Seed Paternity Analysis Using SSR Markers to Assess Successful Pollen Donors in Mixed Olive Orchards.

Gabriela Vuletin Selak,Slavko Perica,Dunja Bandelj,Julián Cuevas,Marina Raboteg Božiković,Petar Pujic,Alenka Baruca Arbeiter

doi:10.3390/plants10112356

Abstract

The olive tree (Olea europaea L.) is a wind-pollinated crop that exhibits an extreme alternate bearing habit. To improve fruit set, several methods have been used to determine the most successful compatible combinations of cultivars. In this study, priority is given to seed paternity analysis based on simple sequence repeats (SSRs), microsatellite markers used for the identification of potential pollen donors of cultivar ‘Oblica’ in a mixed olive orchard during two consecutive years. Seven microsatellite primers were successfully used to examine the paternity of olive embryos from ‘Oblica’ mother trees. Embryos were considered as a product of self-fertilization if only maternal alleles were present, but not a single case of self-fertilization was found among all the embryos analyzed. Two dominant pollen donors were not the closest nor the cultivars with the highest number of trees in the orchard, suggesting that cross-compatibility may have a key role in determining pollen donor success. In our earlier studies, pollen tube growth and fertilization success correlated with fruit set when controlled crosses between cultivars were performed; however, some discrepancy might appear compared to paternity analyses when mother trees have a free choice among different pollen sources from cultivars growing in their surroundings.

Highlights

The olive, Olea europaea L., is a wind-pollinated, hermaphrodite, preferentially allogamous crop extraordinarily important in the Mediterranean area
We considered the distance in meters as the distance of the mother trees to the closest tree of each potential pollen donor
Seven microsatellite loci were used for the identification of the pollen donor and offspring genotypes

Summary

Introduction

The olive, Olea europaea L., is a wind-pollinated, hermaphrodite, preferentially allogamous crop extraordinarily important in the Mediterranean area. Olive presents abundant biennial flowering, a relative poor fruit set, even in its ‘off’ season [1]. The constraints leading to low fruit set include alternate bearing [2], male-sterility [3], pistil abortion [4,5], and self- (SI) and cross-incompatibility [6,7]. SI is certainly the most important reproductive barrier in olive. SI prevents self-fertilization based on mechanisms involving the recognition and rejection of self-pollen [8,9]. A higher success of cross-pollination over self-pollination has been generally reported for olive and the self-incompatible condition of olive is no longer disputed [10,11,12,13]

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Conclusion