China'S Cotton Breeding Has Experienced Several Variety Changes, And The Water Demand Characteristics Of Cotton At Flowering And Boll Setting Stages

Taking the breeding history of Xuzhou Agricultural Science Research Institute as an example, it has gone through about four stages from the Republic of China to the present, which occurred in the 1970s, 70-80s, 80-90s and after the 1990s. The breeding methods of these four stages are interdependent, and the purpose is to combine systematic breeding and cross breeding, then create material variation, and then select and identify breeding materials with systematic breeding methods to achieve ideal results 　

Cotton breeding in China has gone through several variety changes. 1. Taking the breeding history of Xuzhou Agricultural Science Research Institute as an example, Xuzhou Agricultural Science Research Institute has gone through about four stages from the Republic of China to the present. The first stage occurred before the 1970s, when it mainly focused on systematic selection; The 70s and 80s are the second stage, which is due to the fact that China's cotton breeding has experienced several variety changes, and the water demand characteristics of cotton at flowering and boll stage

Taking the breeding history of Xuzhou Agricultural Science Research Institute as an example, it has gone through about four stages from the Republic of China to the present, which occurred in the 1970s, 70-80s, 80-90s and after the 1990s. The breeding methods of these four stages are interdependent, and the purpose is to combine systematic breeding and cross breeding, then create material variation, and then select and identify breeding materials with systematic breeding methods to achieve ideal results.

　 1、 Cotton breeding in China has experienced several variety changes

1. Taking the breeding history of Xuzhou Institute of Agricultural Sciences as an example, Xuzhou Institute of Agricultural Sciences has gone through about four stages from the Republic of China to the present. The first stage occurred before the 1970s, when it mainly focused on systematic breeding; 70s and 80s is the second stage, which is the coexistence stage of systematic breeding and hybrid breeding; The third stage, which was dominated by cross breeding, occurred in the 1980s and 1990s; Since the 1990s, it has been the fourth stage. It is characterized by the breeding of new transgenic cotton bollworm resistant varieties, and simultaneously carries out heterosis utilization and cross breeding.

2. The breeding methods of these four stages complement each other, combining systematic breeding and cross breeding, creating material variation by means of cross breeding, and then selecting and identifying breeding materials by means of systematic breeding to achieve twice the result with half the effort.

3. From the Republic of China to the 1970s, due to the limitations of the times, breeding was the main focus. At this stage, it was emphasized that the basic materials to be selected should have a high starting point. Under the guidance of the breeding policy of selecting the best among the many and selecting the best among the best, new varieties could be quickly selected. However, due to the narrow genetic basis of systematic breeding, the variation resources for selection were only formed naturally, so there was a lack of certain controllability, In particular, the variation of quality and stress resistance cannot meet the requirements.

4. Since the 1980s, cross breeding has been promoted to a certain height. Various methods have been used to constantly enrich the genetic basis, accumulate variation resources, allow gene recombination and accumulation, and constantly break the negative correlation of major economic traits caused by gene linkage. Then, these excellent mutations were selected and preserved by the hybrid plus systematic breeding method, and good results were achieved.

　 2、 Water demand characteristics of cotton at flowering and boll setting stage

1. What are the characteristics of water demand of cotton at flowering and boll setting stage

Flowering and bolling period is a period of huge water demand of cotton in its lifetime, which accounts for about 45-65% of the total water demand of cotton in its lifetime, while the water absorption per mu of cotton field per day and night is 2.5-3.0 cubic meters.

2. How to water cotton during flowering and boll setting

(1) Look at the sky: Take planting cotton in Shandong as an example. During the rainy season, cotton fields usually do not need irrigation, but ordinary cotton fields should be watered if there is no rain for about 15 days, and high-yield cotton fields should also be watered if there is no rain for about 10 days.

(2) Ground observation: because the suitable soil moisture content of cotton field at flowering and boll stage is 70-80% of the maximum field water capacity, when the soil moisture content of 20-40cm depth is lower than 60% of the maximum field water capacity, watering is required.

(3) Seedling inspection: when the cotton plant grows slowly, the proportion of red stems increases, the leaves wilt at noon, the leaf color changes from the normal upper four leaves to the black upper and lower leaves, the leaves become thicker and smaller, the fruit branches extend slowly, and the flowering speed increases, watering is required.

(4) Precautions: When irrigating the cotton field, the relationship between water and air should be well coordinated. The root system should not only absorb enough water, but also store air in the soil pores to ensure that the root system can breathe normally. It is recommended to use ditch irrigation instead of flooding. When there is water in the cotton field, it should be discharged in time.