A Study Of The Technology Of The One-year Virus-free Original Potato-Seed Supply In Enshi Prefecture

Potato is the fourth grain crops in the world, which rank only second to corn,rice and wheat. China has the biggest potato-producing area, but the absence of special breeds and low production limit the whole potato development. The high production of potatoes in develped countries derives from culturing the seed potatos with no virus infection and high quality.Enshi Autonomous prefecture in Wuling mountain shares mixed regions for single/double seasonal plantation in southwesten hills, which has the altitude of1000m on average (3005m at the maximum;66.8m at the minimum).The thick and loose soil is yellow brown with an average yearly temperature of13～16℃and the relative humidity of80%～85%. The yearly rainfall is1400mm on average, which makes the climate cool and more rainy. The whole ecological system is suitbale for potato growth and the natural isolation from aphids for the high altitude promotes large propagation of seed potatoes. The usual plantation area of seed potatoes in Enshi every year is approximately120thousand with the production of1000kg/667m2, which are far from the international standard. Besides limited plantation area of high-qualified, pathogen-resistant seed potatoes and the limited introduction of new breeds and new techniques, the low production of seed potatoes can be mainly attributed to the serious degeneration of seed potatoes and the absence of de-poisoning seed potatoes. Therefore, how to propagate the virus-free seed potatoes fast will be a key to all those problems mentioned above.Based on the main potato variety of E-malingshu5, its virus-free tube seedlings are tissue-cultured by different nutrient solutions and later the water culture seedlings are transplanted to the field to produce the virus-free original seeds, which is finished in one year. The paper analyzes the influence of different nutrient solutions on the virus-free water culture seedlings and the influence of density of cultivation screening test on the seed production in order to choose the suitable nutrient solution formula and planting density. The conclusions are as follows:(1) Different nutrient solution formulas should be chosen in different periods including the formative period of roots primitive body, the root period and the growth period.①In the formative period of roots primitive body, all the nutrient solution formulas can increase the number of roots primitive body, among which the induction of No.5formula has the best effect for2379.4strains. The difference is significant contrasted with CK.②In the root period, all the nutrient solution formulas can increase the number of rooting, among which the induction of No.2formula has the best effect for2395.0strains. The difference is significant contrasted with other treatment. The longest root is4.8cm.③In the growth period, the seedling growth traits are excellent contrasted with CK by using different nutrient solution formulas. No.3formula has the best effect. In the12-day growth period, the seedlings grow very well with the average height6.1cm, root number6.5, root length7.2cm, stem diameter0.13cm, internodes number7.2.(2)The most suitable field planting density of potato virus-free seedling is32000plants/667m2, under which the total number of potato chips is the greatest; the proportion of effective potato seeds is largest; economic benefit in unit area is the highest.①In the field planting of the virus-free potato seedling, there exists a negative correlation (r2=0.9816) between the average number of chips of individual and the potato planting density. With the increase of planting density, the average number of chips of individual reduces gradually. The higher the density is, the lower the average number of chips of individual is. Potato chips present a trend of decline after the first increases with the gradual increase of the density. When the field planting density is32000plants/667m2, the number of chips is the highest, for152200grain/667m2.②The number of the less than5g chips becomes greater and greater’with the increase of planting density. The number of5～14.99g chips presents the trend of first increase, then decline and reaches the highest in planting density of32000plants/667m2. There exists a negative correlation between the proportion of more than15g chips and planting density. The higher density is, the less the proportion is.③The number of the effective kind of potato in unit area presents the trend of decline after the first increase with the increase of planting density. When the planting density is32000plants/667m2, the effective kinds of potato are the most for136700grain/667m2.④Based on the economic efficiency evaluation, the production trend of seed potatoes went up and down as the plantation density increased.When the plantation density increased by4000, the comprehensive costs added up to370yuan. Therefore, the maximum net profit per area could be achived when the plantation density was320thousand individuals for667m2.