Brown rot update April 2016

The BIOCOMES research team is developing two biological control agents (BCAs) against brown rot (Monilinia spp.) in stone fruit crops. The second year of the BIOCOMES project has been fruitful for the brown rot research team and both BCAs are now in an advanced stage of development and resulted in two good formulations for field trials with promising results that need to be validated next season.

The characterization of both biocontrol agents Penicillium frequentans 909 (National Institute for Agricultural and Food Research and Technology, INIA) and Bacillus amyloliquefaciens CPA-8 (Institute for Food and Agricultural Research and Technology, IRTA) has been practically completed.

Actual situation

• Both BCAs have been characterized under the main environmental conditions (temperature, water activity, pH, photoperiod, and light). The results confirmed that both BCAs have a very wide tolerance as regards pH, temperature and water activity, and can survive under different light exposure conditions. This should enable the BCAs to establish themselves and survive actively under a wide range of environmental conditions.
• Molecular markers have been developed for both BCAs.
• The potential low risk of Pf 909 and CPA-8 has also been demonstrated: a study of the phylogenetic tree of Penicillium showed Pf 909 is further away from mycotoxin producer species. These results confirm the absence of ochratoxin, citrinin, patulin, and penicillic acid recorded from samples with Pf 909 analyzed by Graz University of Technology (TUG). On the other hand, IRTA demonstrated the absence of genes linked to enterotoxin production in the CPA-8 strain.
• The results indicate that the main mode of action of Pf 909 against pathogens is a competition for space and nutrients during the germination process on the fruit surface (INIA). Meanwhile, CPA-8 produces fengicines, iturines and surfactines, which are the main lipopeptide compounds associated with the main mode of action in subtilis and B. amyloliquefaciens BCAs (TUG and IRTA).

Production of the BCAs

Pf 909 is a high spore producer in solid state processing; conidia yields are economical and different fermentation trials show stable results. The establishment of the production process under pilot plant conditions for Pf 909 was completed and production has been scaled up successfully. Bayer CropScience Biologics (BCSB)

CPA-8 production (media and conditions) has been optimized and scaled up to a 90-L bioreactor obtaining an economically viable medium with a high production yield, a stable, repeatable and easily scalable process (IRTA).

Optimization of the BCA formulation process

BCSB optimized the liquid formulation of Pf 909 in order to improve persistence on the fruit surface and the two best formulations were prepared for the season field trials in 2015.

The tested liquid formulations appeared to be unsuitable for CPA-8. A fluid bed spray-drying system seems to be the best method to formulate CPA-8 although reasonable results have also been obtained with freeze-drying. Carriers, protectants, binders and process conditions of fluid bed spray-drying system have been optimized for CPA-8 and the best two formulations have been prepared for the field trials (IRTA).

Field trial results in 2015

The formulated BCAs were tested in field trials by OPENNATUR and IRTA, alone or in combination, and were applied by calendar (four applications) or following a prediction model advice developed by IRTA and INIA.

Both BCAs, by calendar or prediction model, showed a good efficacy, comparable to chemicals under a standard level of Monilinia spp. However, high disease pressure reduced the efficacy of biocontrol strategies. It was also concluded that the combination of BCAs did not improve the efficacy in comparison with separate application.

Next season, all these results will be validated under commercial conditions in Italy by BIOGARD, in Belgium by PCFruit, and in France and Spain by OPENNATUR.

See our earlier update on brown rot:

• March 2015

Read more about our activities on brown rot.

Field treatments against brown rot with BCAs Pf 909 and CPA-8. (Picture: IRTA, Catalonia, Spain).