Bruno Portela Brasileiro

Selection strategy in families of energy cane based on biomass production and quality traits

Abstract The aim of this study was to identify the traits that most affect production of sugarcane, fiber and lignin content (LIG) with a view toward optimizing the process of assessment and selection of families of energy cane. Fifty full-sibs families were assessed using an incomplete-block design, with five replications. The traits assessed were mean stalk height (SH), mean stalk diameter (SD), mean number of stalks per plant (NS), mean stalk weight (SW), fiber content (FIB), LIG, tons of cane per hectare (TCH), tons of fiber per hectare (TFH) and tons of lignin per hectare (TLH). Based on path analysis, it was possible to observe that the traits SW and NS, in that order, exhibited the greatest direct effects on TCH, TFH, and TLH. These traits they were indirectly affected to a greater degree by NS. The direct effects of FIB, LIG, SH, and SD on TCH, TFH, and TLH were smaller than the residual effects on the analyses carried out, showing their little importance in the selection process. The increase of TFH and TLH mainly occur due to greater biomass production, which is associated with greater tillering capacity and with the SW of the families. Thus, selection of families with greater FIB might not show genetic gains if the mean values for TCH of their offsprings are low. Therefore, selection of the best families for energy cane should be carried out based on TCH, which may be estimated by way of NS and SW.

Consistency of the results of path analysis among sugarcane experiments

The aim of this research was to evaluate the consistency of path analyses in sugarcane experiments based on genetic, phenotypic and genotypic correlations. Forty-four analyses were made with a view toward quantifying the direct and indirect effects of stalk height (SH), stalk diameter (SD) and number of stalks (NS) on sugarcane weight (SW). NS had the greatest direct effect on SW in all the analyses with the use of genetic and phenotypic correlations and in 12 analyses with use of the genotypic correlations. SD had a high direct effect on SW, going beyond NS in only one experiment, while SH had the lowest direct effect on SW in most of the experiments. The results showed greater consistency with the use of genetic and phenotypic correlations. In the balanced experiments, the phenotypic and genetic correlations showed equivalent results. NS is the main determinant of changes in sugarcane production.

Genetic diversity and coefficient of kinship among potential genitors for obtaining cultivars of energy cane

The aim of this study was to evaluate the genetic diversity and coefficient of kinship in 50 sugarcane genotypes, in addition to identifying potential parents for obtaining cultivars of energy cane. Diversity analysis was carried out based on the evaluation of morphological and agronomical characteristics. The coefficient of kinship was obtained from information on pedigree. According to analyses carried out, genotypes were separated into two groups. Group G1 consisted of 13 genotypes from the species Saccharum spontaneum and Saccharum robustum. The other 37 genotypes were from back-crosses with Saccharum officinarum, and were allocated to group G2. The genotypes displayed low values for genetic similarity and coefficient of kinship, indicating broad genetic variability in the population. Carrying out crosses involving genotypes from group G1, especially those with a fibre content of over 17% (IJ76-293, 57NG12, IN84-82, IN84-88, IM76-228 and UM69/001), with genotypes from group G2 which have high stalk yield (RB92579, RB83102, RB047232, RB867515, RB971723, RB937570, RB011941, RB75126, MEX68-200, Co62175 and CP691052), should be explored, with the aim of developing energy cane cultivars. Analyses of diversity and of the coefficient of kinship made it possible to identify two heterotic groups. Moreover, it was possible to identify two potential parent groups for obtaining energy cane cultivars. Genetic distances which are based on both morpho-agronomical data and on pedigree, should be used in a complementary way, with a view to having more information when choosing the best parents.