Morphological and anatomical basis of resistance to blight caused by Botrytis gladiolorum in gladiolus

Morphological and anatomical features of nine genotypes of gladiolus varying in resistance to Botrytis gladiolorum were studied in order to find out the parameter(s) that impart resistance against this devastating disease. The number of stomata was found to be highly positively correlated with disease susceptibility (r=0.96). The resistant cultivars possessed lower number of stomata as compared with the susceptible ones. The lowest number of stomata was recorded in the resistant cultivar Spic'n’Span (156.05/mm²), while it was the highest in susceptible cultivar Sancerre (291.82/mm²). The size of stomata had a moderate positive correlation with disease susceptibility (r=0.50). It was the maximum in the susceptible cultivar Bis-Bis (31.69 µm), whereas the minimum in the resistant cultivar Spic'n’Span (26.43 µm). The stomatal pore size was also moderately correlated with disease susceptibility (r= 0.48). The leaf thickness had a high positive correlation with disease severity (r=0.88). Leaf thickness was the highest (maximum) in susceptible cultivars, viz. Sancerre (390.98 µm) and Bis-Bis (389.96 µm), whereas the lowest (minimum) in the resistant cultivar Spic'n’Span (280.01 µm). Leaf cuticle thickness was highly negatively correlated with disease susceptibility (r=0.91). It was found to be higher in resistant cultivar Spic'n’Span (5.12µm) and in moderately resistant cultivars, viz. Nova Lux (5.27µm) and Jacksonville Gold (4.84µm), whereas it was found to be the lowest in susceptible cultivars Sancerre (3.20µm) and Bis-Bis (3.20µm).