Role of various leaf physiological characteristics in resistance against black spot disease in rose

Abstract

Black spot disease remains a significant threat to rose cultivation. While genetic resistance to black spot is well documented, the underlying physiological mechanisms often vary. In order to identify the key physiological determinants of black spot resistance, eight selected genotypes ranging from highly susceptible to highly resistant were investigated for various physiological characteristics viz., number and size of stomata, gas exchange parameters, leaf thickness and epicuticular wax content. Our findings reveal that the "Highly Resistant" genotype, Knock Out, possesses a unique combination of maximum leaf thickness (190.67 μm), the lowest stomatal conductance (0.26 (mol (H2O) m-2 s-1) and high epicuticular wax (254.13 μg/cm2). This suggests that resistance is a synergistic result of structural barriers and regulated gas exchange.