Relationship of tissue structure and resistance to Verticillium wilt in cotton

Verticillium dahliae Kleb.harms seriously production of cotton.Thirty-one cotton cultivars with different resistance were used in the greenhouse,aimed to analyse the resistance to Verticilium wilt in cotton.Tissue structure was studied to realize the resistance mechanism of cotton to Verticilium wilt using the method of root scanning and paraffin slice.The results showed that:the density of roots which absorbed water and nutrition had correlation with the disease index,r=0.923.There was significant difference in total root length,total projective area,total surface area and absorbable root length density among the resistance,tolerance and susceptible cultivars.But the difference between those of the tolerance and susceptible cultivars were not significant.The density of xylem parenchyma cells and vessel numbers in root and stem of resistant cultivars were the biggest,that of tolerant cultivars were the next and that of susceptible ones were the least,but the diameter of vessels were contrary.The absorbable root length density,density of xylem parenchyma cells and vessel numbers in root and stem can be used as measuring index of resistance to verticillium wilt in cotton.