| Litsea mollis Hemsl.is a perennial deciduous shrub or small tree of the genus Litsea Lam.in the Lauraceae family,and the whole plant contains essential oil,which is the main raw material for the production of Litsea cubeba oil,its fruit is the main oil producing part and has high economic,edible and medicinal values.However,the existing wild resources are the main resources in China,and the yield is low and scattered.There are few improved varieties of artificial selection.At present,there has not been a large-scale plantation of L.mollis.Therefore,it is of great theoretical significance and practical value to the research on seed selection and resource exploitation and utilization.In this paper,the fruit drop rate statistics and morphological research were carried out in different maturity stages to explore the change rule of fruit growth and development in the experiment base of L.mollis from Shuangfeng Town,Hechuan District,Chongqing;the essential oil was extracted by steam distillation,and the volatile components of essential oil were detected by GC-MS for qualitative and quantitative analysis.The composition and content differences of volatile components of essential oil in different maturity stages were determined.Finally,principal component analysis（PCA）was used to select superior individual plant.The main results are as follows:（1）Analysis of fruit drop of different maturity stages of L.mollis:The results showed that the variation trend of fruit drop rate in different maturity stages showed an irregular"S"curve.There were two peak periods of fruit dropping during the whole fruit development period,the first occurred from early April to mid-May,which was physiological fruit dropping stage,and the second occurred from mid-July to late July,which was mature fruit dropping stage.At the same time,the fruit drop rate of early maturity was compared with that of late maturity.The results showed that the fruit drop rate of late maturity was higher than that of early maturity in physiological fruit drop stage,but in the mature fruit dropping stage,the fruit drop rate of late maturity was significantly lower than the early maturity,and early maturity was 14～21d earlier than late maturity into the mature fruit dropping stage.In conclusion,control of physiological fruit loss is the key to plant high yield,for early maturity,the key to ensure high yield is to pick the fruit before ripening and fruit setting.Therefore,in order to ensure the plant yield and fruit quality,the physiological amount of fruit loss should be controlled first,and then the fruit should be picked before the arrival of the mature fruit loss period,that is,the early maturity of the fruit should be picked in mid-July,and the late maturity of the fruit should be picked in late July.（2）Analysis of the fruit growth and development pattern of different maturity stages of L.mollis:The variation trends of fruit weight,fruit shape and peel thickness were similar in different maturity stages,except for fruit shape index,which showed different degree of"S"curve.Early fruit development,the early skin is yellow,the late skin is green,with fruit growing and fruit organization gradually hardening,the skin surface are white spots,from fruit color is changed from dark green to red and the top to the base color becomes shallow gradually,and early mature later than early14～21d turn into color stage,mature skin become bright,soften skin tissue,the fruit all turns red or purple black.According to the three kinds of fruit traits,combined with the color changes during fruit growth and development,the fruit development process can be roughly divided into four stages.Fruit expansion stage（S1～S3）,fruit rapid growth stage（S3～S4）,fruit slow growth stage（early maturity S4～S11 and late maturity S4～S13）and fruit maturity stage（early maturity S11～S14 and late maturity S13～S14）.（3）Analysis of essential oil yield,volatile composition and content of different maturity stages of L.mollis fruits:Steam distillation was used to extract the essential oil from the fruits of L.mollis at different maturity stages.The results showed that the yield of essential oil from early maturing fruit was Y16（4.880%）>Y14（4.544%）>Y18（3.660%）>Y5（3.601%）>Y13（3.334%）>Y1（3.139%）>Y19（2.814%）>Y2（2.326%）;the yield of essential oil from high to low was Y9（4.527%）>Y20（4.347%）>Y11（4.108%）>Y17（3.600%）>Y8（3.519%）>Y12（2.722%）>Y21（2.521%）>Y10（2.326%）.The volatile components of the essential oil of the fruits of L.mollis at different maturity stages were determined by GC-MS,the qualitative results showed that there were significant differences in the components of volatile components in fruit essential oils at different maturity stages,forty-nine volatile components were identified at early maturity,including 25 olefins,11 alcohols,6 esters,3 ketones and 4 aldehydes.A total of 56 volatile components were identified at late maturity,including 28 alkenes,13 alcohols,7 esters,3 ketones and 5 aldehydes.The quantitative results showed that the contents of volatile components in essential oil of L.mollis fruits at different maturity stages were significantly different,aldehydes（early maturity:65.01%～92.01%;late maturity:59.07%～72.07%）accounted for the highest proportion of olefin（early maturity:5.94%～25.00%;late maturity:16.26%～28.98%）,alcohols（early maturity:1.47%～11.00%;late maturity:5.50%～11.90%）followed by ketones（early maturity:0.37%～2.79%;late maturity:1.70%～3.23%）and esters（early maturity:0.22%～2.61%;late maturity:0.41%～4.00%）,in which citral was the main volatile component（early maturity:62.47%～91.43%;late maturity:56.24%～70.46%）.Based on the results of volatile components in different maturity stages,14common volatile components and 18 unique volatile components were screened.There were 14common volatile components including 5 olefins and 4 alcohols.1 ester,1 ketone,3 aldehydes;The18 unique volatile components included 9 alkenes,5 alcohols,1 ester,2 ketones and 1 aldehyde.（4）Superior individual plant selection of L.mollis at different maturity stages:In the selection of superior individual plants,both economic and growth traits should be considered.According to the analysis of phenotypic variation of fruit characters,the variation coefficient of early maturity was2.154%～81.818%,and that of late maturity was 2.180%～68.750%.The degree of variation was relatively large,indicating that there were significant differences among superior plants at different maturity stages and they had great selection potential.Principal component analysis（PCA）was used to select the best individual plant in different ripening stages.The Z（EM）values of early maturing fruit quality index from high to low ranked as Y5（1.983）>Y1（1.252）>Y14（1.083）>Y13（-0.010）>Y2（-0.279）>Y18（-0.503）>Y19（-0.883）>Y16（-0.263）.The comprehensive score of late fruit quality index Z（LM）ranked from high to low as Y20（1.632）>Y17（1.422）>Y8（1.208）>Y11（1.010）>Y9（0.931）>Y21（-1.552）>Y12（-1.723）>Y10（-2.928）.The overall score was positive and the highest was superior single plant,that is,2 superior single plants（Y5 and Y1）were screened out for early maturity,and 2 superior single plants（Y20 and Y17）were screened out for late maturity. |
