Viruses and their impact on the utilization of plant genetic resources in the Pacific

Banana, breadfruit, edible root and tuber crops, such as taro, yam and sweetpotato are important staple food crops in the Pacific. Cultivation of these crops is almost exclusively by vegetative propagation, which presents challenges in the sharing and exchange of plant material because of the vertical transmission of viruses. The symptomless nature of many viruses means that infected planting material is frequently used, often leading to yield reductions in subsequent planting cycles. Co-infection by different viruses and the presence of multiple strains of a virus (some more virulent) present another dimension for consideration. Viruses can be a significant constraint in the exchange and utilisation of these crops within the region and globally. No country is self-sufficient in plant genetic resources and climate change will reinforce the interdependence of countries, making it increasingly important to share diversity. As biosecurity regulations require plant material to be certified as virus free, the sharing of, for example, breeding lines developed by different countries for traits such as disease resistance and climate resilience is often hindered by the presence of viruses. In the Pacific, Taro bacilliform virus (TaBV) in aroids occurs frequently but is very hard to eliminate. Similarly with yams, badnavirus infection is also preventing the sharing of valuable diversity especially as effective protocols for detection are lacking. This paper discusses these challenges, highlighting the need to address the issue of viruses when establishing plant genetic resource collections. The paper also discusses different approaches to ensure diversity gets to the farmer using formal and informal approaches.