Selection and estimation of the genetic gain in segregating generations of papaya (Carica papaya L.)

F.F Silva,G.A Ferreguetti,M.G Pereira,H.C.C Ramos,A.P.C Gabriel,T.N.S Pereira,P.C Damasceno Junior,A.P Viana

doi:10.12702/1984-7033.v08n01a01

Abstract

Quite contrary to the fact that Brazil is the world’s largest papaya (Carica papaya L.) producer (Nehmi et al. 2002), the alternatives in the choice of commercial cultivars and/or hybrids for planting that would meet national as well as international market demands are very limited. Few studies of improvement have been developed aiming at new superior cultivars and, consequently, the enlargement of the genetic basis for cultivation. Besides, the costliness of hybrid papaya seeds of the Formosa group, generally imported from Taiwan at 3000 to 4000 dollars per kilogram (Pereira 2003), has caused many fruit farmers to successively plant the hybrid generations F2, F3 and F4, resulting in numerous problems, above all the loss of vigor and segregation for fruit shape. The genetic improvement of papaya in Brazil can, along with good management practices, contribute substantially to yield increase and improve fruit quality traits. This objective can be reached, partly, via basic information on inheritance of the main agronomic traits that one wishes to improve, as well as on the genetic variability available for improvement. In connection with the computation of genetic variances and means, it is of fundamental importance to establish estimates of other genetic parameters, such as the coefficient of heritability and of genetic variation, index of variation and genetic correlations to predict gains, so the viability of determined improvement ABSTRACT In Brazil, papaya is sustained by a narrow genetic basis, with few genetically distinct cultivars for planting. Therefore, this study aimed to select and estimate the direct and combined genetic gains for commercial fruit yield (Yld Plt-1) in segregating generations of papaya. Six traits were simultaneously targeted in combined selection and were attributed weights associated to agronomic values. Direct selection however was based on Yld Plt-1 only. Results indicated genetic variability in the segregating generations for the evaluated traits and although combined selection achieved a lower genetic gain in Yld Plt-1, it offers greater chances of success in the following generations since favorable and unfavorable agronomic traits of papaya are considered. These results motivated the recommendation to advance generations with 30 plants, selected from a total of 345 plants, considering all segregating treatments.

Highlights

Quite contrary to the fact that Brazil is the world’s largest papaya (Carica papaya L.) producer (Nehmi et al 2002), the alternatives in the choice of commercial cultivars and/or hybrids for planting that would meet national as well as international market demands are very limited
Few studies of improvement have been developed aiming at new superior cultivars and, the enlargement of the genetic basis for cultivation
The segregating generations were derived from the initial crossing between the dioecious genotype Cariflora and the cultivar Sunrise Solo 783 (SS 783)

Summary

Introduction

Quite contrary to the fact that Brazil is the world’s largest papaya (Carica papaya L.) producer (Nehmi et al 2002), the alternatives in the choice of commercial cultivars and/or hybrids for planting that would meet national as well as international market demands are very limited. Few studies of improvement have been developed aiming at new superior cultivars and, the enlargement of the genetic basis for cultivation. The genetic improvement of papaya in Brazil can, along with good management practices, contribute substantially to yield increase and improve fruit quality traits. This objective can be reached, partly, via basic information on inheritance of the main agronomic traits that one wishes to improve, as well as on the genetic variability available for improvement. In connection with the computation of genetic variances and means, it is of fundamental importance to establish estimates of other genetic parameters, such as the coefficient of heritability and of genetic variation, index of variation and genetic correlations to predict gains, so the viability of determined improvement program can be evaluated and the most efficient selection strategy can be adopted (Vencovsky 1969)

Objectives

Methods

Results