Study on Arbuscular Mycorrhizal Fungi (AMF) Inoculation on the Growth and Development, Tuber Weight, Allantoin Content and Antioxidant Ability in Yam (Dioscorea alata L.) Cultivated in Taiwan

• Main Authors: Lu, Fun-Chi, 呂芳舉
• Other Authors: Yan, Chang-Rui
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/98230614425969659146

博士 === 國立屏東科技大學 === 農園生產系所 === 104 === The symbiotic association between arbuscular mycorrhizal fungi (AMF) and the roots of plants is widespread in the natural environment. AMF benefit their host plant principally by increasing the uptake of macronutrients and some micronutrients, resistance to soil pathogens, tolerance to salinity, heavy metals, and drought stress; maintenance of soil aggregate stability and influence the secondary metabolism levels of plants. The yam (Dioscorea spp.) tubers are edible, medicinal, and used as health foods, they have received considerable attention among the medicinal plants. Yam tubers can produce considerable amounts of antioxidant namely, polyphenols, flavonoids and anthocyanins. They also contained high levels of allantoin that is playing an important role in present skin inflammation and ulcers of the human body; thus, the secondary metabolites that exist in yam tubers have value for development and utilization in medicine practice and health care. In this study, five commercial species and line of yams (Dioscorea alata L.) were inoculated with six species of AMF, Glomus clarum, G. etunicatum, G. fasciculatum, Gigaspora sp., G. mosseae, and Acaulospora sp., in field cultivation conditions to investigate the influence of AMF inoculation on mycorrhizae formation rates, physiological components of leaves, nutrition analysis, tuber weights, secondary metabolite content and antioxidant ability in yam tubers. The results showed that all six AMF species were able to form mycorrhizae relationship with the host yams, and mycorrhizae formation rates ranged from 63.33% to 90%, indicating that these AMF present high compatibility with the host yams. In this research, the majority of the yam plants with AMF inoculation had substantially higher chlorophyll content as well as soluble carbohydrate and protein compared with those non-inoculation control group. The amount of chlorophyll content in yam leaves inoculated with AMF the control group were 1.93/1.73, 2.30 /2.10, 2.12/1.86, 1.93/1.62 and 1.93 /1.66 mg/g for Tainung No. 1, Tainung No. 2, Zihyuxieshu , Ercih and Tainung No. 5 respectively; and the maximum increased amount of both the soluble protein and carbohydrate were 76.55/60.83, 98.99/73.70, 147.33/120.80, 74.06/51.37 and 92.91/ 59.41 mg/g; 140.75/105.75, 104.62/81.73, 129.88/103.54, 158.13/110.28 and 157.90/134.27 mg/g respectively. The root colonization by AMF enabled the leaves of host yam presented high concentrations of nitrogen and potassium than those of the controls. However, yams inoculated with six of AMF for six weeks did not increase the content of soluble phosphorus. Our study showed that AMF inoculation can improve the tuber weights of five yams. G. etunicatum inoculation treatment increased the yam tuber weights by 39%, 35%, 20%, 56%, and 40% for Tainung No. 1, Tainung No. 2, Ercih, Zihyuxieshu, and Tainung No. 5 compared with the control group, respectively. The content of secondary metabolites, such as polyphenols, flavonoids, and anthocyanin, was significantly increased by the AMF treatment in tuber flesh and peel of the tested yam. Specifically, the maximums exchange of secondary metabolite contents increased to 40%, 42%, and 106% for polyphenols, flavonoids and anthocyanin respectively in the tuber fresh. Moreover, those ample functional ingredients, involving polyphenols, flavonoids and anthocyanins can be extracted from the peel of tuber, thereby increasing the potency and utilization of yam tubers. The AMF inoculation boost the secondary metabolites antioxidant compounds, thus enhancing the antioxidant ability of yams. The allantoin analysis experiments showed that the yam tuber peels was with higher allantoin content than the yam tuber flesh. The peels of per gram of tuber are 159%, 209%, 64%, 99% and 97% higher than those of the fresh of Tainung No. 1, Tainung No. 2, Ercih, Zihyuxieshu, and Tainung No. 5, respectively. Compared with the non-inoculated yams, the allantoin levels in tubers presented that in both the fresh and peels were 10.7%, 8.3%, 7.6%, 3.2% and 12.3%; 15.4%, 18.0%, 15.2%, 4.0% and 22.5% for Tainung No. 1, Tainung No. 2, Ercih, Zihyuxieshu, and Tainung No. 5 respectively. In this study, the data showed that Tainung No. 1, Tainung No. 2 and Ercih three white flesh yams species treated with G. etunicatum and G. mosseae enhanced the yam tuber yield and polyphenols and flavonoids content. The two species of purple yams, Zihyuxieshu and Tainung No. 5, treated with G. etunicatum and Gigaspora sp. enhance the yam tuber yield and polyphenols, flavonoids and anthocyanins content. The inoculation of yams with AMF can expedite plant growth and increase the tuber weight, antioxidants, allantoin content of secondary metabolites in tubers. Therefore, AMF can be used as a microbial fertilizer and developed for yam cultivation and production.