Growth and development of sweet potato

Sweet potato belongs to convolvulaceae, sweet potato, perennial or annual creeping herb. Native to tropical and subtropical regions, native to South America, Africa and South Asia.

Temperature: Sweet potatoes like temperature and are afraid of cold. Low temperature is harmful to sweet potato growth. When the temperature drops to 15℃, the growth will stop. When the temperature is lower than 9℃, potato chips will gradually suffer from cold damage and rot. The stems and leaves above the ground quickly lost their vitality and died after being frosted. In the range of 18~32℃, the higher the temperature, the faster the growth rate of sweet potato, and more than 35℃ is not good for growth. The suitable temperature for root tuber formation and swelling is 20~30℃, and the optimum temperature is 22~24℃.

Moisture: Sweet potato has high aboveground and underground yield, lush stems and leaves, developed roots, rapid growth and strong transpiration, so sweet potato needs a lot of water in its life. According to the measurement, sweet potato needs 400~600 cubic meters of water per mu during the whole growth period. Rooting seedling stage and branching tuber stage account for 10~ 15% of the total water consumption, stem and leaf peak period accounts for about 40% of the total water consumption, and tuber rapid expansion period accounts for 35%. The relative water content of soil should be kept at 60-70% in the early and late growth stages, and it is best to keep it at 70-80% in the middle growth stage. Too much soil moisture makes it difficult to supply oxygen, which affects the swelling of root tuber and reduces the dry matter content.

Illumination: Sweet potato likes light and temperature, and it is a crop that is not tolerant to shade. The nutrients it accumulates and stores basically come from photosynthesis. The more sunshine, the more favorable it is to increase production. The photosynthetic intensity of light-receiving leaves is more than 6 times higher than that of shading leaves. The leaves turn yellow and fall off seriously due to insufficient light. Generally, the yield of people with poor light will be reduced by 20~30%, so it is not suitable to interplant tall stalk crops in sweet potato fields. Sweet potato is a short-day crop, and the daily sunshine hours are 8 ~ 10 hours, which can induce sweet potato to blossom and bear fruit. However, long sunshine hours are beneficial to nutrient growth and increase production, and it is better to have about 13 hours per day.

Soil: sweet potato has strong adaptability to soil, good acid and alkali resistance and can adapt to the range of soil pH4.2~8.3. The most suitable soil condition for high yield and high quality sweet potato is pH5~7. Advocating paddy-upland rotation, paddy fields can minimize diseases, weeds and pests in upland fields and redistribute soil nutrients at the same time. It is best to use sandy loam or loam with deep and loose soil layer and good ventilation, which can produce more potatoes with high yield, high yield, good quality, smooth potato skin and good commodity rate. Deep and loose soil layer is beneficial to root growth and root weight gain. If the permeability is good and the oxygen supply is sufficient, it can promote root respiration, root cambium activity, root tuber hypertrophy, microbial activity in soil and accelerate nutrient decomposition for root absorption.

Ventilation: Open ventilation site should be selected. In the middle and late stage of sweet potato growth, vines are dense, and the air between vines contains high levels of harmful gases such as water vapor, which is not conducive to plant respiration and affects photosynthesis. When there are good air circulation conditions in the field, excessive vapour band can be eliminated, and the temperature and humidity between potatoes and vines can be adjusted, so that vines can grow healthily and not grow in vain, and nutrients can be transferred to the ground.

Formation of tuberous roots: Sweet potatoes generally reproduce asexually with stems and vines or tuberous roots. Roots that first occur on the vine nodes of sweet potatoes are called adventitious roots. During the growth of sweet potato, adventitious roots are divided into fiber roots, firewood roots and tuberous roots. See figure 1.

Fiber roots, also known as fine roots or fibrous roots, are long and thin, with many branches and root hairs on them, and have the function of absorbing water and nutrients. Fiber roots grow rapidly and are distributed shallowly in the initial stage of growth; Later, it grows slowly and develops in depth. Fiber roots are mainly distributed in 30 cm deep soil layer.

Chaigen is also called burdock root. When adventitious roots are affected by bad climatic conditions such as low temperature and rainy weather, poor soil conditions or too much nitrogen fertilizer and too little phosphorus and potassium fertilizer, the internal tissues of roots change, and the roots stop thickening halfway to form firewood roots. Chaigen consumes nutrition and has no use value.

Tuberous root, also called storage root, is a kind of potato which can be eaten and processed by people. Sweet potato tuber is not only an organ for storing nutrients, but also an important reproductive organ. Tuberous roots are relatively stout adventitious roots on vines, which grow in soil under suitable conditions of light, temperature, moisture and fertilizer. Sweet potato tuberous roots mostly grow in the soil layer 5~25 cm deep, and rarely appear in the soil layer below 30 cm. Tuberous roots are usually spindle-shaped and round. The basic color of potato skin is white, yellow, red and purple, and the basic color of potato meat is white, yellow, red or purple halo. The content of carotene in potato meat affects the color of meat. According to the research, the growth period of sweet potato is generally divided into four periods, but due to the differences in variety characteristics, cultivation conditions and growth performance, the specific time period of each growth period is also different.

Delayed rooting seedling stage: refers to the survival of each node after potato seedlings are planted. At the stage when the seedlings on the ground begin to grow new leaves, the seedlings can grow independently, and most seedlings grow axillary buds from leaf axils.

Branching and potato-bearing stage: the root system of sweet potato continued to develop, axillary buds and main branches spread out long, the number of leaves increased obviously, the main vines grew fastest, and the stems and leaves began to cover the soil and seal the ridges. At this time, the adventitious roots in the underground part differentiated into small potato pieces, and the number of mature potato pieces in the later stage was basically stable and no longer increased. Varieties with early tubers began to form tubers about 10 day after rooting, and a small number of slightly undeveloped tubers could be seen from 20 to 30 days.

Potato vine synchronization: sweet potato stems and leaves cover the ground until the bee with the highest leaf area growth. Stem and leaf grow rapidly, accounting for about 60~70% of the whole growth period. With the growth of stems and leaves, the photosynthetic products of potato underground tubers are continuously transported to the root tuber and obviously expanded and gained weight, which forms 30~50% of the total weight of the root tuber at this stage.

Potato peak period: refers to the growth of stems and leaves from prosperity to decline until the harvest period, centered on potato expansion. The stems and leaves began to stop growing, the color of leaves changed from thick to light, and the lower leaves withered and fell off. The assimilates of the above-ground parts are quickly transported to the potato pieces, which accelerates the expansion and weight gain of the potato pieces, and the weight gain is equivalent to 40-50% of the total weight of the potato pieces, and the height can reach 70%. The accumulation of dry matter in potato blocks increased obviously, and the quality improved obviously. The main goal of breeding is to increase the yield and the content of starch, protein and carotene. At the same time, it has good characteristics of germination, tuber formation and storage, and can resist drought, waterlogging, barren and pests, and can adapt to cultivation in different seasons. Breeding methods, such as clonal selection, make it easier to select mutant strains that meet the breeding objectives. Introduction and identification is a quick and effective method. Cross breeding is a breeding method combining gene recombination and clonal selection. Sweet potato is a short-day crop, which can blossom, pollinate and bear fruit naturally in Taiwan Province, Guangdong, Guangxi and southern Fujian. In other areas, artificial induction should be used to promote flowering, pollination and hybridization, and seedlings should be cultivated after seeds are obtained; Then asexual propagation is applied, and a variety is bred through multiple identification and comparison.

Grafting combined with short-day treatment is widely used to induce flowering, with sweet potato varieties as scions and related plants as rootstocks; After grafting, the vines are hung, and the short sunshine is treated for 8 ~ 1 1 hour every day, and the temperature is controlled between 25 ~ 30℃ when budding. Avoid insect pollination when flowering. Cross between varieties as planned. Generally, the capsules and seeds will mature after 1 ~ 2 months. In addition, there are inbred line breeding, interspecific hybridization breeding and random group hybridization breeding. There are many breeding methods of sweet potato varieties: ① Multi-stage seedling raising method. Using seedbed to accelerate germination, covering various nurseries with plastic film, planting and transplanting in stages, and propagating seedlings with seedlings. ② Single leaf node planting method. When pruning vines, one seedling per leaf node can improve the utilization rate of potato seedlings. ③ overwintering seedling raising method. Seedlings can safely overwinter in the seedbed, which can save seed potatoes, continuously cut seed potatoes and improve the propagation coefficient. (4) High-quality and high-density seed propagation methods. By selecting excellent varieties of potato pieces, cultivating large plants, cultivating a large number of branches and cutting single-node or double-node seedlings, the propagation coefficient is also very high.

New sweet potato varieties and practical new techniques for high-yield cultivation

Sweet potato is a root crop, which is widely used. It can be used as food, feed and industrial raw material crops, and is planted in more than 0/00 countries in the world. The total output of sweet potato ranks seventh in the world. According to the statistics of FAO, in 2002, the total planting area of sweet potato in the world was 9.765 million hectares, the total output was 65.438 0.36 billion tons, and the average output of fresh potato was 654.38 0.3.9 tons/hectare. The total planting area and total output of sweet potato in China account for 62% and 84% of the world respectively, and the average output of fresh potato is 19.0 tons/hectare.

With the increasing population in China, the demand for agricultural products is increasing, the cultivated land area is decreasing, the water resources are in short supply, and the ecological environment is deteriorating. China's grain demand is under great pressure, and grain supply and demand are in a tight balance for a long time. Sweet potato has less input and more output, and the edible dry matter per unit area ranks first among all kinds of crops. Sweet potato has strong disaster resistance, drought tolerance and barren tolerance, and can also be planted in hilly and mountainous areas. In places where crops are difficult to grow, sweet potatoes can also get better yield.

With the sustained growth of China's national economy and the continuous adjustment and optimization of agricultural industrial structure, the role of sweet potato in ensuring national food security and energy security is increasingly prominent. Sweet potato not only has large planting area and great yield potential, but also has good health care function and high conversion and utilization efficiency. Besides being used as feed and health food, it is also an ideal starch resource and energy crop. Many experts believe that sweet potato is one of the most ideal foods in 2 1 century and one of the most important renewable energy raw materials.

Judging from the current situation, the oil supply situation will be increasingly severe in a long historical period at present and in the future, and the development and utilization of biomass energy has been highly valued by all countries in the world. Sweet potato has high biological yield and high starch yield, which is an ideal raw material for producing fuel ethanol. As a new energy plant, it has attracted great attention from many countries. "Creation of New Energy Sweet Potato Materials and Breeding of New Varieties" has been included in the Tenth Five-Year Plan, aiming at cultivating new energy sweet potato varieties with high yield, high starch and high disease resistance. As a new energy plant, sweet potato will play an important role in China's energy security.