| Xinjiang is China’s largest commodity cotton production base,the total output of 83.8% of the country,cotton planting level of mechanization and scale has reached the forefront of the country,including the corps of mechanized harvesting area of more than 90%,machine cotton has become an inevitable trend of cotton production.Cotton defoliation is one of the important links of mechanical cotton picking.The quality of cotton defoliation directly affects the clean rate and impurity rate,and then affects the processing quality of raw cotton.In recent years,different varieties of defoliating agent,different application techniques,different operation machinery,different cultivation modes and different processing methods have been applied to improve the quality of machine-picked cotton.However,planting suitable varieties of machine-picked cotton is still the most effective way to improve the quality of machine-picked cotton.In this study,the sensitivity of machine-picked upland cotton varieties(lines)and defoliant in this reclamation area was studied to assist the decision-making of machine-picked cotton varieties,to clarify the performance traits and evaluation indexes of defoliant sensitivity,and to provide germplasm resources and theoretical basis for the breeding of machine-picked special varieties.The results of this experiment are as follows:1 Effects of defoliating agent on 6 cotton varietiesThe defoliation rate,floc opening rate,fiber quality,yield and yield characters of tahe 2,Xinluzhong82,Yuanmian 13305,Xinluzhong 85,Xinluzhong 78 and Zhongmiansuo 96 A were compared.It was found that the defoliation rate,fruit branch and leaf branch defoliation rate,floc production rate,abscisic acid content and malondialdehyde content of cotton varieties were significantly increased by spraying defoliation agent.Fiber quality and yield composition of cotton were not significantly affected.Different spraying time of defoliating agent will affect the efficacy of defoliating agent.In the appropriate range,the higher the ambient temperature,the greater the effect of defoliating agent on cotton.2 Sequencing of defoliation sensitivity of alar main cultivars1.According to the defoliation rate of 20 d,tahe 2 > Xinluzhong 85 > Yuanmian 13305> Zhongmian Suo 96A> Xinluzhong 82 > Xinluzhong 78.2.According to the batting rate of 20 d,tahe 2 > Yuanmian-13305 > Xinluzhong 78 > Xinluzhong 82 >Xinluzhong 85 > Zhongmiansuo 96 A.3.The comprehensive score of defoliant sensitivity was ranked by principal component analysis: Tahe2 > Yuanmian-13305 > Zhongmiansuo 96A> Xinluzhong 82 > Xinluzhong 85 > Xinluzhong 78.3.Explore the related characters and evaluation indexes of defoliant sensitivityLogistic growth function model was used to fit the defoliation process of each treatment.We found that the maximum growth rate of defoliation rate appeared from the 4th day to the 7th day,plus the duration of vigorous defoliation period.We suggested that the defoliation rate of different varieties could be appropriately extended from the 4th day to the 7th day for a more comprehensive evaluation.It can also be found from the fitted table that,compared with the control with clean water,the maximum defoliation rate of each variety after fitting with defoliating agent was greatly increased and there was a significant difference.Therefore,in the absence of the final defoliation rate data,we can obtain the maximum defoliation rate by fitting to evaluate the material’s defoliation agent sensitivity.Through correlation analysis,there was a significant positive correlation between cotton defoliation rate and boll weight,and a significant positive correlation between cotton flossing rate and abscisic acid content.Through principal component analysis of defoliating agent related indexes,we found that the index weight of more than 5% are abscisic acid,15 d defoliation rate,10 d defoliation rate,20 d defoliation rate,5d defoliation rate,elongation,specific breaking strength,single boll weight,20 d flocculation rate,malondialdehyde content..4.Screening of defoliant sensitive materialsThe defoliation rate of 5-10 d was used as the evaluation index of defoliation sensitive materials.Cluster analysis was carried out on 45 machine-picked cotton varieties(lines)in Alar Reclamation area to screen out that they were sensitive to defoliation agents.And the floc production rate is more than 90% of the materials nongken 3,Linjin Ken 1643,Nongken 2,Tahe 2,Xinluzhong 78,Xinluzhong 85,Yuanmian13305,Xinluzhong 82.The flocculation rate of nongken 3,Xinluzhong 78 and Xinluzhong 85 was greater than 95%,which provided germplasm resources for breeding new varieties of upland cotton suitable for defoliation and mechanical picking. |
