DESEMPENHO E DIVERSIDADE GENÉTICA DE HÍBRIDOS PRÉ-COMERCIAIS DE SORGO SACARINO NO CENTRO-OESTE E SUL BRASILEIRO

Abstract

Sorghum (Sorghum bicolor (L) Moench) is a Poacea family species, from African origin and arrived in Brazil in the twentieth century. According to the Ministério da Agricultura, Pecuária e Abastecimento in 2018 there are 583 cultivars of sorghum in Brazil and over the past 30 years has shown a considerable increase in production. Sorghum is commonly grown in arid and warm climate regions, as has drought and heat resistance due to its C4 type photosynthetic metabolism. From a cytogenetic point of view, all sorghum types have the same chromosome complement of 2n = 20, and are now recognized as variants of the same plant. In conducting a breeding program, success is related to the existence of variability in the evaluated population. Research that prioritizes diversity and variability, taking into account both dissimilarity or genetic similarity in crops of great agronomic importance, is becoming increasingly relevant for plant breeding. Procedures for estimating dissimilarity measures based on quantitative (Euclidean or Mahalanobis distances), binary and multi-categorical, between pairs of genotypic materials, for cluster analysis to evaluate genetic diversity, are of considerable importance. After the dissimilarity matrix is generated using the Mahalanobis distance, the optimization clustering methods are used to establish groups where there is homogeneity within the groups, and heterogeneity between them. In optimization methods, such as Tocher's, the group of individuals (genotypes) are divided into nonempty and mutually exclusive subgroups by maximizing or minimizing some reestablished measure. It establishes the criterion that the average dissimilarity measures within each group should be less than the average distances between any group.