Frequency of citrus hybrids from controlled crossings: seed germination in seedbeds versus in vitro embryo cultivation

Abstract

The frequency of citrus hybrids obtained from controlled crossings was studied, comparing seed germination in seedbeds with embryos cultivated in vitro. The effect of peeling off the seed teguments on the germination was also studied. The 'Clementina Palazelli' and 'Sunki' mandarins, 'Rangpur Santa Bárbara' lime, 'Volkamer Catania 2' lemon and sour oranges 'Common' and 'Double Calice' were used as female parents. The male parents were Poncirus trifoliata and hybrids of this species. A completely randomized design was used, with three seed treatments: intact; without the outer tegument (testa); and, without both the outer and inner (tegmen) teguments. The in vitro embryo culture was used as control. Evaluations included the speed of seed germination, percentage of germination and polyembryony, size and number of embryos per seed and percentage of hybrid seedlings. The removal of seed teguments accelerated the germination in all varieties; improved the percentage of germination only in 'Sunki' mandarin and 'Volkamer' lemon. The percentage of zygotic seedlings that were rescued was higher in the in vitro embryo culture, in such a way that the advantage in using this technique was directly proportional to the degree of polyembryony of the female parents used in the crosses.