Preliminary results of self- and cross-incompatibility and parthenocarpy in lemon

Self-incompatibility and parthenocarpy in Citrus are very important traits for fruit production because they result in seedless fruit. Nevertheless, without parthenocarpy, cross-pollination is required to achieve stable fruit production. In lemon, little is known about floral biology, which is a very important trait to be considered in the breeding of this Citrus species. In the present study, we examined the self- and cross-compatibility, as well as parthenocarpic performance of six lemon cultivars (‘Fino 49’, ‘Verna 51, ‘Fino 95’, ‘Eureka’, ‘Messina’ and ‘Lisbon’) and their effect on fruit set, seed number and kind, and fruit size. The fruit set percentage in parthenocarpy was very low for all lemon cultivars. ‘Lisbon’ was the cultivar with the greatest parthenocarpy capacity (fruit set: 20%). Most cultivars were moderately self-compatible, with a fruit set between 20 and 40%, except for ‘Verna 51’, for which less than 10% was achieved. A high number of aborted seeds was observed in self-pollinated fruits. In a cross-pollination experiment, ‘Fino 49’ was largely compatible with most of the other five lemon cultivars (fruit set: 20-35%); however, these results were similar to those obtained with the self-pollination experiment. ‘Verna 51’ and ‘Fino 95’ were the least cross-compatible cultivars (fruit set: 10%). No differences on fruit size were observed between crossings, except for ‘Verna 51’. When this cultivar was the female parent in the cross-pollination experiment, fruit size was larger than for this cultivar in self-pollination or parthenocarpy experiments. The number of seeds and aborted seeds in cross-pollination was similar to that of self-pollination, except for ‘Verna 51’ fruits, which had fewer seeds in self-pollination than in cross-pollination experiments.