Impact of clean planting material technology (CPM) on the incidence of virus kulot disease in major sweet potato production areas of Tarlac [Philippines]

Sweet potato production in Luzon [Philippines] has been plagued by a virus disease complex locally known as 'camote kulot'. It caused more than 50% reduction in yield, and was also responsible for the loss of an important variety with good and well-accepted agronomic characteristics. Interagency efforts resulted in a technology in the production of clean planting materials through thermotherapy and meristem culture. A sweet potato variety has been cleaned up, reproduced and multiplied for farmers use. CIP-UPWARD supported the use of participatory R and D approaches to adapt CPM in sweet potato-associated livelihood systems in the region. The program implemented livelihood systems analysis, farmer field schools and farmer participatory researches. The results indicated the role of participatory approaches in facilitating project outputs and outcomes. PR and D approaches intensify awareness of research and development institutions about 'kulot' and the potential of CPM in solving it leading to their provision of resources and other support to its solution. CPM were produced and used by 117 farmers in 19 villages of the provinces of Tarlac and Bataan. In 2003, Farmer Participatory Research (FPR) was conducted to compare the yield and level of virus infection of CPM and non-CPM with or without disease management and determine percent decline in yield at each level or stage of multiplication. CPM gave both increased yield and better quality plants because of its greater rooting ability, more rapid growth and earlier tuber formation than non-CPM plants. On farm trials showed higher yield of CPM from TCA (27%) and from FFS nethouses (13%), respectively as compared to cuttings from farmers' fields. Kulot incidence using the same materials is also rated very low and low and observed at later stages of crop growth in fields planted with CPM as compared to moderate at earlier stages observed in farmers' cuttings. The 2004-2005 and 2008-2009 resurveys for viruses, determined the incidence and diversity of viruses present in Tarlac [Philippines]. Symptomatic and asymptomatic sweet potato showed the presence of SPFMV or a combination of SPFMV-SPCSV or triple infection with SPFMV-SPCSV-SPCFV. Virus prevalence varied greatly with SPVMV-SPCSV combined infection occurring in more than 60% infection, followed by the multiple infection with SPFMV-SPCSV-SPCFV. Single infections of either of the viruses occurred with infection ranging from 5-10% only. Higher virus incidence of 55-100% was observed in Paniqui areas where CPM is not used while virus infections was somehow reduced in some towns that used CPM in 2009.