Juarez Campolina Machado

Comparação de métodos de seleção de genitores e populações segregantes aplicados ao melhoramento de trigo

The methods used for selecting crosses in one crop species are not necessarily appropriate for others. The present study aimed to evaluate the application of diallel analysis, genetic diversity, parental average, and the Jinks and Pooni method for the selection of parents and superior segregating populations for the grain yield character in wheat. Thus, two experiments were conducted and the treatments were arranged in lattice (experiment I) and randomized blocks with individual information within the plot (experiment II). Twelve parental individuals and 36 segregating populations in the F 3 generation resulting from the crossing of these parents in a partial diallel arrangement were evaluated. The application of the evaluated methodologies led to distinct results. The parental average and genetic diversity alone are not efficient prediction methods. The methodology of Jinks and Pooni presents practical limitation because it is not adequate for wheat crop system. Among the evaluated methodologies, diallel analysis is the most promising method for the identification of parents and superior segregating populations.

Genetic parameters of wheat populations in environments with contrasting temperatures

The objective of this study was to estimate genetic parameters of wheat segregating populations grown in environments with different thermal conditions. Thus, two experiments were carried out at Universidade Federal de Vicosa, Brazil. A 16 by16 square lattice design was used with two replications, where 240 families from eight segregating populations, 30 families from each population, plus 16 parents were evaluated. In the first experiment, sown in February 2007 (summer), S0:2 families were evaluated. In the second one, in June 2007 (winter), S0:3 families were evaluated. Grain yield and thousand grains weight were recorded. So, the most promising population to be grown under different levels of temperature is the Population II originated from BR24/Alianca//EP93541/CPAC9662. It was verified that the thermal conditions might interfere in the wheat genotypes performance and also in the genetic parameters estimates.

Pyricularia grisea causando manchas foliares na cultivar BRS capileto de capim-elefante (Pennisetum purpureum Schumach.) X milheto (Pennisetum glaucum (L.) R. Br.)

Schumach.) e,reconhecidamente, uma das gramineas forrageiras de mais altopotencial produtivo, adaptando-se muito bem as condicoes de climae solo de praticamente todo o Brasil. Contudo, uma das principaisdificuldades existentes para a expansao do cultivo do capim-elefanteesta relacionada a sua forma de propagacao, realizada por meio deestacas, o que aumenta o custo de transporte e plantio da forrageira,impossibilita o armazenamento do material propagativo por longoperiodo, alem de dificultar a distribuicao das cultivares melhoradas.Os hibridos interespecificos hexaploides, obtidos pela combinacaogenetica entre o milheto (