Evaluation Of Agronomic And Quality Traits Of 25 Carrot Cultivars

Carrot(Daucus carota ssp.sativus;2n = 2x = 18)is a biennial herbaceous plant with ediable taproot that belongs to genus Daucus of Apiaceae.Carrot is one of the most important root vegetable crops in the world.The taproots of carrots are rich in nutrients,including carotenoids,an important source of provitamin A in the human diet.The carotenoids from carrot are benefical for human health.They could prevent eye diseases such as night blindness,chronic diseases such as cancer,and cardiovascular disease.Carrot breeding started late in China,and the breeding technology was relatively backward.Compared with the United States and some European countries,China were relatively less in the collection and conservation of carrot germplasm resources,which greatly affected the process of carrot breeding.In recent years,the research on carrot germplasm resources mainly focused on studying genetic diversity,molecular markers development,and gene mapping.Scientific and systematic evaluation of carrot agronomic and quality traits is beneficial to the collection,preservation and utilization of carrot germplasm resources.In this study,25 carrot cultivars of different colors that commonly used in the market were selected and planted in Baima Teaching and Scientific Research Base of Nanjing Agricultural University.After the carrots have grown to maturity,their main agronomic and quality traits were analyzed and evaluated by using the methods of difference analysis,correlation analysis,principal component analysis,comprehensive evaluation value analysis,and systematic cluster analysis.This study provides reference information for the selection of carrot cultivars and the breeding of superior cultivars in Nanjing and its surrounding areas,and also provides theoretical reference for the selection of carrot breeding materials in China.The main results of this study are listed as follows:1.Seven agronomic traits of 25 carrot cultivars were measured and analyzed,including root length,root diameter,single root weight,aboveground weight,water content and hardness.Among them,single root weight had the greatest selection potential because it showed the largest the coefficient of variation,reaching up to 47.48%.Single root weight was positively correlated with root length,root diameter,aboveground weight and water content.The results of principal component analysis showed that the cumulative contribution rate of the four comprehensive indicators reached up to 92.856%,which could basically represent the overall information of the main agronomic traits of carrot.The membership function value was used to calculate the comprehensive evaluation value(D value).Among the test carrot cultivars,’San Hong Qi Cun’ showed the highest D value and the best performance.Further systematic cluster analysis of D value showed that the 25 carrot cultivars could be divided into 4 groups at Euclidian distance of 5.The carrot cultivars that belong to group Ⅲ,including ’Da Yu Mei Rei Zhi’,’San Hong Qi Cun’,’Xiao Ding Ba Cun’and ’Shin Kurodagosun’,showed stronger overall,larger root diameter,single root weight,aboveground weight,and larger root-shoot ratio,as well as higher water content than the others.These carrot cultivars showed the best overall performance.2.The contents of carotenoids,soluble sugar,ascorbic acid,and anthocyanins in 25 carrot cultivars were measured and analyzed.The results showed that the content of anthocyanins was significantly different between purple and non-purple carrots,while ’Deep Purple’ carrot showed the highest total content of anthocyanins.The contents of carotenoids in red and orange carrots were much higher than that in purple,yellow,and white carrots,while ’Interceptor’ showed the highest total content of carotenoids.The difference of soluble sugar content among different carrot cultivars was not as great as that of carotenoids,and’San Hong Qi Cun’,’Hong Guan 100’ and ’Purple Sun’ showed the highest sugar content.The difference of ascorbic acid among different carrot cultivars was small.The results of difference analysis showed that the coefficient of variation of anthocyanins was the highest,reaching up to 257.72%.As a result,anthocyanins variation had the highest selection potential,followed by carotenoids.Correlation analysis found that the content of anthocyanins was negatively correlated with carotenoids and ascorbic acid.Among the test carrot cultivars,’Mei Gui Hong’ showed the highest D value and the best performance.Systematic cluster analysis showed that the 25 carrot cultivars were divided into 4 categories at Euclidean distance of 5,among which the group Ⅱ was rich in anthocyanins and the group Ⅲ was rich in carotenoids and soluble sugar.These two groups had better overall performance.