POLYEMBRYONY AND RAPD MARKERS FOR IDENTIFICATION OF ZYGOTIC AND NUCELLAR SEEDLINGS IN Citrus

摘要

Polyembryony is one of the main obstacles in citrus breeding because identification of zygotic and nucellar seedlings is difficult by traditional means. However, polyembryony can be useful for clonal propagation of citrus rootstocks. In both cases, itis necessary to identify seedling origin in the early stages. Techniques based on DNA analyses have been a useful tool for hybrid identification. In this study, polyembryony of Citrus reshni was evaluated for three harvest years. Embryos from 25 polyembryonic seeds of C. reshni were cultivated in vitro; eleven and six embryos of monoembryonic seeds of Robinson (C. ciemenftina x Tangelo Orlando) and C. reshni were also included. Seedling DNA was extracted and used with five RAPD primers to identify seedling origin, zygotic or nucellar. Environmental conditions affected the number of embryos per seed; the percentage of polyembryonic seeds varied from 79.4 to 90.1. RAPD markers permitted the efficient identification of zygotic and nucellar seedlings of C. reshni and Robinson. Sexual origin was determined in polyembryonic and monoembryonic seeds of C. reshni; 16.6 and 83.3% of the seedlings have this origin. All seedlings of Robinson were zygotic.