Degree of apomixis in Chinese chive (Allium tuberosum) estimated by esterase isozyme analysis.

Abstract

The degree of apomixis of six cultivars of Chinese chive (Allium tuberosum ROTTL.) (2n= 32, 4x) was estimated by electrophoretic analysis of leaf esterase (EST) in progenies obtained from crosses between these cultivars. In each progeny, more than 90% of the seedlings showed the same zymogram as their pistillate parent, the remaining seedlings showing hybrid zymograms. The differences between maternal and hybrid zymograms were clear and unmistakable. The degree of apomixis was therefore calculated to be higher than 90% for each cultivar tested. For two progeny arrays the results of the electrophoretic analysis were supported by simultaneous examination of two morphological traits, namely, outer tepal length and first flowering month. Among the seedlings showing the maternal EST zymogram, two dihaploids (2n= 17, 16), one each in two progenies, were detected by cytological examination of root tips. Those dihaploids being eliminated, the degree of apomixis estimated by the isozyrne analysis was reduced by 1% resp. 2% for these progenies. This modification, however, was of little significance because of the infrequent occurrence of dihaploids. The present results indicate that a progeny test exclusively based on the EST analysis gives only a slight overestimation of the degree of recurrent apomixis in Chinese chive and that Chinese chive is a facultative apomict wlth a high degree of apomixis.