Efficacy of a Nonpathogenic Acidovorax citrulli Strain as a Biocontrol Seed Treatment for Bacterial Fruit Blotch of Cucurbits

Abstract

Johnson, K. L., Minsavage, G. V., Le, T., Jones, J. B., and Walcott. R. R. 2011. Efficacy of a nonpathogenic Acidovorax citruiii strain as a biocontrol seed treatment for bacterial fruit blotch of cucurbits. Plant Dis. 95;697-704.Bacterial fruit blotch (BFB), cau.sed by the seedbome, gram-negative bacterium Acidovorax citruiii, is a serious threat to cucurbit seed and fruit production worldwide. Because of the lack of effective management strategies, we investigated the efficacy of a nonpathogenic A. citrutli strain as a biological control seed treatment for BFB. For this study, we generated a type III secretion system mutant of A. citruiii, AACOO-lA/ircC, that was nonpathogenic on watermelon but retained its ability to colonize germinating watermelon seed. With watermelon seed naturally infested with A. citruUi, AACOO-lA/ircC reduced BFB seedling transmission by 81.8% relative to control seed. In comparison.another A. citruiii antagonist, ,4. avenae strain AAA 99-2, reduced BFB seedling transmission by 74.6% for seed samples from the same lot. Additionally, when female watermelon blossoms were protected with AACOO-lA/iirC and subsequently challenged with AAC()O-1, the resulting seedlots displayed 8% BFB seedling transmission. This was not significantly different than seed from blossoms protected with AAA 99-2 (4%) but significantly less than those from blossoms protected with 0.1 M phosphate-buffered saline (36%). These results .suggest that nonpathogenic A. citruiii has potential as a biological control seed treatment component in a comprehensive BFB management program.

Acidovorax citrulli: generating basic and applied knowledge to tackle a global threat to the cucurbit industry

“…Using a T3S system AAC00‐1 mutant, Johnson et al . () reported that, during the first 6 days of seed germination, A. citrulli grows as a saprophyte, as it does not require effector proteins to colonize watermelon seeds. On the basis of this observation, it was hypothesized that other factors, possibly T2S enzymes, might be involved in watermelon seed colonization by A. citrulli .…”

Quorum Sensing Contributes to Seed‐to‐Seedling Transmission of Acidovorax citrulli on Watermelon

“…In preliminary studies, we observed that a non‐pathogenic A. citrulli type III secretion system mutant (AAC00‐1∆ hrcC ) retained the ability to colonize seed during the first 96 h of germination (Johnson et al. ). However, by 6 days after planting, AAC00‐1∆ hrcC population growth declined significantly relative to the wild‐type strain.…”

New Technique to Create a Suspension Containing Bacteriophages and How It Can Be Used to Control Cabbage Leaf Spot Caused by <i>Xanthomonas campestris</i> PV. <i>campestris</i>

“…By changing the methodology proposed by Romeiro [6], suspensions containing phages showed to be efficient biological controllers by inhibiting in vitro the growth of the pathogen in 48 h. Often, microorganisms containing an enzymatic arsenal (bacteriocins and toxins), such as fungi and bacteria, need to screen hundreds of isolates [21]. The time period is used for screening changes when virions highly specific to their host are used in biological control [22].…”