Abstract
The objective of this paper was to estimate the genetic parameters and additive genetic values in segregating populations of papaya using the mixed model methodology. Two F2 populations from Tainung and Calimosa hybrids were evaluated. The experimental design was an augmented block with four replicates, and Golden and Calimosa cultivars were the common treatment. Estimates of individual heritability were high for fruit length (FL) and weight (FW), moderate for fruit diameter (FD), and low for total soluble solids (TSS) and fruit firmness (FF). Considering FF and TSS as main traits for selection, genotypes of Calimosa-F2 population showed better performance to FF, but worse concerning TSS. It was selected 18.3% and 24.6% of plants from Tainung-F2 and Calimosa-F2 populations, respectively. Negative correlation between TSS and FF was not able to reduce the genetic gains. The segregating populations from Calimosa hybrid are more promising for the selection of papaya lines.
Highlights
The most commercially grown papaya varieties (Carica papaya L.) belong to Solo and Formosa groups, which are basically represented by varieties and hybrids, respectively
Estimates of individual heritability were high for fruit length (FL) and weight (FW), moderate for fruit diameter (FD), and low for total soluble solids (TSS) and fruit firmness (FF)
The genetic coefficients of variation at individual level (CVgi%), which express the amount of existing genetic variation in percentage of average, indicated values with small magnitude for FD, TSS and FF, whereas FL and fruit weight (FW) values were significant, indicating greater variation in populations segregating for these traits (Table 1)
Summary
The most commercially grown papaya varieties (Carica papaya L.) belong to Solo and Formosa groups, which are basically represented by varieties and hybrids, respectively. From the genetic improvement point of view, the genetic variability available in the segregating populations can be exploited to produce new hybrid combinations through the selection of new papaya lines. Early selection of plants in the breeding program presents low efficiency when compared with the following stages of selection, given the low values of heritability for important agronomic traits in accordance with some species (Skinner et al 1987, Backes et al 2002). According to Matsuoka et al (2005), an interesting strategy at this stage is the selection of the best plants carried out with higher selection intensity for traits with high heritability, without forgetting the secondary characteristics to prevent the disposal of valuable genotypes
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