Standardization of screening technique for screening of American cotton germplasm (Gossypium hirsutum L.) against cotton leaf curl disease (CLCuD)

摘要

During 2009, a total of 64 known CLCuD resistant genotypes were screened under artificial conditions through leaf petiole graft technique and under natural epiphytotic conditions. The mean disease incidence under natural epiphytotic conditions was found to be comparatively higher than under artificial conditions. The analysis of the paired t-test revealed that disease incidence at 30 DAS (t=0.036< tabulated t005=2.00) under natural epiphytotic conditions as well as under screen house conditions was statistically at par with each other. However, at 60 DAS (t=9.63>tabulated t005=2.00) and at 90 DAS (t=3.98> tabulated t005=2.00), a significant variation in the disease incidence under natural epiphytotic conditions in comparison to screen house was observed. All the genotypes behaved differently under different set environment as observed with variable reactions. Screening through leaf petiole graft technique for large number of genotypes was found to be cumbersome and unsuccessful. The disease progressions in resistant or moderately resistant genotypes were very slow as compared to the moderately susceptible and susceptible genotypes.