| Pecan(Carya illinoensis)is one of the world’s most famous woody oil trees,and is also a good timber and ecological tree species.In China,with a low self-sufficiency rate of edible oil and an external dependence of 69.9%,as well as a vast territory and abundant mountain resources,the development of pecans and other woody oil crops is of great significance.At present,14 provinces in China have started to introduce the planting of pecans,mainly to produce dried fruits for direct consumption,but as an industry is slow to develop,low yield and low efficiency problems are prominent,the product structure is single.To promote the development of pecan industry,this paper uses 10 asexual lines,including the main cultivar ’Mahan’,as the material to reveal the dynamic changes of main mineral nutrients and nutrient accumulation patterns of pecan during the reproductive period through field trials,to analyze the causes of low yield and low efficiency of pecan from the perspective of mineral nutrition and to establish a nutritional diagnosis method,and to analyze and evaluate the differences between different asexual lines.The study was conducted to analyze the causes of low yield and low efficiency of pecan from the perspective of mineral nutrition and to establish a nutritional diagnosis method.The main results are as follows.(1)The content of eight mineral nutrients of pecan ’Mahan’ showed some regularity with the fertility dynamics,and each element showed its own different or similar characteristics depending on the fruit and leaf parts.Fruit elemental content,most elements(N,P,Ca,Mg,Mn,Zn,and B in the first and middle stages)decreased overall,while K and B differed,with fruit K decreasing first and then increasing,while B increased sharply by 431% at maturity.Leaf element content except N and the early P and K were decreasing,while the rest of the elements(Ca,Mg,Mn,Zn,B)were low before and then high,Ca,Mg,K,P appeared to buckle at the end of fertility especially Ca,Mg buckled tremendously,Mn,Zn,B content dynamics were highly similar.Except for P and K,all leaves were higher than fruits.The specific content of each element and the variation of fertility period are as follows:The range of N content in leaves is 16.35g/kg ～ 24.93g/kg with an average of 20.09g/kg and a CV of 11.22% over the whole growth period;the range of N content in fruits is 6.02g/kg ～29.90g/kg with an average of 11.26g/kg and a CV of 62.41%.The range of P content in leaves is1.07g/kg ～ 3.54g/kg with an average of 1.66g/kg and a CV of 40.72%;the range of P content in fruits is 1.31g/kg ～ 3.99g/kg with an average of 2.26g/kg and a CV of 34.28%.The range of K content in leaves is 6.17g/kg ～ 15.54g/kg with an average of 10.76g/kg and a CV of 20.01%;the range of K content in fruits is 6.11g/kg ～ 18.98g/kg with an average of 14.41g/kg and a CV of25.15%.The range of Ca content in leaves is 14.15g/kg ～ 42.33g/kg with an average of 22.46g/kg and a CV of 27.40%;the range of Ca content in fruits is 4.29g/kg ～ 21.00g/kg with an average of12.01g/kg and a CV of 42.79%.The range of Mg content in leaves is 3.24g/kg ～ 6.50g/kg with an average of 3.85g/kg and a CV of 20.32%;the range of Mg content in fruits is 0.92g/kg ～ 4.80g/kg with an average of 2.45g/kg and a CV of 50.28%.The range of Mn content in leaves is 0.72g/kg ～1.54g/kg with an average of 1.18g/kg and a CV of 21.57%;the range of Mn content in fruits is0.12g/kg ～ 0.89g/kg with an average of 0.42g/kg and a CV of 53.48%.The range of Zn content in leaves is 63.40mg/kg ～ 104.4mg/kg mg/kg and a CV of 14.51%;the range of Zn content in fruits is26.33mg/kg ～ 85.15mg/kg with an average of 41.66mg/kg and a CV of 43.57%.The range of B content in leaves is 20.75mg/kg ～ 59.03mg/kg with an average of 43.33mg/kg and a CV of 32.00%;the range of B content in fruits is 11.40mg/kg ～ 60.60mg/kg with an average of 22.68mg/kg and a CV of 60.52%.The average content of elements during the growth period is ranked: leaf Ca > N > K > Mg >P > Mn > Zn > B,fruit K > Ca > N > Mg > P > Mn > Zn > B.Among them,Ca > N,Mg > P,Mn near P(leaf Mn even higher than the conventional medium element of 0.1%),which is special compared with conventional crops.Therefore,these characteristics of pecans may be the peculiarities of their phytonutrition that distinguish them from other crops.(2)The cumulative accumulation of the mineral elements in pecan ’Mahan’ fruit showed an overall increasing trend,similar to the trend of the accumulation of biomass,and showed more obvious stage characteristics.The accumulation increased slowly from early to mid-July;from mid-late July to mid-August,each element accumulated rapidly to the fruit,and the contribution rate even exceeded 100%;from late August to late September,the changes leveled off,and P,Ca,Mg and Mn even appeared to accumulate negatively in September,showing a net transfer from the fruit to the outside;at the end,they accumulated positively again.The magnitude of the accumulation of mineral elements was B > K > Zn > N > Ca > P > Mg > Mn.(3)In comparison with the conventional(high-yielding)stand of pecan ’Mahan’,the main mineral elements contents of leaves,fruits,and annual branches of ’Mahan’ low-efficiency stand in July and September were highly consistent.The contents of N,P,K,Mn and Zn in the same parts were lower in the low-efficiency forest than in the conventional forest,while the contents of Ca and Mg were higher in the low-efficiency forest than in the conventional forest,especially in the leaves,which were more significant than in the other parts,and the leaf N,P,K,Mn and Zn were highly significant in July and September,and the bast and xylem N,P and Zn were also highly significant in September.Mn,Zn,etc.were also very significantly lower in the low-efficiency forest than in the conventional forest.Accordingly,the deficiency of mineral nutrients N,P,K,Mn,and Zn may constitute the cause of the inefficient forest.This difference in mineral matter between stands is not consistent with the effective nutrient content(supply)of the soil,except for P,which is even the opposite,and the reasons for which need to be further revealed.Based on the comprehensive nutrient diagnosis DRIS index,the relative nutrient deficiency order of the inefficient forest was inferred as follows: leaf K > Mn > P > Zn > N > B > Mg > Ca in July,fruit P > K > Mn > N > Zn > B > Mg > Ca in July,leaf P > K > Mn > Zn > N > B > Mg > Ca in September,and fruit P > Mn > N > Zn > B > Mg > Ca > K in September.The indices of P,Mn,K,N,and Zn for leaves and fruits in July and September were negative(all highly consistent except for K for fruits in September),and the insufficient supply of these elements and deviation from equilibrium may be the cause of inefficient forest,especially P and Mn are far from equilibrium and must be supplemented.The DRIS diagnostic conclusion is consistent with the content comparison diagnostic conclusion.(4)The results of fruit traits analysis of 10 lines of pecan showed that,in terms of fruit quality and appearance,green fruit weight,nut weight,kernel weight,seed rate,kernel rate,green fruit length,green fruit width,nut length,and nut width,were significantly different among the 10 lines of pecan,and only nut shell thickness did not show significant differences.Among the 10 lines,the coefficients of variation of each index were kernel weight > nut weight alone > green fruit weight alone > seed yield > nut shell thickness > nut width > kernel yield > nut length > green fruit length > green fruit width.Among the nutrients contained in the seed kernels,protein,soluble sugar and tannin differed somewhat significantly among the 10 lines,and crude fat did not differ significantly;the average crude fat content of the 10 lines was 70.01%,the average protein content was 67.50 mg/g,the average soluble sugar content was 10.7 mg/g,and the average tannin content was 6.07 mg/g.The coefficients of variation of each index was soluble sugar > tannin > protein >crude fat.All the lines,especially No.28,No.104 and No.34,can be used for edible oil production;No.104 and No.28 can be recommended as fruit cultivars;No.1,No.35,No.28,No.34 and No.29 can be high-grade edible oil varieties;No.29,No.21,No.20 and No.34 can be developed and utilized as fresh food varieties.In addition,the average oil rate of pecan nuts is 35.36%(seed rate ×crude fat content).Combined with the lack of arable land resources in China and the vast area of mountainous regions,the development of pecan industry is very promising to make up for the shortage of edible vegetable oil in China.(5)The fatty acid composition of the seeds of the 10 lines of pecan showed that the contents of palmitic acid,stearic acid,arachidonic acid,oleic acid,linoleic acid and linolenic acid were significantly different among the 10 lines of pecan,and only cis-11-eicosanoic acid was not significantly different.The average content of fatty acid components in the order of oleic acid(70.02%)> linoleic acid(19.58%)> palmitic acid(5.73%)> stearic acid(2.38%)> linolenic acid(0.97%)> cis-11-eicosanoic acid(0.25%)> arachidic acid(0.05%).Unsaturated fatty acids(average content 91.82%)dominate,with monounsaturated fatty acids accounting for 71.26% and polyunsaturated fatty acids accounting for 20.56%;oleic acid is the predominant monounsaturated fatty acid,followed by cis-11-eicosatrienoic acid;linoleic acid is the predominant polyunsaturated fatty acid,followed by linolenic acid.The average content of saturated fatty acids is 8.17%,palmitic acid is the main saturated fatty acid,followed by stearic acid and again arachidic acid.Unsaturated fatty acids are 11.24 times more than saturated fatty acids,and monounsaturated fatty acids are 3.47 times more than polyunsaturated fatty acids.Pecan oil has the characteristics of "low saturated fatty acids and high unsaturated fatty acids" of healthy and high-quality edible oil,and has great development and market potential as a high-quality edible oil resource. |
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