the objective of determining the genetic divergence and the relative contributions of traits among hybrids for extraction of inbred lines. This study was carried out in Oxisol soil using a randomized block design with four replicates. Data were subjected to combined analysis of variance, and based on the multivariate analyses, Tocher and average linkage (UPGMA) cluster analyses, based on generalized distance of Mahalanobis, to quantify divergence in addition to Singh criterion to validate trait with the most contribution. The multivariate methods were consistent with each other, and the weight of 100 grains was the trait that contributed most to the divergence and had similar behavior in grain yield between hybrids in both years. Furthermore, this descriptor representing significant genetic variability for crossings and lines extraction to hybridization between BM 3061, ATL 200 and P 30B39 Y.