مهسا عاشوری واجاری

Mutation by gamma radiation is used as a new technology to improve some quality traits in fruits. In this research, the effect of gamma radiation in scions of kiwifruit with different doses (0, 30, 40, 50, 60, 70 and 80 Gray) on the physicochemical properties of kiwifruit was studied. For this purpose, chisel grafting of gamma treated scions were done on kiwifruit vines in winter 1391 and after a year of no fruiting (1392), in 1393, the fruits were evaluated at harvest time and intervals of one month in the cold storage for 3 months. The results showed that fruits obtained from treated scions with dose of 40 gray of gamma radiation had the highest firmness, highest weight and lowest weight loss at harvest and during storage. Vines with treated scions by doses of 70 and 80 gray of gamma radiation did not have any fruits and remained in vegetative stage. The treatments of 50 and 60 gray of gamma radiation caused severe deformation and deep split in kiwifruits and these lost their marketability. Therefore, the firmness of kiwifruit during storage is the most important factor in the potential storage and exports, due to the positive effect of radiation of 40 gray on this factor at harvest time and during storage, as well as an increase in fruit weight, fruit yield and reduce water loss, it seems to be effective in positive changes of quality of the fruit.

The main factor affecting fruit quality and post-harvest loss in kiwifruits is improper tree nutrition. In this study, fruits were harvested from 24 different orchards in the east of Guilan province when the total soluble solid content of the fruit was 6.2°. percent the fruts was. Fruits’ mineral content such as nitrogen, phosphorus, potassium, calcium and magnesium, the mineral elements ratios and also fruits firmness were measured after harvest. Thereafter, fruits were transferred to cold storage at 0 ºC temperature and 90% relative humidity and after 15 weeks, fruit tissue firmness, water loss, ethylene content and respiration severity were measured. There was a significant positive correlation between fruits tissue firmness with fruit calcium content, but a significant negative correlation with potassium and nitrogen content, N:Ca, N+K:Ca. K:Ca and K+Mg:Ca ratios. At the end of storage, there was a significant positive correlation between fruit tissue firmness with calcium content at harvest time and a significant negative correlation with nitrogen, phosphor us and potassium content and N:Ca, N+K:Ca, K:Ca and K+Mg:Ca ratios. Furthermore, fruits’ weight loss showed a significant positive correlation with potassium content. There was a significant negative correlation between ethylene level and fruit tissue firmness at the end of storage and a positive correlation with N:Ca and N+K:Ca ratios. Cluster analysis divided kiwifruit orchards into two main groups. In conclusion, the results showed that the kiwifruit mineral elements’ content and ratio at harvest time can be used as an effective factor for evaluating post-harvest life of kiwifruits.

Mineral composition in harvested fruits can influenced fruit tissue firmness and postharvest life. In this study fruits were harvested from 70 different commercial kiwifruit orchards on 10 weeks after full bloom and the commercial maturity stage. After harvest, fruit mineral composition such as nitrogen, potassium, phosphorus, calcium, magnesium and dry matter were measured. Tissue firmness was also measured on mature fruits. Thereafter, mature fruits were transferred to storage at 0 ºC and 90-95% relative humidity and after 105 days fruit tissue firmness was evaluated. The regression model showed that, positive correlation existed among fruit tissue firmness at the end of storage with tissue firmness and dry matter of mature fruit at harvest time but a negative correlation with N+K/Ca ratio, phosphor and nitrogen content of mature fruit. Also cluster analysis was divided studied orchards into two main groups. Based on t test fruit tissue firmness at the end of storage in first group orchard was less than second group. In addition, In first group concentration of potassium, phosphorus, nitrogen, N/Ca, N+K/Ca, K/Ca and K+Mg/Ca ratios was higher than the second group, but dry matter in fruitlets and fruits, calcium concentration of mature fruits and fruit tissue firmness at harvest was lower. The discriminate function analysis showed that variables of tissue firmness at the end of storage, ratio of N+K/Ca, K/Ca, N/Ca, K+Mg/Ca had the highest correlation with the discriminant function. In conclusion, mathematical models can be used for prediction of postharvest behavior and storage quality in kiwifruit.

Leaf analysis is a general method of estimating the fertilizer needs in fruit trees، but there exists a limited correlation between it and fruit quality. Throughout the present study، fruits were harvested 10 weeks following full bloom and at the commercial maturity (6. 2 brix) stages from thirteen different commercial kiwifruit orchards that had been fertilized with different fertilizers، the experiment being carried out in the east of Guilan province. Following harvest، such mineral elements as nitrogen، potassium، phosphorus، calcium and magnesium، dry matter and as well fruit tissue firmness (just in second harvest) were assessed. For an evaluation of the storage life، mature fruits were transferred to cold storage of 0 ºC temperature and 90-95% relative humidity، with fruit tissue firmness being evaluated after 105 days past of storage. Results showed significant correlations between fruit tissue firmness (at harvest) and potassium content in fruitlets and between fruit firmness and calcium، nitrogen، as well as dry matter content in mature fruits. There was a significant correlation observed between fruit firmness at the end of storage time and potassium as well as nitrogen content in fruitlets، and also between calcium، nitrogen contents and dry matter in mature fruits. Fruits with higher firmness at harvest time had maintained a higher firmness at the end of their storage period. Also، according to cluster analysis، the kiwifruit orchards were divided into two main groups. It could finally be concluded that the postharvest behavior of kiwifruits can be evaluated through a determination of the mineral compositions of fruitlets and of the mature fruits.