CHEMICALLY-INDUCED CUTICLE MUTATION AFFECTING EPIDERMAL CONDUCTANCE TO WATER-VAPOR AND DISEASE SUSCEPTIBILITY IN SORGHUM-BICOLOR (L) MOENCH

Analysis of Sorghum bicolor bloomless (bm) mutants with altered epicut icular wax (EW) structure uncovered a mutation affecting both EW and c uticle deposition. The cuticle of mutant bm-22 was about 60% thinner a nd approximately one-fifth the weight of the wild-type parent P954035 (WT-P954035) cuticles. Reduced cuticle deposition was associated with increased epidermal conductance to water vapor. The reduction in EW an d cuticle deposition increased susceptibility to the fungal pathogen E xserohilum turcicum. Evidence suggests that this recessive mutation oc curs at a single locus with pleiotropic effects. The independently occ urring gene mutations of bm-2, bm-6, bm-22, and bm-33 are allelic. The se chemically induced mutants had essentially identical EW structure, water loss, and cuticle deposition. Furthermore, 138 F-2 plants from a bm-22 x WT-P954035 backcross showed no recombination of these traits. This unique mutation in a near-isogenic background provides a useful biological system to examine plant cuticle biosynthesis, physiology, a nd function.