Evaluation of alternative growing media for the production of healthy potato mini-tubers

Pre-basic tissue culture (PBTC) mini-tubers are the first tubers in the potato production chain and preservation of their high health status is of paramount importance to the industry. In GB, PBTC mini-tuber production is mainly concentrated in Scotland. At the time the work was commissioned,  mini-tuber production relied mainly on peat-based growing media, which is largely considered to be a low risk substrate for the presence of plant pathogens. However, there is a UK Government policy-led drive to reduce peat use by professional growers by 2030. Growing media producers are reacting to this and introducing peat-free and peat-reduced alternatives for both amateur and commercial uses. This has resulted in a need to find alternative approaches that are suitable for producing disease-free mini-tubers in order to safeguard the future of the seed potato industry.

This project investigated the use of peat-free and peat-reduced growing media to produce disease-free potato mini-tubers and also considered the in vitro activity of a number of biological control agents to limit growth of important potato diseases.

Results

Disease-free potato mini-tubers can be produced in peat-free growing media. However, tuber yield and individual tuber dimensions tend to be more variable in peat-free growing media with coir, pine bark and wood fibre typically yielding fewer tubers than peat. Wool compost has the most potential for producing mini-tubers in a peat-free system. However, as indicated by variation in tuber yield and quality parameters between glasshouse and the different commercial site trials, optimising this growing medium for use in commercial PBTC mini-tuber production is required, particularly with respect to watering regimes. Using peat-reduced growing media blends also showed promise to help limit the volume of peat used in PBTC minituber production.

None of the peat-free growing media alternatives appear to pose any additional risk to the plant health of PBTC mini-tubers compared to peat.

In terms of biocontrol studies, Bacillus subtilis showed stronger antifungal activity than the Aneurinibacilus migulanus isolates in the in vitro dual culture plate assays.