Chilling and Heat Requirement of ‘Fengtang’ Plum

Purpose To clarify the chilling and heat requirements, and the relationship between them for flowering of ‘Fengtang’ plum, providing a basis for flowering and maturity prediction.

Methods The chilling requirement of ‘Fengtang’ plum was estimated by using 0-7.2 ℃ model, Utah model and dynamic model on the detached branches under artificial temperature control, and the effects of chilling and heat accumulation on the germination were also studied. Under field conditions, the relative phenological periods of ‘Fengtang’ plum were recorded, and the chilling and heat requirements for flowering and fruit maturing were estimated, and the optimal estimation model was defined. The relationship between chilling requirement and heat requirement was further studied by controlling chilling accumulation and increasing heat accumulation, and the correlation between chilling requirement and heat requirement in flowering of ‘Fengtang’ plum were established.

Results The dormant period of ‘Fengtang’ plum was from 42 to 54 days, and it took 51-69 days to break dormancy and 109-117 days to develop fruit. The estimated value of chilling requirement of ‘Fengtang’ plum was 142.0-385.0 chill hours (0-7.2 ℃ model, CH), 449.5-606.6 chill units (Utah model, CU), and 25.8-28.9 chill portions (dynamic model, CP). Dynamic model showed the lowest coefficient of variation, and the results of field condition estimations were consistant with that under temperature control conditions, indicating dynamic model was most suitable model for estimating chilling requirement. In heat requirement evaluation for flowering of ‘Fengtang’ plum, Richardson model showed the lowest coefficient of variation, the estimated value ranged from 5474.5 to 6609.2 GDH·℃; in heat requirement evaluation for fruit maturing of ‘Fengtang’ plum, Anderson model was more stable, showing estimated value from 40417.1 to 41892.8 GDH. The results of indoor chilling and heat compensation experiments showed that the dormancy could be broken by adding heat to make up for the lack of chilling in a certain range, and the germination of ‘Fengtang’ plum needed less heat when the chilling accumulation was increased, the flowering process accelerated. There was a negative correlation between chilling requirement and heat requirement in flowering of field ‘Fengtang’ plum.

Conclusion Among the three models, the dynamic model is the best one for the chilling requirement of ‘Fengtang’ plum, and for flowering, ‘Fengtang’ plum is a low chilling requirement and low heat requirement variety, and there is a negative correlation between the chilling requirement and heat requirement. The results of this study can provide a reference for the production, introduction, cultivation control, florescence prediction and variety breeding of ‘Fengtang’ plum.