Molecular and biochemical characterization of cotton epicuticular wax in defense against Cotton leaf curl disease (CLCuD)

Background: Gossypium arboreumis resistant to Cotton leaf curl Burewala virus and its cognate Cotton leaf curl Multan betasatellite (CLCuBuVand CLCuMB). However, the G. arboreum wax deficient mutant (GaWM3) issusceptible to CLCuV. Therefore, epicuticular wax was characterized both quantitatively and qualitatively for its role as physical barrier against whitefly mediated viral transmission and co-related with the titer of each viral component (DNA-A, alphasatellite and betasatellite) in plants. Objectives: The hypothesis was the CLCuV titer in cotton is dependent on the amount of wax laid down on plant surface and the wax composition. Results: Analysis of the presence of viral genes, namely alphasatellite, betasatellite and DNA-A, via real-time PCR in cotton species indicated that these genes are detectable in G. hirsutum, G. harknessii and GaWM3, whereas no particle was detected in G. arboreum. Quantitative wax analysis revealed that G. arboreumcontained 183 μg/cm² as compared to GaWM3 with only 95 μg/cm². G. hirsutum and G. harknessii had 130 μg/cm² and 146 μg/cm², respectively. The GC-MS results depicted that Lanceol, cis was 45% in G. harknessii. Heptadecanoic acid was dominant in G. arboreum with 25.6%. GaWM3 had 18% 1,2,-Benenedicarboxylic acid. G. hirsutum contained 25% diisooctyl ester. The whitefly feeding assay with Nile Blue dye showed no color in whiteflies gut fed on G. arboreum. In contrast, color was observed in the rest of whiteflies. Conclusions: From results, it was concluded that reduced quantity as well as absence of (1) 3-trifluoroacetoxytetradecane, (2) 2-piperidinone,n-|4-bromo-n-butyl|, (3) 4-heptafluorobutyroxypentadecane, (4) Silane, trichlorodocosyl-, (5) 6- Octadecenoic acid, methyl ester, and (6) Heptadecanoicacid,16-methyl-,methyl ester in wax could make plants susceptible to CLCuV, infested by whiteflies.