Propagation of Virus-free Sweet Potatoes through Shoot-tip Culture

Abstract

甘藷感染病毒之病株，以38-42℃熱處理4週以上切取0.3-0.6mm大小之莖頂，培養於含MS基本無機鹽類，每公升添加0.4mg thiamine-HCI、100mg myoinositol，4mg BAP，1mg IAA及30g sucrose之改良式固體MS培養基上，4週後移植於不含生長素之相同培養基，再經1撾，可得完整的培養苗。以指示植物Ipomoea setosa嫁接檢定，剔除病毒殘存株。其餘健康苗，以單莖節培養於改良式MS培養基，每3-4週可繼代培養一次，每次增殖5-6倍，每一莖頂一年約可繁殖40萬苗，對加速健康種苗繁殖，極具功效。 比較健株與罹病株結果發現；具黃斑型及紫斑型病徵之病株，其塊根減產約10%，具捲葉型病徵之病株，嚴重減產30％以上，健株初期生長快，收穫時塊根表皮光滑細緻，肉色亮麗，質量俱佳。 The procedure for producing virus-free sweet potato seedlings by the in vitro .in shoot-tip culture techniques has been established. Shoot tips about 0.3-0.6 mm in length, are excised from the plants previously exposed to high temperature (38~42℃) environment for 28 days. They are cultured for 4 weeks on the medium containing inorganic salts of Murashige and Skoog (MS) formulation supplemened with 0.4mg/l thiamine-HC1, 4 mg/l 6-benzylaminopurine (BAP), 1 mg/l indole -3-acetic acid (IAA), 100 mg/l myo-inositol, 30 g/1 sucrose, and 8 g/l Difco Bactoagar. The cultures are then transferred to medium containing no plant growth regulator, and intact plantlets could be produced within 10 weeks. More than 60% of the produced plantlets are free of virus contamination as proved by mechanical transmission and/or grafting with indicator plants Ipozaoea setosa or I. nil Single-node cuttings of these virus-free plantlets cultured in vitro could develop into intact plants within 20 to 30 days. A 5-time multiplication rate can be achieved after each subculture. A comparison between virus-free and virus-infected plants indicated that the fresh tuber yield was decreased by 30% if the plants were infected with leaf curl virus (SPV-B) and by 10% if infected with yellow spot symptom virus (SPV-A) and/or mild mottle symptom virus (SPV-N). The virus-free plants were also characterized by higher growth rate at early growth phase and better tuber quality