Abstract
Modern molecular ecology techniques were used to demonstrate the effects of plant genotype and environmental conditions prior to harvest on the spinach epiphytic bacterial community. Three cultivars of spinach with different leaf topographies were collected at three different periods during the fall growing season. Leaf surface topography had an effect on diversity and number of culturable bacteria on the phylloepiphtyic community of spinach. Savoy cultivars, which had larger surface area and more stomata and glandular trichomes, where bacterial aggregates were observed, featured more diverse communities with increased richness and larger bacterial populations compared to flat-leaved cultivars. Bacterial community richness was compared using denaturant gradient gel electrophoresis (DGGE), while abundance was quantified using 16s rRNA primers for major phyla. The most diverse communities, both in richness and abundance, were observed during the first sampling period, immediately following a period of rapid spinach growth. Exposure to lower air and soil temperatures and decreased precipitation resulted in significantly reduced bacterial population size and bacterial community richness in November and December. This study describes the effect of the plant characteristics and environmental conditions that affect spinach microbiota population size and diversity, which might have implications in the survival of food and plant bacterial pathogens.
Highlights
Phyllosphere microbial communities are diverse, consisting of bacteria, fungi, algae, protozoa and, infrequently, nematodes
190 growing degree units (GDUs) were accumulated in November and 85 in December so little crop development occurred after first harvest
The phyllopshere bacterial community of spinach is influenced by environmental conditions prior to harvest and the host genotype
Summary
Phyllosphere microbial communities are diverse, consisting of bacteria, fungi, algae, protozoa and, infrequently, nematodes. Phylloepiphytic bacteria that successfully colonize the leaf surface must survive adverse conditions including nutrient limitation, low water availability, and UV irradiation which all affect bacterial fitness and diversity [1,2]. The membership of these phyllosphere communities is dominated by members of a few phylogenetic groups, α-proteobacteria, γ-proteobacteria and Bacteroidetes. Differences in leaf surface topography and nutrients are important factors that affect the microbial community of the phyllosphere [14,15]. Water availability and plant secondary metabolites influence total microbial populations [7,18]. It is possible that changes in leaf blade topography might be related to changes on the leaf surface, influencing the microbial diversity and population size on plants
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