General and specific combining ability in the selection of polliniser cultivars of hybrid pear trees (Pyrus communis x P. pyrifolia)

Abstract

The major limiting factor in the production of pears in the tropics are the reduced number of pears cultivars adapted and the lack of knowledge of potential pollinisers among the existing cultivars. The pear tree has gametophytic incompatibility requiring a polliniser cultivar. For commercial pear tree growing, in addition to flowering synchrony and gametophytic compatibility, the metaxenia effect, which influences fruit quality, should also be considered when choosing the polliniser cultivar. This study was conducted to estimate the general combining ability (GCA) and specific combining ability (SCA) in diallel crosses to assist in the selection of pollinisers for hybrid pear tree cultivars (Pyrus communis x Pyrus pyrifolia) adapted to the low chill areas. Self-pollinations and cross-pollinations among four pear cultivars (Cascatense, Centenária, D'água, and Primorosa) were carried out in two seasons. The variables fruit set percentage, viable seed percentage, fruit mass, fruit length, fruit diameter, °Brix, and pH were evaluated. Afterward, a diallel analysis was performed, following the Griffing method 1, model 1, to estimate the GCA, SCA, and RE from the parents, F1 hybrids, and reciprocal F1 hybrids obtained in the crosses. The results revealed that Centenária showed a positive additive effect for the variables studied. The cross Primorosa x Centenária showed a high positive effect for all the evaluated traits. These results suggest the existence of a polliniser effect of the hybrid pears cultivars for the characteristics studied. This study presents information of significant value for growers interested in planting pears trees in the tropics and those involved in pears tree breeding.