Abstract
Sweet potato (Ipomoea batatas L.) grows well even in infertile and nitrogen-limited fields, and endophytic bacterial communities have been proposed to be responsible for this ability. Plant-growth-promoting bacteria are considered eco-friendly and are used in agriculture, but their application can interact with endophytic communities in many ways. In this study, a commercial biofertilizer, OYK, consisting of a Bacillus sp., was applied to two cultivars of sweet potato, and the effects on indigenous endophytic bacterial communities in field conditions were examined. A total of 101 bacteria belonging to 25 genera in 9 classes were isolated. Although the inoculated OYK was not detected and significant plant-growth-promoting effects were not observed, the inoculation changed the endophytic bacterial composition, and the changes differed between the cultivars, as follows: Novosphingobium in α-Proteobacteria was dominant; it remained dominant in Beniharuka after the inoculation of OYK, while it disappeared in Beniazuma, with an increase in Sphingomonas and Sphingobium in α-Proteobacteria as well as Chryseobacterium and Acinetobacter in Flavobacteria. The behavior of Bacilli and Actinobacteria also differed between the cultivars. The Shannon diversity index (H) increased after inoculation in all conditions, and the values were similar between the cultivars. Competition of the inoculant with indigenous rhizobacteria and endophytes may determine the fates of the inoculant and the endophytic community.
Highlights
Modern agriculture systems are being intensified through the use of various technologies to achieve maximum efficiency and high qualify products to meet the growing global demand for food supply [1]
It is well-known for its ability to grow well even in infertile and nitrogen-limited fields [11,12], and nitrogen fixation by endophytic bacteria has been proposed to contribute to this attribute [13]
We examined culturable endophytic communities at harvest in order to obtain further information on the effects of Plant-growth-promoting rhizobacteria (PGPR) inoculation on indigenous endophytic bacterial communities in field conditions
Summary
Modern agriculture systems are being intensified through the use of various technologies to achieve maximum efficiency and high qualify products to meet the growing global demand for food supply [1]. PGPR have been used as biofertilizers and/or bioenhancers, as an alternative source of chemical fertilizers to improve soil quality and sustainability and to increase crop production [6,7,8]. More than 95% of the global sweet potato crop is produced in developing countries, and it has vast economic and social importance [9,10] It is well-known for its ability to grow well even in infertile and nitrogen-limited fields [11,12], and nitrogen fixation by endophytic bacteria has been proposed to contribute to this attribute [13]. We treated sweet potato with a commercial biofertilizer, OYK, consisting of a Bacillus strain, which was reported to induce plant tolerance to abiotic and/or biotic stresses and to have antimicrobial activities against pathogens [32]. We examined culturable endophytic communities at harvest in order to obtain further information on the effects of PGPR inoculation on indigenous endophytic bacterial communities in field conditions
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