Phytophthora sojae zoospores differ in chemotaxis to the root and root exudates of host soybean and nonhost common bean
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Phytophthora root and stem rot of soybean is a destructive disease in many countries caused by the soil-borne pathogen Phytophthora sojae. The interaction between soil-borne pathogens and plant roots before invasion is a focus of interest for revealing host and nonhost resistance mechanisms to soil-borne pathogens. In the present study, soybean cvs. Sloan (susceptible), Williams 82 (resistant) and nonhost common bean cv. Yidianhong were used to determine the effect of roots, root exudates, and isoflavones, amino acids, sugars, and citric acid from the root exudates on the pre-infection behavior (taxis, encystment and cyst germination) of zoospores of P. sojae. The elongation zone of roots of both host soybeans attracted significantly more zoospores than did that of the nonhost bean, and that of the susceptible cultivar attracted significantly more zoospores than did that of the resistant cultivar. Similarly, the host soybean root exudates attracted zoospores and promoted zoospore encystment and cyst germination, but nonhost root exudates had no effect on zoospores. Thus, P. sojae apparently selects its host depending on the root exudates. Of the 26 total components detected from root exudates, the exudates from susceptible and resistant soybeans and nonhost common bean had 12, 17, and 25 components respectively. The differences between the host and nonhost were mainly in the type and concentration of amino acids. Most components were significant chemoattractants of P. sojae zoospores. However, when these attractants were mixed at their relative concentrations in the root exudates, the chemoattraction was significantly reduced compared to that of the sum of each components, and the reduction from strongest to weakest was nonhost common bean, resistant and susceptible soybeans, indicating that these components in the root exudates interact with each other, and the intensity of the interaction relates to the type and concentration of the components. This phenomenon is because some components may share the same receptor, thus causing an obstructive effect. This result may also be a reason that common bean is a nonhost of P. sojae. In addition, the relative local concentrations of citric acid in the root exudates of both nonhost cv. Yidianhong and resistant cv. Williams 82 were repellent to zoospores of P. sojae. Root exudates of susceptible cv. Sloan amended with two concentrations of citric acids especially reduced zoospore chemoattraction, indicating that citric acid in the root exudates also plays an important role in host and nonhost resistance to P. sojae.
KeywordsPhytophthora sojae Chemotaxis Root exudates Host soybean Nonhost common bean
This research was supported by the National Natural Science Foundation of China (grant nos. 31670444, 31370449).
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Conflict of interest
The authors declare that they have no conflict of interest.
Human participants or animals
This article does not contain any studies with human participants or animals performed by any of the authors.
- Dong Y, Dong K, Zheng Y, Yang Z, Tang L, Xiao J (2014) Allelopathic effects and components analysis of root exudates of faba bean cultivars with different degrees of resistance to Fusarium oxysporum (in Chinese with English summary). Chin. J Eco-Agr 22:292–299Google Scholar
- Hao WY, Ran W, Shen QR, Ren LX (2010) Effects of root exudates from watermelon, rice plants and phenolic acids on Fusarium oxysporum f. sp. niveum (in Chinese with English summary). Sci Agric Sin 43:2443–2452Google Scholar
- Huang WB, Ma R, Yang D, Liu XP, Song JF (2014) Organic acids secreted from plant roots under soil stress and their effects on ecological adaptability of plants. Agric Sci Technol 15:1167–1173Google Scholar
- Riggs K (2010) Chemotaxis of Phytophthora sojae zoospores to soybean roots is altered by isoflavone silencing. Honors thesis, Ohio State University, Columbus, OH, USAGoogle Scholar
- Schmitthenner AF, Bhat RG (1994) Useful methods for studying Phytophthora in the laboratory. Special circular 143. Ohio Agricultural Research Development Center, WoosterGoogle Scholar
- Uren NC (2000) Types, amounts, and possible functions of compounds released into the rhizosphere by soil-grown plants. In: Pinton R, Varanini Z, Nannipieri P (eds) The rhizosphere: biochemistry and organic substances at the soil–plant interface. Marcel Dekker, New York, pp 19–40Google Scholar
- Wang JY, Lv YY, Yu D, Zhang WN, Pu FZ, Shen SS (2014) Effects of root exudates from different resistant pepper varieties on Phytophthora capsici (in Chinese with English summary). China Vegetables 1:13–16Google Scholar
- Xu BH, Xie LX, Zhang LY (2014) Advanced in group irritability phenomenon in fungi (in Chinese with English summary). J Microbiol 34:100–105Google Scholar
- Zhang XB, Wu Y, Lin H (2006) Study on method of hydrolyze isoflavone in soybean by HPLC (in Chinese with English summary). Cereals Oils 4:19–21Google Scholar
- Zhang L, Fang Y, Ji S, Jiao Y, Liao J, Li J, Deng W, Zhu S, Yin J, Yang M (2015) Inhibitory activity of maize root exudates against Phytophthora nicotianae and antifungal compounds analysis (in Chinese with English summary). Chinese J Biol Control 31:115–122Google Scholar