Detection of NEO in muskmelon fruits inoculated with Fusarium sulphureum and its control by postharvest ozone treatment.

Fusarium rot of muskmelon, caused by Fusarium spp., is one of the most important postharvest decays, that not only causes economic losses but leads to trichothecenes contamination. A rapid and sensitive method was developed for neosolaniol (NEO) analysis in muskmelon inoculated with F. sulphureum, utilizing acetonitrile/water (84:16, v/v) extraction and PriboFast M270 columns purification and UPLC-MS/MS detection. Method validation was evaluated by linearity (R ≥ 0.9990), recovery (88.1-136.9%), precision (RSD ≤ 3.97%) and sensitivity (LOD, 0.5 µg/kg; LOQ, 1.5 µg/kg). The effect of ozone treatment on Fusarium rot development and NEO accumulation in inoculated muskmelon was also evaluated. The results showed that UPLC-MS/MS method was suitable for analyzing NEO in inoculated muskmelon, and 1.10 mg/l ozone treatment for 120 min significantly controlled Fusarium rot development and NEO accumulation in fruits after 5, 8 and 11 days. In vivo tests showed that ozone at 1.10 mg/l effectively degraded NEO in acetonitrile.

The life history of the plant pathogen Pseudomonas syringae is linked to the water cycle.

Pseudomonas syringae is a plant pathogen well known for its capacity to grow epiphytically on diverse plants and for its ice-nucleation activity. The ensemble of its known biology and ecology led us to postulate that this bacterium is also present in non-agricultural habitats, particularly those associated with water. Here, we report the abundance of P. syringae in rain, snow, alpine streams and lakes and in wild plants, in addition to the previously reported abundance in epilithic biofilms. Each of these substrates harbored strains that corresponded to P. syringae in terms of biochemical traits, pathogenicity and pathogenicity-related factors and that were ice-nucleation active. Phylogenetic comparisons of sequences of four housekeeping genes of the non-agricultural strains with strains of P. syringae from disease epidemics confirmed their identity as P. syringae. Moreover, strains belonging to the same clonal lineage were isolated from snow, irrigation water and a diseased crop plant. Our data suggest that the different substrates harboring P. syringae modify the structure of the associated populations. Here, we propose a comprehensive life cycle for P. syringae--in agricultural and non-agricultural habitats--driven by the environmental cycle of water. This cycle opens the opportunity to evaluate the importance of non-agricultural habitats in the evolution of a plant pathogen and the emergence of virulence. The ice-nucleation activity of all strains from snow, unlike from other substrates, strongly suggests that P. syringae plays an active role in the water cycle as an ice nucleus in clouds.

Influence of storage on chemical, microbial and consumer acceptability of a milk-like product made from melon seeds.

The storage stability of melon milk at room (30 +/- 2 degrees C) and refrigeration (10 +/- 2 degrees C) temperatures was determined by analyzing changes in the chemical, microbial and sensory properties of the milk stored for 7 days. The results showed that at both storage temperatures, soluble solids and pH of the milk decreased while titratable acidity increased with storage. The standard plate counts increased appreciably while coliforms were absent in the milk with storage at both storage temperatures. The overall acceptability score of the melon milk dropped during storage, the drop being faster at 30 +/- 2 degrees C than at 10 +/- 2 degrees C. The milk samples stored at 30 +/- 2 degrees C and 10 +/- 2 degrees C were acceptable only within one and three days, respectively; thereafter, they were unacceptable.

Isolation and identification of a phosphate deficiency-induced C-glycosylflavonoid that stimulates arbuscular mycorrhiza formation in melon roots.

Melon (Cucumis melo) roots were inoculated with or without the arbuscular mycorrhizal (AM) fungus Glomus caledonium under low phosphate conditions. High-performance liquid chromatography analysis of the secondary metabolites in butanol extracts from roots revealed that the level of one compound in noninoculated roots showed a significant increase from 30 days postinoculation. No accumulation was observed in mycorrhizal roots and high-phosphate-supplemented roots, indicating that the accumulation of the compound was caused by a phosphate deficiency. The compound was isolated by column chromatography and identified by spectroscopic methods to be a C-glycosylflavone, isovitexin 2''-O-beta-glucoside. The effect of the compound on mycorrhizal colonization in melon roots was examined under low (0.05 mM) and high (2 mM) phosphate conditions. The degree of mycorrhizal colonization in control roots grown under high phosphate conditions (8.8%) was much lower than when grown under low phosphate conditions (22%). The treatment of roots with the compound at concentrations of 20 and 50 microM increased root colonization under both low and high phosphate conditions. In particular, the degrees of mycorrhizal colonization in treated roots grown under high phosphate conditions (25 and 22% at 20 and 50 microM, respectively) were comparable to that in untreated control roots grown under low phosphate conditions (22%). These findings suggest that the phosphate deficiency-induced C-glycosylflavonoid is involved in the regulation of AM fungal colonization in melon roots.