Study On Cultural Physiology Of High Yield On Virus-free Sweetpotato

Sweet potato is a kind of crop for food, feeds, and industrial materials. It plays animportant role in agriculture production. Sweet potato virus is a serious disease in thewourldwide and is becoming more and more severe. There have been no anti-virus agentiasand anti-virus gene resource yet. An effective way is to extend sweet potato with virus-free.In this paper, we studied on cultural physiology using four generations of sweet potato(cutting) with virus-free from cultivar Xu Shu NO.18 in Luoyang suburb and HenanUniversity of Science and Technology during 2002～2004. The result as follows:1. The stems and leaves of vine-tip cutting, original cutting, stock and improvedvariety cutting from four generations was growing fast in early stage, speeding in mid stage.It helped form the area of photosynthesis. The outcome of photosynthesis moveed downand helped enlarge the storage in later stage. The Leaf Area Index (LAI) was increasingfast in early stage to form a larger area of photosynthesis. During 90～110d aftertransplanting, root tuber expanding speed line reached to the peak. The trend ofphotosynthesis appeared stronger during the whole growth.2. The accumulations of biological and economical yields of the four generations with virus-free were significantly higher than those of the check. The features of distributionwere the outcome of photosynthesis distribution into the upper stem and leaves, thentransmittion to underground parts increasingly.3. Dry matter growth rate (DGR) reached to the maximum in the growing period offour generations with virus-free cutting in 90～110d after transplanting. DGR of fourgenerations reached the peak 0.25t/h m~2.d, 0.238t/h m~2.d, 0.172t/h m~2.d, 0.136t/h m~2.d,respectively. They were higher 97.6%, 87.4%0, 35.4% and 7.1%, respectively, than thoseof the check.4. Relative Growth Rate (RGR) and Net Assimilation Rate (NAR) of dry matter yieldof four generations with virus-free cutting, all appeared advantageous obviously in 70 daysafter transplanting. Their dry matter yields were 76.89g/p, 67.17g/p, 59.99g/p and 53.89g/p,respectively, and increased weight 78.4%, 55.9%, 39.2% and 25.1% comparing with thecheck, respectively. The RGR were 67.16mg/g.d, 63.30mg/g.d, 60.75mg/g.d and58.94mg/g.d, higher 19.6%, 12.8%, 8.2% and 5.0%, resepectively. The NAR were 7.33g/m~2.d, 7.22g/m~2.d, 6.4g/m~2.d and 6.25g/m~2.d, resepectively, which were higher 33.0%, 31.0％, 16.3％and 13.4％than those of the check. The Leaf Area Rate (EAR) of fourgenerations was lower than those of the check. 5. Sweet potato (seedling) with virus-free had an outstanding extension foreground inHenan province. We will popularize its key technique further and establish a perfectcultural and examinational system of Sweet potato (seedling) with virus-free.