Breeding and Cultivation Points of the High-Starch Potato Variety Qingshu No. 2

The new high-starch potato variety Qingshu No. 2 was bred by the Crop Institute of the Qinghai Academy of Agriculture and Forestry Sciences. This variety is a late-maturing variety with a growth period of about 120 days, good agronomic traits, strong growth vigor, strong disease resistance, and excellent quality; its starch content is 22.86%-25.83%, which is 7-10 percentage points higher than the average value of the 77 nationally approved varieties (15.05%), and its Vc content is 20.92mg/100g; it tastes good and has a high yield level, with an average yield of 3000kg per mu and a maximum yield of 4192kg per mu; it has wide adaptability and is suitable for planting in the single-cropping region of northern China.

1 Variety Origin

The Crop Institute of the Qinghai Academy of Agriculture and Forestry Sciences used the institute-bred Plateau No. 4, which has strong disease resistance, high yield and excellent quality, as the female parent, and carried out sexual hybridization with the introduced foreign variety Magura as the male parent. In 1992, single-plant selection was carried out on seedlings, followed by multi-generation screening of clones, as well as regional trials and production trials, and it was developed through accelerated propagation. The original code number was 92-3-28, called Qingshu 328. In 1999, it passed the approval of the Qinghai Provincial Crop Variety Approval Committee and was named Qingshu No. 2.

2 Characteristics and Traits

2.1 Plant Traits The plant form is upright, the plant cluster is luxuriant, and the growth vigor is strong. The plant height is 88±10.33cm, and the stem diameter is 1.15±0.12cm. The stem is green, and the stem cross-section is triangular. The stem wings are straight. The number of main stems is 2.2±0.42, and the number of branches is 6.1±0.99, with a relatively high attachment position; the leaf color is dark green, the leaves are medium-sized, and the margins are flat. The compound leaves are elliptical, with medium-dense arrangement, alternate or opposite; there are five pairs of lateral leaflets, the terminal leaflet is obtuse, and there are eight pairs of secondary leaflets, alternate or opposite, with the second pair being larger, and the stipules are sickle-shaped.

2.2 Flower and Fruit Traits The inflorescence is a cyme, with 7-10 flowers, relatively loosely arranged. The flower buds are elliptical, green with purple. The total peduncle is 12-18cm long, the pedicel joint is purple, and the sepals are scallion-green and lanceolate. The corolla is light purple, with a diameter of 3.4±0.2cm. The petals are pointed and light red, and the base is light green. The pistil style is relatively long, and the stigma is round, five-cleft, and green; there are 5 stamens, cone-shaped and yellow; the natural small berries are round and green.

2.3 Tuber Shape The tuber shapes include round and elliptical. The skin is smooth, white skin, white flesh, compact in density, and without hollow heart; the eyes are relatively line-like, the number of eyes is 7.82±1.22, the eyebrow is straight, and the navel is shallow; the tubers are concentrated, the dormancy period is long, and it is resistant to storage.

2.4 Economic Traits The yield per plant is 0.88±0.3kg, the number of tubers per plant is 4.8±2.25, and the single tuber weight is 0.18kg. The starch content of the tubers is 25.83%, and the steamed food tastes good; the vitamin C content is 20.9mg/100g, the crude protein content is 1.66%, and the reducing sugar content is 0.6267mg/100g.

2.5 Growth Period It is a late-maturing variety, with a whole growth period of about 160 days, during which the accumulated temperature above 5°C is 2208.4°C. The number of days from sowing to emergence is about 42 days, during which the accumulated temperature above 5°C is 367.10°C. From emergence to budding is about 30 days, during which the accumulated temperature above 5°C is 373°C. From emergence to maturity is about 88 days, during which the accumulated temperature above 5°C is 1467°C. The growth period is about 118 days, during which the accumulated temperature above 5°C is 1841.3°C.

2.6 Variety Resistance The plants are relatively drought-tolerant, cold-tolerant, and salt-alkali tolerant, and the tubers are storage-resistant; resistant to potato mosaic virus and leafroll virus, and resistant to late blight, ring rot, and blackleg.

3 Yield Level

3.1 Variety Comparison Trial In 1992, on the basis of sexual hybridization, the propagation and selection of seedlings was carried out. Seedlings of 4000 plants from 32 combinations were planted in plastic greenhouses. Through observation and selection, 113 excellent single plants were selected from the 32nd combination, accounting for 9.34% of the total selected plants. The selected single plant 92-3-28 showed dark leaf color, strong growth vigor, concentrated tuber formation, 7 tubers, white skin and white flesh, and a yield per plant of 585g, making it one of the higher-yielding selected materials. In 1993, on the basis of the previous year's seedling selection, a first-generation clonal variety comparison was carried out, with a yield of 2858.57kg per mu, an increase of 14.34% over the control variety Qingshu 168; in 1994, in the second-generation clonal variety comparison trial, the yield was 3600kg, an increase of 29.59% over the control variety Longshu No. 2; in 1995, in the third-generation clonal variety comparison trial, the yield was 2235.25kg, an increase of 23.73% over the control variety; in 1996, in the fourth-generation clonal variety comparison trial, the yield ranked first among all tested varieties at 2604kg, an increase of 16.2% over the control variety Qingshu 168.

3.2 Provincial Regional Trial In 1997, a 6-point trial was set up, with an average yield of 2213.17kg per mu, an increase of 21.12% over the control variety Hushu 202; in 1998, a 5-point trial was set up, with an average yield of 2497.8kg per mu, an increase of 91.34% over the control variety Hushu 202, ranking among the top in yield among all tested varieties.

3.3 Production Trial From 1997 to 1998, a total of 13 point-times were set up in the production trial, with an average yield of 3056.41kg per mu, an increase of 43.69% over the local main varieties (Xiazhai 65, Qingshu 168, Hushu 202). Among them, in the 5-point trial in 1997, the average yield was 3036.3kg per mu, an increase of 36.36%-90.54% over the control variety Qingshu 168, an increase of 53.61% over Hushu 202, and an increase of 105.31% over Xiazhai 65.

4 Cultivation Points

4.1 Land and Crop Rotation Selection Qingshu No. 2 potato has relatively low soil requirements and can be planted in all soils except overly acidic, overly clayey, low-lying, and saline-alkali soils, but the best plots are those with loose, fertile soil, high terrain, deep soil layer, and good drainage and aeration. In field cultivation, it should not be planted after preceding crops of Solanaceae and Cruciferae vegetables, in order to prevent degeneration and yield reduction caused by potato disease infection, so it is advisable to choose crop rotations such as @#@245@#@, corn, legumes, and rapeseed.

4.2 Fine Land Preparation After the preceding crop is harvested, autumn plowing should be carried out as early as possible. In places with severe spring drought, irrigation should be carried out in time after autumn plowing to preserve soil moisture. Organic fertilizer should be applied in combination with autumn plowing. Before spring sowing, fine land preparation should be carried out to preserve soil moisture and ensure emergence.

4.3 Strict Control of Seed Potatoes Selecting tubers with excellent varietal characteristics as seed potatoes is the material basis for increasing potato yield. Seed potatoes should be selected from tubers propagated in seed multiplication fields using high-density seed retention techniques, not infected with the main local viral diseases, well stored, not rotted or sprouted, without mechanical damage or cracks, and possessing the excellent varietal characteristics and shapes of Qingshu No. 2, with uniform size.

4.4 Sprouting and Sowing Pre-sowing sprouting breaks tuber dormancy in advance, shortens the bud growth period, facilitates early emergence, and produces uniform and strong seedlings, with a more significant yield increase effect than direct sowing. Sprouting method: about 20 days before sowing, spread the seed potatoes flat in a room with scattered light, keep the temperature at 10-15°C, and stack the tubers in 2-3 layers. Turn the potato pile once every few days to make the sprouts uniform and thick. However, care should be taken not to sprout for too long. When the sprouts are 1-2cm long, they can be cut and sown.

4.5 Early Sowing at the Right Time and Reasonable Close Planting Early sowing at the right time has an important impact on plant growth and development and subsequent yield formation. The suitable sowing period for Qingshu No. 2 is when the local temperature stably passes 5-7°C. Planting density is closely related to yield. Because Qingshu No. 2 is a late-maturing variety with luxuriant plants, the density should not be too high. Generally, the row spacing is 0.7m, the plant spacing is 0.3m, and it is advisable to maintain 48,000 plants per hectare.

4.6 Heavy Application of Base Fertilizer Heavy application of base fertilizer is beneficial to the early root development of potatoes and the robust growth of seedlings. The base fertilizer should be applied as a mixture of organic fertilizer and chemical fertilizer. Generally, 30000-45000kg of organic fertilizer, 150kg of diammonium phosphate, 75kg of urea, and 75kg of potassium sulfate are applied per hectare, with N:P:K=2:1:10, and each place can increase or decrease as appropriate according to local fertility conditions. When applying base fertilizer, add 30kg of phorate to control underground pests.

4.7 Strengthen Field Management During the potato growth period, the focus of management is to do a good job of intertillage and hilling in the early stage, and pay attention to drainage during waterlogging and irrigation during drought in the later stage, and prevent and control diseases and pests. From emergence to flowering, generally carry out intertillage and hilling three times continuously. After the seedlings are uniform, weed in time. Irrigation should be combined with intertillage and hilling, and it is more appropriate to keep the soil moisture content at 60%-80%. If flood and waterlogging disasters occur during the growth period, drainage and waterlogging prevention should be carried out immediately. At the end of budding, if the plants grow excessively due to excessive water and fertilizer, foliar spraying of 300-10000 times chlormequat or 700-1500 times paclobutrazol can be used for regulation. Qingshu No. 2 is relatively resistant to late blight, but in heavily infested fields, chemical control should be carried out at the early stage of disease onset with 25% metalaxyl 1000-fold solution or 70% thiophanate-methyl wettable powder 800-fold solution.

4.8 Harvesting and Storage Harvest in late September when more than 90% of the field plant stems and leaves have withered and yellowed. Prevent mechanical damage. If the soil is too wet, the harvested tubers should be placed in a ventilated, light-transmitting, cool place for 1-2 days before being put into the cellar. The pile height of tubers in the cellar should not exceed 1m, and the cellar temperature should be kept stable at 1-4°C. In mid-to-late November, the cellar should be turned once to remove diseased tubers and soil, and attention should be paid to preventing freezing, heat, and moisture, so that the tubers always remain in a dormant state.