Effect Of Harvesting Time On Walnut Fruit Quality Of Xin Jiang J.regia ’Wen 185’ And J.regia ’XinXin 2’

Based on the problem of the quality decline of walnut(Juglans regia)and kernels caused by early and late harvesting during the production of walnut in different regions of Xinjiang,two main varieties of Juglans regia‘Wen 185’ and Juglans regia ‘Xinxin 2’ from Wensu County(Garden A)in Aksu prefecture and Yecheng County(Garden B)in Kashgar Prefecture were selected as the research objects.The changes of walnut fruit appearance quality and kernel intrinsic quality were measured with seven harvesting time set,and the differences of walnut fruit quality in different harvesting time were compared.Besides,the fruit quality was evaluated by principal component analysis.By analyzing the relationship between the cracking rate of green walnut fruit quality,the best harvesting period of two main varieties of walnut in different producing areas was determined.The main conclusions are as follows:(1)With the delay of harvesting time,the mean value of three diameters of fresh walnut fruits,the mean value of three diameters of walnut,the single weight of nuts,the rate of grain yield and the rate of diameter kernels of Juglans regia ‘Wen 185’ and Juglans regia ‘Xinxin 2’ varieties of walnut in Garden A and B all showed a rapid,slow and then steady increase upward trend,and reached the peak value in harvesting period Ⅶ.As the walnut ripened,the green walnut cracked and lost water.The single weight,water content and shell thickness of fresh fruits were decreased gradually.With the delay of harvest,fruits of Juglans regia ‘Wen 185’ and Juglans regia‘Xinxin 2’ varieties of walnut in Garden A and B were gradually ripening.The color of the involucre gradually was changed from dark green to yellowish green,and the villi on the surface of the involucre was gradually decreased.The phenomenon of green fruit cracking appeared in walnuts since harvesting period Ⅶ.With the increase of maturity,the cracking rate of green walnut on the whole tree was also increased.The involucre became easy to peel,the residual involucre on the shell surface was less,and the black spot rate of the shell was declined gradually.As the walnut gradually tended to mature,the nutrients in the fruits were accumulated and transformed,the kernel color was gradually changed from light white to yellow,the seed coat color was gradually changed from bright white yellow to yellow white or light yellow brown,and the kernel also tended to be full.(2)During the harvesting period Ⅰto Ⅵ,namely the key period of fruit fat accumulation,the fat content of kernels of Juglans regia ‘Wen 185’ and Juglans regia ‘Xinxin 2’ varieties of walnuts in Garden A and B was increased rapidly,meanwhile,protein and vitamin also expressed a trend of gradual increase and reached the peak at harvesting period Ⅶ.Tannin,P,Na and Fe showed no obvious change.K and Ca were decreased firstly and then increased prominently,Zn was increased gradually,and they all reached the peak value at harvesting periodⅦ.The total contents of the five amino acids showed an overall trend of first rising trend and then downtrend,and all reached the peak value in the harvest stage Ⅵ.(3)For Juglans regia ‘Wen 185’ and Juglans regia ‘Xinxin 2’ varieties of walnuts in Garden A and B,with the increase of the cracking rate of green walnut,the mean value of the three diameters of fresh walnuts,the mean value of the three diameters of nuts and the single weight of nuts were increased,and the contents of fat,protein,vitamin C,vitamin E,mineral elements and amino acids were also increased,while the shell thickness,water content and black spot rate were decreased.The greater the cracking rate of green walnut was,the more the fruit size and internal nutrients were increased with fruit ripening.The results demonstrated that the cracking rate of green walnut can be applied as a critical basis for judging the suitable harvesting period of walnuts.It was determined that the comprehensive evaluation scores of Juglans regia ‘Wen 185’ and Juglans regia ‘Xinxin 2’varieties of walnuts in Garden A were the highest in the harvesting period Ⅵ,(September 4,October 5),while the comprehensive evaluation scores of Juglans regia ‘Wen 185’ and Juglans regia ‘Xinxin 2’ varieties of walnuts in Garden B were the highest in the harvesting period Ⅶ(September 4,September 24).Therefore,it was concluded that Juglans regia ‘Wen 185’ and Juglans regia ‘Xinxin 2’ varieties of walnuts in Garden A begin to enter the appropriate harvesting period when the cracking rate of green walnut reaches about 65%(September 4,October 5),while Juglans regia ‘Wen 185’ and Juglans regia ‘Xinxin 2’ varieties of walnuts in Garden B start to enter the appropriate harvesting time when the cracking rate of green walnut reaches about 75%(September 4,September24).