Fruit quality of Rosa sterilis planted in different regions of Guizhou province, China

Abstract:【Objective】Rosa sterilis is regarded as a new fruit species that is widely cultivated in Guizhou.It is regarded as a natural wild fruit, which grows at altitudes from 500 to 2 500 meters in the sunny slopesand valleys, along roadsides, and in the bushes. Due to the obvious distinctions in fruit quality caused bydifferent planting conditions, this paper aims to evaluate the fruit quality of R. sterilis in diverse areas toprovide a scientific basis for development of R. sterilis industry in Karst areas and offer theoretical founda-tion for ecological regionalization of R. sterilis.【Methods】R. sterilis fruits from 14 different towns of Gui-zhou province were investigated. 10 main quality parameters were measured, including fruit shape index,single fruit mass, dry matter, edible rate, soluble solid content, soluble proteins, soluble sugars, titratableacids, ratio of soluble solids to titratable acids and ratio of soluble sugars to titratable acids. The parame-ters of appearance quality collected included fruit weight, fruit longitudinal diameter, transverse diameter,fruit shape index, fruit number per branch, etc. Fruit longitudinal and transverse diameters were measuredby a Vernier caliper. The fruit shape index was the ratio of fruit longitudinal diameter to transverse diame-ter. The weight of fruit was determined by an electronic balance. The intrinsic quality of R. sterilis was reflected by fruit flavor and nutritional values, which included sugar to acid ratio, total soluble solid to titratable acid ratio, edible rate, soluble sugars, soluble solids, dry matter, soluble proteins, single fruit mass and titratable acids. Soluble solids, total soluble sugars, titratable acids, soluble proteins, dry matter, and edible rate were determined by Abbe refractometer, phenol sulfuric acid method, Na OH neutralization titration method, coomassie brilliant blue method, drying method and weighing method, respectively. Fruit flavor was scored by an evaluation team consisting of 10 people. The evaluation utilized a 5-grade marking system, denoted by Gi(i means the score of R. sterilis' fruit evaluation is from the number of“i”planting site), which was ranked by 5 with agreeable sour-sweet taste and superior aroma intensity, 4 with moderately agreeable sour-sweet taste and good aroma intensity, 3 with mild sour or sweet taste and aroma intensity, 2 with slight sour-sweet taste and little aroma intensity, and 1 with plain taste and no aroma. The method of membership function was used to normalize the raw data. According to the first formula, positive correlation indicators for fruit quality assessment were sugar-acid ratio, total soluble solids to titratable acids ratio, edible rate, soluble sugars, soluble solids, dry matter, soluble proteins, fruit shape index,and single fruit mass. The second formula was applied to titratable acid content, which was a negative correlation indicator. The third formula was Euclidean distance, which could reduce the dimension of data from 10 to 1. The results showed that Yi, which was a comprehensive evaluation of R. sterilis fruit from different planting sites. Principal component analysis(PCA) was used to identify interrelations between the quality indicators of R. sterilis. In order to eliminate the correlation between indicators and reduce the redundancy of data processing, it was essential to select representative indicators. Therefore, comprehensive evaluation indicators of R. sterilis were calculated using the normalization method and an Euclidean distance of 10 for individual indicators. And the comprehensive evaluations of R. sterilis were assessed by principal component analysis, stepwise regression analysis and K-means.【Results】The raw data of 10 individual indicators from 14 planting sites were normalized for correlation analysis. The results showed that10 individual quality indicators of R. sterilis were closely related. Soluble solid content and dry matter, soluble proteins and fruit shape index, soluble sugars and edible rate, soluble sugars and soluble solids, sugar to acid ratio and soluble sugars, and sugar to acid ratio and total soluble solid to titratable acid ratio were shown to have significant positive correlations. Titratable acids and fruit shape index had a significant negative correlation(p<0.05). Total soluble solid to titratable acid ratio and titratable acid, sugar to acid ratio and total soluble solid to titratable acid ratio, sugar to acid ratio and total soluble solid to titratable acid ratio had significant positive correlations(p<0.01). And principal component analysis was applied to select four irrelevant principal components(F1-F4), which covered most information of the R.sterilis. The stepwise regression analysis was used to remove the main component factors contributing to the comprehensive evaluation index. Finally, the fourth principal component persisted. The 10 indicators in sequence were sugar toacid ratio, total soluble solid to titratable acid ratio, edible rate, soluble sugars,titratable acids, soluble solids, dry matter, soluble proteins, fruit shape index, and single fruit mass, and the front four indicators contributed most to comprehensive evaluation of R. sterilis fruit. Then, the Kmeans cluster analysis of the R. sterilis quality comprehensive evaluations in 14 planting sites was utilized to divide all regions into 4 types: excellent, good, general and poor.【Conclusion】This research revealed that the internal quality has great significance in the evaluation of R. sterilis, and the evaluation methods were objective and reasonable, which revealed the diversity of the fruit quality in R. sterilis from different planting areas. Those results will guide ecological regionalization research of R. sterilis quality in Guizhouprovince.