Growth Retardation And Improvement Of Potato Microtubers Plants

Potato microtubers plays an important role in virus-free seed-potato production, with a wide adaptation. Compared with the conventional seed tubers, virus-free microtubers have advantages in minimizing geographical and seasonal restrictions of the production, insuring high purity and quality, as well as in reducing seed tubers size, attaching microtubers a potential to replace the conventional seed.However, potato microtubers exhibit lagged plant development in early growth stage, hence a low tuber yield. It is critical, therefore, to understand the factors that influence the early growth of microtuber plants for a better crop management. In present research, potato variety "Favorite" was used to produce microtubers for monitoring the sprouting rate, nutrient contents (mainly carbohydrates, dry matter, nitrogen, phosphorus, potassium), and endogenous growth substances before and after sprouting, as well as the effects of fertiliz, transplanting on the grow, in comparison to the minitubers with a set of tuber size grades (conventional tubers). The main results are as follows:1. Microtuber dormancy was10days longer than18～22g conventional tuber, while about one week shorter than0.5～1.0g conventional tuber. The shoot was sig-nifycantly lower than18～22g conventional tubers, but comparable to0.5～1.0g conventional tubers.2. Determining by enzymatic method, the content of sugars between potato microtubers and four grades of conventional potato tubers (0.5～1.0g,1.5～2.5g,8.5～12g,18～22g) before and after tuber sprouting showed that the contents of glucose, fructose, sucrose of conventional tubers were higher. In conventional potato tubers, the content of sugars decreased with the increase of tuber weight, and the content of starch just the opposite.3. Comparison between microtubers and18～22g conventional tubers, the content of gibberellin (GA3) in microtubers was lower than that in conventional tubers when sprouting, and as well as the content of indole acetic acid (IAA) when15days after sprouting.4. Comparison between microtubers and18～22g conventional tubers, the content of dry matter in microtubers was lower than that in conventional tubers, and the content of nitrogen, phosphorus, potassium and the rate of water loss were the opposite.5. An optimal formulation of rooting solution for enhancing early root growth of microtubers was selected as200mg/L IBA,100mg/L NAA,175mg/L boric acid,20mL/L Tween-80(pH5.5)(International Potato Center).The results showed that treated with this solution could promote root development in the early growth stage but no significant effects on final tuber yield of the microtuber plants.6. By setting up the experiments to look at the influence of fertiliz addressing, the time of the nursery, the size transplanting plants on the early growth and yield of the microtuber plants, are able to show that increase in amount of nitrogen and potash fertilizers could not promote early growth and development of the plants, neither the yield. However, the plant growth could be improved by culturing earlier the microtubers in nursery-plate and transplanting them in the earliest favorable season. A delayed nursery or transplanting large-sized plants may significantly reduce the growth and development of the plants.