A study on the relationship between dwarfing cultivation and load of Yueyanghong apple

Abstract:【Objective】The study investigated the relationship between tree structure, leaf chlorophyll content, photosynthetic indexes and fruit yield and quality and fruit load【. methods】Ten-year old trees of Yueyanghong /77-34/ Malus baccata Borkh. were used as the experimental material to study the ef- fects of fruit load on tree structure, leaf chlorophyll content, photosynthetic indexes and fruit quality. testdesignforthreetreatments,treatmentIcontained30000kg·hm-2 load,treatmentIIcontained37 500kg·hm-2 load,treatmentIIIcontained45000kg·hm-2 load.【Results】Thetotalnumberofshootsin treatment II was1046×103 per hm2, which was higher than that in treatment I and treatment II, which was 138×103 per hm2 and 37×103 per hm2, respectively. The number of medium and short branches were largestintreatmentIII(1009×103 perhm2),followedbytreatmentII(1046×103 perhm2),andsmallest in treatment I (908×103 per hm2). As for long branches, the treatment I had the largest number. There were significant differences among different treatments. At the stage of fruit full maturity, higher shoot number and the higher proportion of medium and short shoots contributed to higher and stable yield of the tree in next season. Trees in treatment II had a better tree structure with a larger proportion of medi- um and short shoots and a larger total number of shoots, while the proportion of long shoots was lower. The ratio of long, medium and short shoots was 1∶2.7∶8.4. The total chlorophyll content in treatment IIwas significantly higher than that in treatment I and treatment III. There was no significant difference between the treatment I and treatment III. Leaf chlorophyll content in treatment II was positively cor- related with specific leaf weight. Net photosynthetic rate in treatment II was the highest, which was 17.11 μmol·m-2·s-1, followed by treatment III, 16.08 μmol·m-2·s-1, and there were great differences between treat- ment I and treatment II. The lowest stomatal conductance in treatment II was 0. 038 3 mmol · m- 2 · s- 1, which was significantly higher than that in treatment 1, but not significantly different from that in treat- ment III. The transpiration rate in treatment I and III was significantly higher than that in treatment II. Intercellular CO2 concentration decreased with the increase in net photosynthetic rate, and was the high- est in treatment I, which was significantly higher than the other two treatments. Net photosynthetic rate was inversely proportional to stomatal conductance, intercellular CO2 and transpiration rate. The photosynthetic performance and photosynthetic rate of Yueyanghong were significantly improved by treatment II. Fruit quality was affected by fruit load. Fruit load was relative lower and the single fruit weight was the largest in treatment I. Fruit shape index was significantly changed by the treatments. In terms of fruit hardness, treatment I was significantly higher than the other two treatments, while treatment II had no significant effect. Soluble solids in treatment II was the highest (13.64%), while in treatment I it was only 11.64%. The content of titratable acid in treatment I was significantly higher than that in treatment II and III, and the content of Vc in treatment II was also higher than that in treat- ment I and III. Fruit color reflected by L, a and b values in treatment II and IIIwas obviously better than in treatment I, but there was no significant different between treatment II and treatment III. In summary, fruit quality treatment II was the best.【Conclusion】Treatment II with medium load (193 per plant) had good internal and external fruit quality, which contributed to the nutrient accumulation, high yield and stable yield of the tree. The number of shoots was 1046×103 per hm2, and the ratio of long, medium and short branches was 1∶2.7∶8.4, which could overcome the problem of alternative bear- ing.