Discrimination of zygotic and nucellar seedlings of five polyembryonic citrus rootstocks by isozyme analysis and seedling morphology

Abstract

SummaryIsozyme analysis using eight loci of six enzyme systems was used to distinguish zygotic from nucellar seedlings resulting from open pollination of five polyembryonic citrus rootstocks. Zygotic seedlings were detected by isozyme analysis in the rootstocks rough lemon (2.1%), trifoliata orange (2.6%), sweet orange (0.8%) and ‘Troyer’ citrange (0.8%). No zygotic seedlings of ‘Cleopatra’ mandarin were detected, but this may be due to the high proportion of homozygous loci. The zygotic seedlings had arisen by both self pollination and cross pollination of the maternal parent. There was some morphological variability amongst the zygotic seedlings but these characters could not be used to identify all of the zygotic seedlings detected by isozyme analysis.