Dr Shyi-Dong Yeh employs a cross protection-based approach to control crop diseases caused by Papaya ringspot virus (PRSV), East Asian Passiflora virus (EAPV) and Zucchini yellow mosaic virus (ZYMV). One of the main research lines of the Plant Pathology Department at the National Chung Hsing University deals with the control of viral diseases affecting crop plants. To tackle plant viral diseases through cross protection Chair Professor of the Department Dr Shyi-Dong Yeh is collaborating closely with a number of other academics. These include Professor Tsung-Chi Chen (Department of Biotechnology, the Asia University) for the control of thrips-borne and whitefly-borne viruses and Dr Li-Hsin Huang (Toxicology Lab, Taiwan Agricultural Chemicals and Toxic Substances Research Institute) for the possible application and commercialisation of the findings. Papaya and passion fruit are two important cash fruit crops in tropical and subtropical areas. Unfortunately, their large-scale plantation is seriously threatened by the Papaya ringspot virus and the East Asian Passiflora virus, respectively. 'Infection of papaya plantations by PRSV, which is naturally transmitted by aphids, can completely wipe out orchards in a very short time. Similarly, infection by the aphid-borne potyvirus EAPV seriously limits the commercial plantation of passion fruit,' explains Yeh. Alternatively, more widespread, vegetative crops like tomatoes and cucurbits are affected by several viruses in nature and single-valence protective measures are thus insufficient to secure their growth. 'To solve this problem, we are currently engineering multivalent protective mild strains, which can generate protection against several viruses at the same time,' he adds. Cross protection is the process by which plants acquire immunity against a pathogenic virus after infection with a mild, related strain. Although mild strains have been traditionally obtained with chemical mutagens (such as nitrous acid) or physical treatments (such as UV radiation or temperature), Dr Yeh's group employs genetic manipulation of viruses. 'This approach has been used for Zucchini yellow mosaic virus (ZYMV), Turnip mosaic virus (TuMV), East Asian Passiflora virus (EAPV) and Papaya ringspot virus (PRSV),' lists Yeh. Yeh firmly believes in supporting young and early-stage researchers, and several MSc students, PhD students and young post-doctorates participate in all his current projects on passion fruit, papaya and cucurbits. 'They will thus have a chance to learn the cutting-edge developments on cross protection and will become real experts in this area.' In addition, he expects to apply his group's findings to the large-scale immunisation of crops in countries such as Vietnam, Thailand and Mainland China, with which they already collaborate. 'Either through governmental agents or private sectors, we are confident that our cross-protection approach will change the production of passion fruit, papaya and other vegetable crops in these countries', Yeh explains.