Study on phenological growth stages of kiwifruit (Actinidia deliciosa) Hayward in the west of Guilan

Kiwifruit as a new commercial crop in comparison with other crops that are grown in the similar climatic conditions has a high economic return. On the other hand, this fruit has better quality in Iran than that in other kiwifruit production countries. Management practices such as pruning, application of growth regulators, fertilizers, pesticides, mechanical natural and hand pollination, flower and fruit thinning, harvest time, etc. rely on the recognition of certain phenological stages. Therefore, the objective of this study was to describe the phonological growth stages of a Hayward kiwifruit cultivar growing under the west of Guilan using the BBCH code and to calculate the heat requirements that help predict the time to reach each phenological stage.
This experiment was conducted in a randomized complete block design with 3 replications of 4 trees. Fruiting branches on each 4 tree (2 on each side) were marked for assessed. Principal and secondary phenological growth stages of development using the BBCH scale for 2 years in the west of Guilan (Astara) on mature vines were determined. Fruit growth curve, with measuring dimensions and equivalent water, TSS changes with hand refrectometer and the effect of temperature changes on TSS and flowering and fruit development were studied. Heat requirements were calculated as GDD.
Eight Principal phenological growth stages on kiwifruit include: stage 0 (bud development), stage 1 (leaf development), stage 3 (shoot development), stage5 (inflorescence emergence), stage 6 (flowering), stage 7 (fruit development), stage 8 (maturity of the fruit) and stage 9 (Senescence, beginning of dormancy) that began with the beginning of bud swelling in the 17th of March and terminated on the 25Th of December. The time of secondary phenological growth stages and some management practices related to each of these stages of BBCH scale also mentioned. Broken of branch buds increased from the base to the top of the shoots, so that all dormant buds were in the base. The percentage of bud break, and the number of fruitful shoots were affected by the year. The curve of fruit growth was double sigmoid and increased fruit soluble solids of fruit was about 3 months later. After dormancy breaking and from beginning of bud swelling, Hayward kiwifruit cultivar required 429.275±10.67 GDD to reach full bloom, 1187.5±65.8 GDD to reach 50% of final fruit size and 2763.58±19.92 GDD before the fruit could be harvested.
Determine of heat requirements is important for predict of the management time, so that the temperature difference between days in different years affected the development stages. The index can be used to predict developmental stages and thus to apply administrative tasks such as flowers thinning, fruit thinning, green pruning, winter pruning, fertigation, pest and disease control and also be used to expecting of physiological fruit maturity.