ISHS Acta Horticulturae 444: III International Symposium on Kiwifruit
PROGRESS IN BREEDING HERMAPHRODITE KIWIFRUIT CULTIVARS AND UNDERSTANDING THE GENETICS OF SEX DETERMINATION |
| Author: | M.A. McNeilage |
| Abstract:
2723 seedlings in 19 families were produced from crosses using sex variants of kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang and A.R. Ferguson). There were 6 types of cross: female x hermaphrodite, female x inconstant male, hermaphrodite x inconstant male, hermaphrodite selfed, inconstant male x inconstant male, and inconstant male selfed. The aims of the study are to (i) describe variation in sex expression, (ii) compare sex ratios between and within the 6 cross-types, (iii) construct a model for the genetics of sex determination, (iv) measure variation in fruit size, (v) select hermaphrodite seedlings with commercial potential, and (vi) select hermaphrodite seedlings for use in ongoing breeding. Although 87% of seedlings assessed to date have been males or females, 4 sex variants have been identified: hermaphrodites, neuters, inconstant males and inconstant females. Sex ratios and frequencies of sex variants associated with the 6 cross-types suggest a simple genetic system determines basic sex phenotype (male-female dimorphism), while additional genes may be responsible for sex variants. 55 hermaphrodites have been identified and more are expected, as some families still contain immature vines and 34 % of mature vines have not yet been pollen-tested. Several hermaphrodites produce fruit of comparable size to ‘Hayward’, the female cultivar on which most kiwifruit production worldwide is currently based. Further crosses have been made. | |
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