Environmental monitoring of the biocontrol agent Pantoea agglomerans CPA-2 applied to citrus fruit at preharvest

Abstract

The aim of this study was to evaluate the environmental fate and behaviour of the biocontrol product based on Pantoea agglomerans CPA-2 cells after its release into the field. Three different methods, dilution plating, quantitative real-time PCR (qPCR) and propidium monoazide combined with qPCR (PMA-qPCR) were used to track the CPA-2 population. Populations quantified by qPCR were statistically different compared with those by the PMA-qPCR and dilution plating methods. In addition, the spray dispersion of the CPA-2 treatment was evaluated using water-sensitive papers. A lack of dispersion of the CPA-2 treatment was observed at distances of 2.5 ± 0.5 m. The presence and persistence of CPA-2 in the environment were monitored in different areas, by dilution plating and confirmed by conventional PCR. The results showed that CPA-2 can survive but not proliferate on weed and leaves. The persistence on inert surfaces, such as motorised backpack sprayer, gloves and working clothes, was less than 7 days. In conclusion, PMA-qPCR was a potential tool for fast and specific monitoring of viable populations of CPA-2 and it gave valuable information on population behaviour. Moreover, the results demonstrate that CPA-2 would not present a risk for the environment because of its low establishment, survival and dispersion.

The authors would like to thank Cristina Solsona and Cèlia Sánchez for their excellent technical assistance in field sampling. The authors are grateful to the Spanish Government for financial support by national projects RTA2009-00053-00-00 (Plan Nacional de I + D + I, Ministerio de Ciencia e Innovación, Spain) and the National Council of Science and Technology of México (CONACYT) for L. Soto Ph.D. grant 198363.