Biological Control of Grape Crown Gall byRahnella aquatilisHX2

Abstract

Crown gall induced by Agrobacterium vitis is a worldwide plant disease in grape-growing regions. Rahnella aquatilis HX2, a new isolate from vineyard soil in Beijing, showed a significant inhibition effect on the development of crown galls in grapevines. In field trials, immersion of the basal ends of grape cuttings with HX2 cell suspension inhibited or completely prevented crown gall formation caused by A. vitis K308 in the roots of the plants from the cuttings. The 3-year average disease incidence in grape plants treated with HX2 was 30.8% compared to 93.5% in plants without HX2. The culture supernatant of HX2 exhibited a stronger inhibition effect on disease development than did the cell suspension. HX2 could be found in the grape rhizosphere, grown under field conditions, for up to 90 days after inoculation. There was no significant difference in the mean population sizes of root microflora between plants treated and not treated with HX2. The inhibition effect of HX2 on crown gall in sunflower, caused by different agrobacterial strains, varied between 30.7 and 100%, depending on strains. Our results showed that Rahnella aquatilis HX2 may be used as a biological control agent for crown gall disease of grapes.

Mutations That Disrupt Either thepqqor thegdhGene ofRahnella aquatilisAbolish the Production of an Antibacterial Substance and Result in Reduced Biological Control of Grapevine Crown Gall

“…However, K84 could not prevent the infection of grapevines by A. vitis (6). Consequently, several bacterial strains were identified for suppression of grapevine crown gall, including nontumorigenic Agrobacterium strains, such as A. vitis E26 (35), A. vitis F2/5 (8), and A. vitis VAR03-1 (29), and two Pseudomonas strains (3,31), as well as two strains of Rahnella aquatilis (3,12). Although these bacteria have been shown to provide some level of control of grapevine crown gall, effective methods of biological control in fields are not clearly defined.…”

Draft Genome Sequence of Rahnella aquatilis Strain HX2, a Plant Growth-Promoting Rhizobacterium Isolated from Vineyard Soil in Beijing, China

“…Strains belonging to the genus Rahnella have been isolated from several environments, including soil, freshwater, marshes, food, seeds, plant roots, and clinical samples (4,6,10). Plant-microbe interactions have been studied with members of this genus as related to plant growth promotion, nutrient acquisition, and disease control (1,3,4). R. aquatilis strain HX2 was isolated from vineyard soil in Beijing.…”

“…R. aquatilis strain HX2 was isolated from vineyard soil in Beijing. This strain has the ability to solubilize mineral phosphate, fix nitrogen, and produce pyrroloquinoline quinine, indole-3-acetic acid, and antibacterial substances (4,5). It colonizes the root surfaces of maize and grape and has been evaluated as an inoculant for plant growth promotion (4).…”

“…This strain has the ability to solubilize mineral phosphate, fix nitrogen, and produce pyrroloquinoline quinine, indole-3-acetic acid, and antibacterial substances (4,5). It colonizes the root surfaces of maize and grape and has been evaluated as an inoculant for plant growth promotion (4). Draft genome sequencing of this strain was conducted to obtain additional insights into physiological characteristics involved in plant growth promotion and disease control and for future studies examining the molecular basis of these traits.…”

“…The draft genome of R. aquatilis strain HX2 contained three replicons, which comprised a circular chromosome (4,962,173 bp) containing 4,541 ORFs and two circular plasmids, which were named pRA1 (570,951 bp) and pRA2 (123,675 bp), carrying 519 and 120 predicted ORFs, respectively. There still is a gap in plasmid pRA2.…”