Production of SPFMV-free and SPCSV-free Sweet Potato Using Tissue Culture Techniques

Abstract

Two varieties of sweet potato cultivars SP02 (purple flesh) and SP08 (yellow flesh) were collected from Royal Agricultural Station Inthanon, Chiang Mai province, and planted under greenhouse condition. The plant samples showed viral leaf symptoms, chlorosis and purpling were clearly observed after planting for 90 days. Infections were proved by PCR for both Sweet potato chlorotic stunt virus (SPCSV) and Sweet potato feathery mottle virus (SPFMV). Five criteria severity levels 0-4 (healthy normal-severest) were used to evaluate the diseases in 100 leaf-samples of each variety, results showed no healthy normal detection, severity at level 2 was the major percentage found at 48 and 45% for SP02 and SP08, respectively. Accordingly, the tissue culture plantlets were produced (culturing on MS medium) and used for virus-free production trials using meristem tip cultures with and without thermotherapy (kept under 37±1 °C for 30 days). Excision of the meristem tip from the plantlets at the sizes of 0.3, 0.5 and 1 mm then cultured on the same medium for 90 days after that PCR were used for virus-free evaluation. The trials with thermotherapy of both varieties at the size 0.5 and 1 mm were succeeded to produce high rate of virus-free at 90.9-100%. However, excising of 0.3 mm meristem with thermotherapy trials affected survival rate of plant decreasing to 37.5%. Mass-production of virus-free plantlets testing for various concentrations of plant growth regulators supplemented in MS medium, after culturing for 30 days, the greatest number of node per plantlet of SP02 and SP08 were 11.1 and 13.8 respectively, on the medium supplemented with indole-3-acetic acid (IAA) at the concentration of 0.5 ppm and gibberellin (GA₃) at the concentration of 1 ppm.