Combined Selection in Backcross Population of Papaya(Carica papaya L.)by the Mixed Model Methodology

The selection of superior genotypes based on the simultaneous response to several characteristics of agronomic importance is a key strategy to overcome the scarcity of available varieties of papaya. This study aimed to apply the combined selection by using distinct selection indexes based on both the genetic values obtained by the REML/BLUP methodology and the real measured values to select agronomically superior genotypes of papaya within backcross progenies. The combined selection was carried out based on genetic and phenotypic values, original and standardized, multiplied by the agronomic weights. The results of the analysis of genetic parameters indicate that the evaluated progenies have expressive genetic variability for the considered traits, and that there are real possibilities of genetic progress with the selection. Among the analyzed indexes, the one based on standardized genetic value presented greater consistency in the ranking of genetic material, demonstrating the advantage of data standardization. Five progenies belonging to the BC1 generation, and five to the BC3 generation were selected using this index. A total of 27 plants ag-ronomically superior were selected within the top five progenies and recommended for generation advance, 23 being selected by combined selection and 4 using the direct selection for the four mainly characters in papaya breeding program: production, pulp and fruit firmness and soluble solids. Beyond the selection of superior genotypes for the development of future inbred lines, this study also allowed defining the best strategy to apply the combined selection in papaya using pre-dicted breeding values obtained by BLUP. This strategy may allow higher accuracy in the selection process, thus increasing the chances of success of the breeding programs.

Emergence of Conilon Coffee Seedlings Originating from Seeds Treated with a Sodium Hypochlorite Solution

The coffee seeds are problematic for the physiologycal quality, featuring low speed of seedling emergence. In this sense, this work was developed with the objective of evaluating the effect of sodium hypochlorite in the removal of the parchment and in the emergence and seedlings development of conilon coffee in nursery conditions. Coffee seeds of the variety Victoria were used, which were harvested in the cherry stage and pulped by hand. Seeds were dried in an oven with forced ventilation until reaching moisture contents of 35%, 30% and 25% wet basis. Then, the seeds with parchment were soaked in a sodium hypochlorite solution with concentrations of 4%, 5%, 6% and 7% active chlorine for 3 and 6 hours. For each moisture content, two additional treatments were added consisting of seeds with parchment and seeds in which the structure was removed manually. The characteristics evaluated were: emergence speed index, total emergence, dry mass of the shoots and root system. Utilization of sodium hypochlorite promoted an acceleration in seedling emergence speed similar to the method for manual removal of the parchment when using concentrations of 4%, 5%, 6% and 7% for 3 hours, at all moisture contents.