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

Han Gong; Yihong Chang; Jinming Xu; Xinran Yu; Wenfang Gong

doi:10.3389/fpls.2023.1182745

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

Front Plant Sci. 2023 Jul 3:14:1182745. doi: 10.3389/fpls.2023.1182745. eCollection 2023.

Authors

Han Gong¹, Yihong Chang¹, Jinming Xu¹, Xinran Yu¹, Wenfang Gong¹

Affiliation

¹ Key Laboratory of Cultivation and Protection for Non-Wood Forest Trees of Ministry of Education, Central South University of Forestry and Technology, Changsha, China.

Abstract

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

Keywords: calcium; interspecific hybridization; pistil-pollen interaction; pre-zygotic barrier; semi in-vivo test.

Grants and funding

This work was supported by the Natural Science Foundation of Hunan Province [grant number 2020JJ5968], Guangxi Key Laboratory of Special Non-wood Forests Cultivation and Utilization [grant number JB-20-03-02], Scientific Research Foundation for Advanced Talents of Central South University of Forestry and Technology [grant number 2018YJ002], Special Funds for the Construction of Innovative Provinces in Hunan [grant number 2021NK1007] and the Key Program of Education Department of Hunan Province [grant number 20A524].