Biosolarization and biofumigation using virus-infected crop debris fail to inactivate tomato brown rugose fruit virus and cucumber green mottle mosaic virus in soil and substrates

Soil biofumigation (SBF) and biosolarisation (SBS) are sustainable practices used for the control of soilborne pathogens, parasitic nematodes and weeds, based in the burial of fresh organic matter in the agricultural soil. The use of in-farm crop debris for SBF and SBS, allows farmers to conform to circular economy and bioeconomy guidelines, together with the management of the mentioned crop health issues. ToBRFV and CGMMV are currently the most alarming tobamoviruses affecting tomato and cucurbitaceous crops worldwide, respectively. In the present paper we used plant debris from tomato and cucumber plants infected with ToBRFV and CGMMV, respectively, to perform SBF and SBS, with the aim of controlling both viruses. SBF and SBS conditions were simulated under controlled experiments using a soil from a Mediterranean greenhouse, as well as three crop substrates: perlite, peat moss and coco peat. Treated soils were analyzed at 15 days intervals until day 60, by means of bioassays for virus detection and symptomatology on tomato/cucumber seedlings cultivated for 3 weeks. Results evidenced that burying plants infected with ToBRFV or CGMMV as biofumigant material in soil and substrates under biosolarization or biofumigation conditions for up to 2 months did not alter the ability to transmit the virus to susceptible seedlings, causing the expression of viral symptoms and accumulating high viral loads. Incorporating plant debris in SBF and SBS treatments benefits Mediterranean greenhouses by reducing waste, enriching soil organic matter, and controlling soil pathogens. However, using tobamovirus-infected debris poses a high risk of virus transmission, leading to soil contamination and limiting the cultivation of susceptible plants.