The Heterosis Of CRI 63 And Its Response To High Temperature Stress

As a hybrid variety CRI 63 is widely popularized in the Yangtze River Valley which with strong resistance to disease and insect meanwhile the promotion area has reached more than 2000 million mu.In recent years,continuous high-temperature weather has appeared frequently from July to August which greatly affected the growth and development of cotton,resulting in reduced yield and quality ultimately.However,the mechanism of the formation of heterosis of CRI 63 and the mechanism to high temperature stress are unclear now.The experimental field site is located at the Chinese Academy of Agricultural Sciences in Anyang,Henan,China(36~?06’N and 114~?21’E).In this study,the experiments were conducted using cotton variety CRI 63 as the material with field and pot experiments respectively.The field experiment was analyzed by grid sampling and spatial interpolation based on the spatial statistical method.The formation of heterosis of CRI 63 was obtained through the analysis of the iPAR and growth and development.The differences of the chlorophyll fluorescence parameters、photosynthesis and physiological indexes under the high temperature stress of CRI 63 and their parents were also studied by the pot experiment and then the physiological basis of CRI 63 resistance to high temperature stress was obtained.The main results are as follows:The iPAR variation of CRI 63 hybrids exhibited“V”shapes within the canopy and the distribution of light is even at horizontal and vertical direction within the canopy which is the result of its relatively compact plant type,so the whole population can receive appropriate light radiation.However the male parent with shaded canopy and bad light transmission is not conducive to the boll grow and open in the middle and lower part of the canopy.While,the loose plant type and longer branch of the female parent lead to a shaded canopy in lower part,thus being detrimental to the growth of the boll in this part of the canopy.Finally,the average cottonseed cotton yield of CRI 63 was significantly higher than their parents.Under the high temperature stress,the Chlorophyll fluorescence parameters of CRI 63 including Fv/Fm,Yield,qN,NPQ and ETR were higher than those of their parents.During the high temperature stress,the Fv/Fm of the CRI 63 was above 0.80 all the time and the value of the Yield was between 0.60and 0.65.The value qP decreased first and increase later and the qP value of CRI 63 was higher than their parents continuously.The NPQ value decreased first and then increased with the increase of the time of high temperature stress and change rate was little than their parents.The ETR value has remained above 50,which also is significantly higher than their parents.Under the high temperature stress,the decreasing trend of the chlorophyll-a content and chlorophyll content of the hybrid variety of CRI 63 was more stable than their parents,and degree of declining was smaller;the intercellular carbon dioxide concentration of the CRI 63 was lower than their parents and the net photosynthetic rate CRI 63 was significantly higher than its parent.Under the high temperature stress,the soluble protein content,the content of ABA,and the activity SOD of CRI 63 increase first and then decrease.Furthermore the soluble protein content,ABA content,and the activity was significantly higher than their parents.However the content of MDA of this three varieties was increase continually while the content of MDA of CRI 63 consistently lower than their parents.In summary,the physiological basis of the advantage of CRI 63 are the rational plant type structure and light interception and the higher ability of the resistance to high temperature stress.