Studies On The Major Characters And Their Influence Factors Of The Rare Purple-Fleshed Sweetpotato [Ipomoea Batatas (L.)Lam.]

The purple-fleshed sweetpotato [Ipomoea batatas (L.) Lam.] have much anthocyanins synthesized and existed in their storage roots with expansive prospects in extracting natural pigment, directly eating as healthful vegetable and processing into functional foods because their anthocyanins have many physiologically hygienic functions derived from their antioxidant activities, such as protecting human-beings from cancers, tumors and cardiovascular disease. However, the purple-fleshed sweetpotato is a rare plant because few resources currently remained. Its benefits are not discovered until recently, which hinders researches and industrialization of them.Based on the introduced purple-fleshed sweetpotato resources from home and abroad, the assessments on the major characters such as yields, anthocyanin content and dry matter content in storage root, eating quality, length of the longest vine, number of base branches, etc, of 24 cultivarities of the purple-fleshed sweetpotato were studied. We further studied the variation laws of anthocyanin contents among these cultivars and during storage root development, the relationships among these variation laws and the major characters, the internal factors which influences eating quality of storage root, and the effects of shading, sort and use level of fertilizer, crossing and selecting on the major characters of the purple-fleshed sweetpotato. The results showed as follows:1. The evaluation and comparison of yields and major characters between 24 purple-fleshed sweetpotato cultivars from Japan and China, and 25 other fleshed sweetpotato cultivars and "Nanshu 88" have been completed in present paper. The results revealed that purple-fleshed sweetpotatoes in general were very poor in fresh storage root yields , in rate of weight 100g and over storage root to weight of total storage root, and in eating quality of storage root, rich in anthocyanin contents, and longer in the length of the longest vine, although had no much difference in vine yields, in contents of dry matter and starch of storage root and in numbers of base branches and roots, compared with those of other fleshed sweetpotatoes. These conclusions would explain why purple-fleshed sweetpotato resources are rare is because the breeders, producers, businessmen pay less attention on them because of their lower yields, worse eating quality and longer vine, and why less progress had made on their industrialization is because of the poor sufficient good raw material supply. So, the purple-fleshed sweetpotato, especially for those cultivars with the lowest yield, would become easily endangered even extinct by natural variation, mixing with other cultivars, virus infection and genetic drift caused by ignoring of storage root selection for the uses of next year.2.The dynamics of 20 kinds of economic traits in 13 purple-fleshed sweetpotato cultivars at 20, 40, 60, 80, 100, 120 and 140 days after their transplanting were investigated, and these traits included the anthocyanin contents, lengths of the longest vine, numbers of base branches, roots numbers, dry matter contents in stem, foliage and roots, fresh and dry yields of roots, fresh and dry yields of stem, fresh and dry yields of foliage, fresh and dry yields of vine, fresh and dry yields of whole plant, and rations of photosynthate to roots, to stem and to foliage.The relationships among variations of the anthocyanin contents and other 19 economic traits were analyzed. The relationships among daily growth rates of the anthocyanin contents and 10 other kinds of yields were also analyzed.During the whole development, the anthocyanin contents present three variation types, i.e., slowly increasing, fluctuating and devious ascending, and had different responses to the growth of length of the longest vine, number of base branches, fresh and dry yields of roots and photosynthate allotments.The anthocyanin contents among 13 cultivars began to have significant difference after 20 days of transplanting, and completed type differentiation during 40-100 days, and had significant negative correlation with the number of base branches, fresh and dry yields of roots, ratio of photosynthate to roots, and had significant positive correlation with dry matter contents of roots, length of the longest vine, fresh and dry yields of stem, dry yield of whole plant and ratio of photosynthate to foliage.Because of the significant negative correlation between daily growth rates of anthocyanin contents and dry matter yields of roots, the anthocyanin accumulation competed with dry matter accumulation for photosynthate in roots. The competitive relation was resolved by different ways in different cultivars.The variation laws of anthocyanin contents and their correlations with the major characters reveal the physiological mechanisms of the lower fresh storage root of the purple-fleshed sweetpotato.3. The results of effects of shading on the fresh yields, anthocyanin contents and yields of storage root of three purpled-fleshed sweetpotato cultivars "Yuzi263", "Yuzi43" and "Yamagawamurasaki" show that shading would result in the decreasing of yields of fresh storage roots, in the increasing of anthocynin contents of storage roots and in decreasing of anthocyanin yields of them because shading decrease the photosynthate amounts and intensify the contradiction between swelling and anthocyanin synthesizing in storage roots. So, in the conservation work of purple-fleshed sweetpotato resources, especially for those cultivares with the lowest yields, and in purple-fleshed sweetpotato production, especially for Sichuan, Chongqing regions with the agricultural cultivation tradition interplanting sweetpotato with corn, the purpled-fleshed sweetpotato cultivars should better be cultivated alone without extensive shading.4. The experiments of effects of the sort and usage of fertilizer on the fresh yields, the anthocyanin contents and yield of storage roots of the purpled-fleshed sweetpotato showed that fertilizer sort would result in the changing of the yields of fresh storage roots, the anthocyanin contents and yields of storage roots depending on fertilizer form and use level. The contradiction between swelling and anthocyanin synthesizing in storage roots can be alleviated by correct sort and use level of fertilizer which can increase the yields of fresh storage roots and anthocyanin, and simultaneously keep the level of anthocyanin contents without siginificant decreasing through influence length of the longest vine, stem width, number of storage root, dry matter in storage root etc.5. The effects of fresh storage roots yields, contents of dry matter, anthocyanin and soluble sugar in storage roots on eating quality of storage roots of 13 purple-fleshed sweetpotato cultivirs were studied in present paper with the help of DPS stepwise regression analysis. The results indicated that the dry matter contents have significant positive correlations with indexes of moisture and texture in eating quality, and anthocyanin contents have significant negative correlations with indexes of moisture and texture, and fresh storage roots yields and soluble sugar contents have no significant correlations with eating quality. Texture and moisture had significant positive correlations with flavor, fiber, general evaluation which influence eating quality. Therefore, the contents of dry matter and anthocyanin in storage roots were major factors that affected the eating quality of storage roots of the purple-fleshed sweetpotato by influence the texture of storage roots. The existence of anthocyanin is major reason that the purple-fleshed sweetpotato has worse eating quality.6. Some cultivars were used in crossing experiments for study on the effects of crossing and selecting on the major characters of the purple-fleshed sweetpotato. The results showed that many purple-flesh sweetpotato lines appeared among offspring population, although these new purple-fleshed sweetpotato lines population still had lower fresh storage root yields, but their lengths and eating quality were obvious improved, and more easily selection could be made because of a wider anthocyanin contents variation range. New purple-fleshed sweetpotato lines with high quality such as higher in fresh storage root yields and anthocyanin contents with good eating quality and shorter vine length could be acquired by correct crossing and selecting.