Violeta Rojas, Agricultural Engineer – Head of the Field and Sampling Department, Diagnofruit Laboratories Ltda.
The fruit production chain involves various stages during the season, which, from a phytosanitary point of view, have different management and handling methodologies that allow quality and productivity to be maintained throughout the production process. Within this, the post-harvest phase requires significant control of the pathogen load to prevent the development of fungi during the packing, transportation, storage and marketing of the fruit both in Chile and in the destination markets.
To achieve this purpose, there are, within the industry, many tools to collaborate with the care of the fruit and generate a final product that is harmless from a phytopathological point of view, such as the use of refrigeration, fungicides, additives, etc. However, within all these tools, it is essential to add the monitoring of phytopathogens, in the field and post-harvest, today a critical analysis, which must necessarily provide accurate data and a response in a limited time.
Specifically, quantification of phytopathogens in post-harvest is characterized by sampling of inert surfaces such as walls, instruments on packaging lines, taking water samples and analyzing fruits as a finished product, with the intention of detecting and quantifying the presence of microbial load to generate control, knowledge and projection of the health status of the processed fruit during its transportation and marketing.
Sampling sectors within the cherry packing plant
The hydrocooler is the first operation performed in the processing plant, with the purpose of rapidly decreasing the temperature of the fruit, helping, at the same time, to hydrate the pedicels. As it is the first sector where the fruit is processed, the load of organic matter and soil is very high (many times this dirt is stuck in the boxes and bins) these characteristics transform the hydrocooler into the first critical point where we must carry out monitoring. Organic matter decreases the sanitizing action of chlorine, therefore, real-time control of active color is important, but at the same time the quality of this injection must be monitored through a direct biological test, such as the quantification of phytopathogens.
Continuing with the fruit route within the processing plant, the next stage is the water area of the drainer, where a first immersion and second wash are carried out after having been on hold in the maintenance chamber. In this phase, there is still a significant load of leaves and darts, which have inoculum, therefore, we must know if the management of the sanitizer is sufficient to combat the dissolved microorganisms, so we must accompany it with monitoring of phytopathogens to define effective chlorine concentrations, water change frequencies, etc.
Subsequently, the water of the stick cutter, followed by the fungicide pond, are sectors where the phytopathogen load should be close to zero, due to the washing and sanitizing effect of the previous processes, obviously, if everything goes well. With this premise, we must schedule sampling, in at least one of the two pools, to ensure that the water sanitization is working, favoring the sector of the stick cutter.
qPCR-based analysis technique
Five years ago, through CORFO funding, Diagnofruit’s R&D department began exploring the use of the qPCR technique to analyse field and packing samples, with the aim of quantifying phytopathogenic microorganisms. The project was successful and has already been in commercial sales for three seasons, through: “Service for the Detection and Quantification of Phytopathogens in Packaging Lines”. In this way, our laboratory develops monitoring plans for the aforementioned sectors and processes tailored to the client’s needs.
In particular, the service in cherries focuses on the detection and quantification of phytopathogens through qPCR, focused on Botrytis, Alternaria, Geotrichum and Penicillium. In addition, the molecular detection and quantification service will soon begin. CladosporiumDue to the high sensitivity of the technique, the service is highly reliable and at the same time its speed allows results to be delivered between 48 and 72 hours after the sample is taken.
Today, it is essential to keep the inoculum load under control, due to the lengthy marketing and transport processes; therefore, monitoring through qPCR becomes a fundamental critical point control tool that Diagnofruit exclusively makes available to the cherry production and export industry.
