Association of stomatal frequency and morphology in Lycopersicon species with resistance to Xanthomonas campestris pv. vesicatoria

Abstract

Study of the stomata and leaf epidermis of eight Lycopersicon species has revealed a relationship between frequency of stomata, stomatal size and some morphological leaf characteristics, and resistance to bacterial leaf spot caused by Xanthomonas campestris pv. vesicatoria. Significant correlations were found between the stomatal frequency in both adaxial and abaxial leaf epidermis and the number of bacterial lesions per leaf area (r= 0.70 and 0.68, respectively) and the frequency of stomata in both adaxial and abaxial epidermis and disease incidence (percentage of diseased plants) (r=0.87 and 0.80, respectively) for all the Lycopersicon species and one hybrid tested. A correlation was also found between disease incidence and number of bacterial lesions per leaf area (r= 0.85). The length and width of stomata were correlated with frequency of stomata in adaxial and abaxial epidermis (r= 0.85, 0.75, 0.89 and 0.90, respectively). The stomatal width was correlated with the number of bacterial lesions per cm2 (r=0.82; P= 0.0065). Scanning electron microscopic studies of the leaf surface and stomata indicated that other morphological features such as the raised stomatal complex in L. hirsutum and persistent, hydrophobic waxy coating of the epidermis in L. peruvianum may also be relevant in disease response.