- B Tesfagiorgis Demoz and L Korsten
- Department of Microbiology and Plant Pathology, University of Pretoria, Pretoria 0002, South Africa
- 2006
Microbial communities of the phyllosphere are diverse and include bacterial, fungal and yeast genera, which are pathogenic or non-pathogenic to the host plants. Investigating the dynamics between these communities is crucial in understanding the relationship between epiphytic micro-organisms and plant diseases. In view of this, the microbial dynamics of the litchi fruit were studied from flowering till harvest. The study was carried out on cultivar Mauritius in Malelane (2004 and 2005 seasons) and cultivar McLean’s Red in Tzaneen (2005 season). Samples were collected from flowering till harvest from three or four orchards respectively every second week. Total fungal, yeast and bacterial counts were taken of all samples. Results indicate the population density gradually increased from flower bud stage to full bloom and to the senescence stage. A population density decrease afterwards was shown for both cultivars during both seasons. Although the total Penicillium counts fluctuated between samplings, a relatively higher number was observed between flowering and fruit set and at maturity. This could possibly be attributed to the amount of nutrients released from the flowers and the developing fruit and the change in weather conditions during the seasons.
Summary:
The study investigates the microbial community dynamics on litchi fruit surfaces from flowering to harvest, focusing on cultivars Mauritius and McLeans Red in South Africa over 2004-2005 seasons. It aims to understand the relationship between epiphytic microbes and plant diseases, especially Penicillium spp. infection windows.
Samples were collected biweekly from floral bud stage through various fruit development stages in orchards at Malelane and Tzaneen. Microbial populations measured included total fungi, yeasts, and bacteria, enumerated by plating on selective media.
Results showed fungal and yeast populations increased significantly from flower bud to full bloom and senescence stages, with a population decline after fruit set.
Bacterial populations generally decreased from bud to harvest, with some variation by cultivar and season.
Fungal counts, especially Penicillium species, fluctuated but peaked between flowering and fruit set and again near maturity.
However, pathogenic Penicillium species were seldom isolated, indicating minimal pre-harvest infection risk.
Differences were observed between cultivars and locations: cultivar Mauritius had higher microbial loads than McLeans Red; Malelane generally exhibited higher populations than Tzaneen, linked to microclimate and cultivar traits.
The study confirms epiphytic microbial communities on litchi fruit vary dynamically with developmental stage, season, environment, and cultivar, highlighting the importance of nutrient availability and microclimate in shaping microbial succession.
Cladosporium was the most common fungal genus isolated throughout, suggesting it is a widespread pre-harvest fruit surface colonizer.
Understanding this microbial ecology assists in identifying critical periods for pathogen establishment and can inform management practices to reduce postharvest diseases in litchi.
Methodologically, samples were processed with rinsing, ultrasonic treatment, and culture plating; data were statistically analyzed using ANOVA to detect differences across stages, locations, and seasons.
The research contributes crucial baseline knowledge of litchi fruit surface microbiology, previously understudied compared to leaves and other phyllosphere components.