Changes in Acetylene Reduction Activities and nifH Genes Associated with Field-Grown Sweet Potatoes with Different Nursery Farmers and Cultivars

Kazuhito Itoh,Nao Yakai,Shohei Hayashi,Keisuke Ohashi,Fumihiko Adachi

doi:10.3390/horticulturae5030053

Abstract

Sweet potato cultivars obtained from different nursery farmers were cultivated in an experimental field from seedling-stage to harvest, and the acetylene reduction activity (ARA) of different parts of the plant as well as the nifH genes associated with the sweet potatoes were examined. The relationship between these parameters and the plant weights, nitrogen contents, and natural abundance of 15N was also considered. The highest ARA was detected in the tubers and in September. Fragments of a single type of nitrogenase reductase gene (nifH) were amplified, and most of them had similarities with those of Enterobacteriaceae in γ-Proteobacteria. In sweet potatoes from one nursery farm, Dickeya nifH was predominantly detected in all of the cultivars throughout cultivation. In sweet potatoes from another farm, on the other hand, a transition to Klebsiella and Phytobacter nifH was observed after the seedling stage. The N2-fixing ability contributed to plant growth, and competition occurred between autochthonous and allochthonous bacterial communities in sweet potatoes.

Highlights

The sweet potato (Ipomoea batatas L.) is a dicotyledonous plant that belongs to the familyConvolvulaceae and is a subsistence crop with huge economic importance, especially in developing countries
It is known that the sweet potato grows well in nitrogen-poor infertile soils, and it is believed that this growth ability is partially due to the functions of diazotrophic growth-promoting bacteria that contain endo- and epiphytic microorganisms of this plant [1,2,3]
In a study by Marques et al [10], 17 different genera belonging to α- and γ-Proteobacteria, Actinobacteria, and Firmicutes were isolated from three sweet potato genotypes, with Bacillus strains predominating in two of these genotypes and strains belonging to γ-Proteobacteria predominating in the third

Summary

Introduction

The sweet potato (Ipomoea batatas L.) is a dicotyledonous plant that belongs to the familyConvolvulaceae and is a subsistence crop with huge economic importance, especially in developing countries. Doty [9] identified Enterobacter sp., Rahnella sp., Rhodanobacter sp., Pseudomonas sp., Stenotrophomonas sp., Xanthomonas sp., and Phyllobacterium sp. The plant growth-promoting properties of the above-mentioned isolated endophytes include nitrogen fixation, phytohormone production, siderophore production, antimicrobial activity against phytopathogens, and phosphate solubilization [7,9,10]. In addition to these properties, which have been examined in vitro using artificial media, plant inoculation assays for some of the isolated endophytes indicated that they had the potential to promote plant growth in vivo [8,9]

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Results

Conclusion