Objective This paper aims to screen the key climate factors affecting the quality of chestnut, to evaluate the climate adaptability of chestnut in different ecological regions and its suitable planting regionalization, and also to provide theoretical basis for the introduction and scientific planting of chestnut.
Method 105 Chinese chestnut varieties (including superior lines) from 4 ecological regions in China (the Huanghuaihai, the Northwest, the middle and lower reaches of the Yangtze River, and the Southwest) were taken as the research objects. The differences of phenotypic traits such as single nut mass, fruit shape index, and the internal qualities such as soluble sugar, starch, and protein were analyzed. 12 climate factors from 24 main Chinese chestnut planting areas in the 4 regions were selected for principal component analysis to screen the climate factors that are most closely related to the formation of Chinese chestnut quality. The climate quality evaluation model of Chinese chestnut was constructed by stepwise regression. Climate adaptability index (CAI) was used to evaluate the climate adaptability of Chinese chestnut.
Result (1) There were significant differences in phenotypic traits and intrinsic qualities of chestnut in different ecological regions. The single grain mass and fruit shape index in the middle and lower reaches of the Yangtze River were significantly higher than those in other regions. The soluble sugar and amylopectin/amylose ratio were the highest in the Huanghuaihai region. (2) The main climate factors affecting the quality of chestnut nuts were heat factor, followed by light factor and water factor. There was a significantly positive correlation between single grain mass and annual mean temperature and growing season precipitation, a significantly negative correlation between single grain mass and temperature difference, and a significantly negative correlation between fruit shape index and temperature. There were significant positive correlations between water content and annual precipitation, average temperature in growing season and precipitation in growing season. Soluble sugar had significantly positive correlation with annual sunshine duration, temperature difference in growing season and sunshine duration in growing season. Amylopectin/amylose ratio was significantly positively correlated with sunshine duration, average temperature, temperature difference and sunshine duration in growing season. Protein was positively correlated with annual mean temperature, and negatively correlated with annual sunshine hours and growing season sunshine hours. (3) According to CAI, 24 main planting areas of Chinese chestnut in the four regions can be divided into the most suitable area, the more suitable area and the suitable area. The CAI value of the northern Huanghuaihai area reached 0.90−0.96, which was the most suitable area; the CAI value of the east, northwest and southwest of the Huanghuaihai area was 0.81−0.89, which was a suitable area; the middle and lower reaches of the Yangtze River had the lowest CAI value, 0.71−0.77, which was suitable for the region.
Conclusion The climatic conditions of large temperature difference, high average temperature, long sunshine hours in the growing season are favorable for the formation of sweet and waxy quality of chestnut nuts.