The study on the compatibility of interspecific hybridization between Castanea henryi and Castanea mollissima was carried out to overcome the obstacles of flowering period between C. henryi and C. mollissima, and to provide a theoretical basis for the creation of specific germplasm of Castanea.

Four varieties of C. henryi ‘Huali 1’ ‘Huali 2’ ‘Huali 4’ and ‘Dili 1’ are used as female parents and C. mollissima ‘Tanqiao’ as male parent to carry out interspecific cross pollination, and natural pollination of four C. henryi varieties as control to compare and analyze their compatibility and fruit quality.

The compatibility between four varieties of C. henryi and C. mollissima ‘Tanqiao’ was in the following order: ‘Deli 1’ > ‘Huali 4’ > ‘Huali 1’ > ‘Huali 2’, the highest seed setting rate was 42.41%, and the lowest seed setting rate was 28.93%. The growth trend of hybrid fruit and natural pollinated fruit was slow-fast-slow, and the growth trend of fruit was not affected by interspecific hybridization. The fruit ripening period of four interspecific hybrid combinations was affected by the male parent C. mollissima ‘Tanqiao’. The use of C. mollissima ‘Tanqiao’ pollination significantly increased the single grain quality, while also markedly raising their starch content, vitamin C content, and total flavonoid content, in which the single grain quality increased by 4.07%-27.92%, and the starch content increased by 5.21%-21.21%. The content of vitamin C increased by 6.37%-116.49%, and the content of total flavonoids increased by 9.80%-95.50%. The comprehensive evaluation of fruit quality by comprehensive direct evaluation method and average membership degree method showed that C. mollissima ‘Tanqiao’ improved the nut quality of ‘Huali 1’ most significantly.

The interspecific hybridization between C. henryi and C. mollissima has a certain compatibility, and different female parent varieties have different compatibility. The maturation period, nut size, nut quality and the number of nuts in a single bulb were greatly affected by the male parent. The interspecific hybridization between C. henryi and C. mollissima is a potential way to improve the quantity and fruit quality of individual spiny nuts.