Fruit Growth And Development Regularity And Comprehensive Evaluation Of Four Carya Illinoensis Varieties In Hunan Province

Carya illinoensis is a famous dried fruit tree species of Carya genus in Juglandaceae,also known as "pecan",etc.It is one of the most rapidly developing economic tree species in China at present.In this research,the widely planted pecan varieties ’Pawnee’,’Mahan’,’Pyzner’ and ’Weston’with different maturity stages were used as research materials,and the dynamic changes of fruit appearance and content were measured during the fruit growth and development,and the economic characters of these four varieties were comprehensively evaluated by the method of principal component analysis,in order to provide a basis for variety selection and timely harvest of C illinoensis in Hunan Province.The results are as follows:(1)The fruit growth of four C illinoensis varieties showed an ’S’growth curve.August 20th to September 10th is the period of rapid growth of fruit transverse diameter,and July 20th to August 20th is the period of rapid growth of fruit longitudinal diameter.The dry and fresh weight of the fruit and seed of four varieties accumulated with time,and the two varieties’Pawnee’ and ’Mahan’ were significantly higher than the others.The variety’Mahan’ with the highest kernel weight and kernel rate reached 64.26%,and the kernel rate of ’Pawnee’ reached 60.54%.There was no significant difference of the thickness of pericarp and seed coat among the four varieties.Correlation analysis of fruit appearance traits of C illinoensis showed that longitudinal diameter was significantly correlated with seed shell thickness,kernel weight and kernel rate.Fresh fruit weight was significantly correlated with fruit dry weight.Kernel weight was negatively correlated with shell thickness.(2)The oil accumulation in the seed kernel of four varieties occurred after July 20th.Oil content of ’Pawnee’ was the highest,reached 60.34%.The fatty acid composition showed the fastest growth period of oleic acid from August 20th to September 30th.Palmitic acid was abundant in the early and middle stages of oil synthesis,and the range of change in the later stage was more than 20%.With the growth and development of the fruit,the content of soluble sugar and starch decreased at first and then increased.The content of soluble protein generally showed an upward trend,with a rapid growth period from July 20th to September 10th.The fruit moisture content of four C illinoensis varieties showed a downward trend in the whole development period,with the range of 75.68%-60.83%.Correlation analysis showed that unsaturated fatty acid was significantly correlated with fruit moisture content.Soluble protein content was significantly correlated with soluble sugar content.Phosphorus and potassium content of fruit increased steadily,while the content of nitrogen decreased first and then increased.During the whole fruit development period,Zn showed a steady upward trend;Fe accumulated rapidly in the late fruit development period;the content of Mn increased first and then decreased.Correlation analysis shows that Fe and Mn content were positively correlated.(3)Three-year average nut yields of four C illinoensis varieties ranged from 3.69 to 7.15 kg/plant,and all of them had the highest yields in 2020.There were significant differences of the yield among varieties,the yield of’Pawnee’ was the highest.Comprehensive evaluation was made on all the economic indicators of four C illinoensis,and the scoring order is’Pawnee’>’Mahan’>’Pyzner’>’Weston’.The earliest harvest time of the four varieties is ’Pyzner’ and the latest is ’Mahan’.