Mechanism of Tomato Bacterial Wilt Suppression in Soil Amended with Lysine

Abstract

The effect of four amino acids, unutilizable by Ralstonia solanacearum, on tomato bacterial wilt (TBW) was tested in three Japanese soils. Results confirmed our previous findings that the addition (2.5 mg g −1 soil) of lysine and serine suppressed TBW, but that of tyrosine and valine did not. The number of the pathogen in non-rhizosphere soil, rhizosphere soil and the rhizoplane was markedly lower in the lysine and serine treatments than in the tyrosine and valine treatments, while the opposite result was obtained for the total bacterial population. Substrate-induced respiration analysis revealed that bacteria became more predominant in the amino acid treatments, especially in lysine. There were no apparent correlations between the microbial activities in soil and the disease index. PCR-DGGE targeting the 16S rRNA gene of the rhizoplane samples from lysine-added Nagoya, Fuchu and Iwate soils revealed 10, 1 and 2 unique bands, respectively, indicating shifts in bacterial community. DGGE patterns in the suppressive treatments belonged to the same cluster while the not suppressive treatments clustered differently. The lower disease incidence of TBW following lysine treatment is likely related to a specific bacterial community in the rhizoplane that developed on the addition of lysine.

Bacterial Monitoring with Adhesive Sheet in the International Space Station-“Kibo”, the Japanese Experiment Module

“…The yield of PCR products with a 8f/1492r primer set or an EUB f933-GC-clamp/EUB r1387 primer set was too low to construct 16S rRNA gene clone libraries or perform PCR-DGGE followed by sequencing, respectively; therefore, we used nested PCR-DGGE followed by sequencing to obtain phylogenetic information of bacteria present in Kibo. This approach showed the presence of bacteria, although it did not reflect the dominance of any particular species (15). Fig.…”

Recent Trends in Control Methods for Bacterial Wilt Diseases Caused by <i>Ralstonia solanacearum</i>

“…The application of lysine to a pumice culture medium (0.25 mg g −1 ) and soil (2.5 mg g −1 ) reduced bacterial wilt in the tomato by 85–100% (48, 87) and by 58–100% (97), respectively. The suppression mechanism was not attributed to the induction of systemic resistance, but to shifts in the soil microbial community structure that led to the more rapid death of the pathogen (98). In contrast, riboflavin induced a series of defense responses and secondary metabolism in cell suspensions and, thus, protected tobacco against R. solanacearum (75).…”

A Coevolutionary Framework for Managing Disease-Suppressive Soils

“…In total, there is compelling experimental evidence that nutrient availability is likely to have a significant positive effect on microbial densities, rates of coevolution, and the relative fitness benefits of antagonistic phenotypes, all of which are critical to the development of disease-suppressive microbial communities. Nutrient inputs have long been recognized as useful for enhancing disease suppression in soil, yet there is substantial variability in the effects of different inputs on disease suppression (49,60,93) and on the effects of the same input on disease suppression in different fields or the same field in different growing seasons (83,110). This variability is a constraint to the practical use of organic inputs for disease management.…”