Inter-specific and Inter-generic Hybridization Compatibility of Eriobotrya Species (Loquat) and Related Genera

We studied the cross-compatibility among 91 inter-specific combinations and 21 inter-generic combinations in 7 Eriobotrya plants and 2 related genera (Raphiolepis indica Lindl. and Photinia serrulata Lindl.) using emasculation, bagging, and artificial pollination. Our results showed that 28 of the 91 inter-specific combinations set no fruit, which means nearly 30% of the combinations were incompatible. In the remaining 63 combinations, most showed partial cross-compatibility, and a few showed complete cross compatibility. Eriobotrya plants were incompatible with plants from their related genera (R. indica Lindl. and P. serrulata Lindl.). Backcrossing produced 5 compatible combinations, which could set fruits and produce F1 progeny but only after embryo rescue. Fruit setting ratios varied among various species used as male or female parents. E. prinoides Rehd. & Wils., common loquat (E. japonica) and Eriobotrya × daduheensis, used as female parents resulted in an average fruit-setting ratio of 36.2%-58.2%. E. deflexa Nakai and its two forms, and E. elliptica Lindl. as female parents resulted in 2.9%-16.3% average fruit-setting ratio; however, the fruit set ratio was higher (22.4%-43.1%) if they were used as male parents. Failure of E. deflexa f. koshunensis Nakai × E. prinoides Rehd. & Wils. hybrids to set fruit could be attributed to sporophytic incompatibility.