Unilateral cross-incompatibility between Camellia oleifera and C. yuhsienensis provides new insights for hybridization in Camellia spp

Camellia yuhsienensis was used to cross with oleifera improve the resistance of oil camellia anthracnose. However, unilateral cross-incompatibility (UCI) between C. and found during breeding process. Five C.oleifera cultivars four uhsienensis materials were tested confirm UCI . ‘Huashuo’ (HS) ‘Youza 2’ (YZ2) represent these two species characterize UCI, including pollen tube growth, fertilization fruit development. The results demonstrated that prevalent asynchronous flowering period a pre-pollination barrier limited mating under natural conditions. Interspecific tubes observed through styles plants, though growth rates differed considerably. At 96 hours after pollination, YZ2 barely entered ovule, but remained at base style became swollen. HS ovule 48 double observed, seeds developed commonly. Relative compatible combinations, most unfertilized ovules in incompatible combinations failed grow, turned brown 150 days fruits smaller than expected uneven enlargement. Investigations on both semi- vivo vitro gave us new idea for thought: has stronger inhibitory effect interspecific tubes, while calcium alleviates prevent appearance abnormal morphology. This study provides useful information hybridization understanding reproductive isolation mechanisms programs genus