Incidence and severity of cotton leaf curl virus disease on different BG II hybrids and its effect on the yield and quality of cotton crop

Aim: To understand the effect of Cotton Leaf Curl Disease incidence and severity at various crop growth stages on Bollgaurd-II cotton hybrids having different levels of susceptibility and resistance and its effect on, seed cotton yield and fibre quality. Methodology: The effect of cotton leaf curl disease (CLCuD) incidence, severity and its progress on highly resistant to susceptible cultivars was compared. The loss of seed cotton yield (SCY) corresponding to CLCuD incidence at 80 DAS, 81-110 DAS, 111-140 DAS was estimated separately in each hybrid. The loss of fibre quality corresponding to CLCuD incidence at seven different stages, i.e., 50 to 140 days after sowing (DAS) was also calculated. Results: The highest relative area under disease progress curve (AUDPC) values of PDI were observed in Ankur 3028 (100%) and Ankur Jai BG II (83%), while the lowest values were recorded in highly resistant hybrids Yuva-841-2 (4.6%) and Bunty 2113-2 (13.8%). When the disease appeared up to 80 DAS compared to 110, 140 DAS the reduction range in SCY (4.6-62.4%), fibre length (23.9-29.9%), strength (21.4-30.1%) and uniformity (62.5-83%) was recorded to be higher in susceptible hybrids. The fibre length, strength, and uniformity were reduced in diseased plant (25.9 mm, 24.4 g/tex, 68.2%) when incidence took place at 50 DAS compared to disease-free plants (27.6mm, 25.9 g/tex, 72.9%). However, reduction in SCY, fiber length, fiber strength and uniformity at 80 DAS varied with respect to hybrid and their resistance category. Interpretation: These results provide the basis to prove the hypothesis that the yield loss is associated with the stage of CLCuD incidence and its severity in cotton hybrids with different levels of resistance as well as its genetic potential of a particular cotton cultivar. However, the extent of yield reduction within the resistant or susceptible category is also dependent on the yield potential of a particular cultivar. Thus, breeders must consider both the criteria-lower PDI /AUDPC and higher productivity to select high yielding cotton lines. Key words: Cotton, Disease index, Leaf Curl Disease, Virus