Morphological and Molecular Characterization of Bacterial Pathogens Associated with Leaf Mottle of Sunflower in Northern Kazakhstan

Abstract

Leaf mottle is a serious disease in the growth and development of sunflowers (Helianthus annuus L.) that can affect their quality and yield. Over the past years, the North Kazakhstan region, a sunflower-producing area in Kazakhstan, has been seriously affected by leaf mottle. Since 2021, symptomatic leaves have been collected from production areas of this base to determine the pathogens of sunflower foliar diseases. One hundred bacterial strains were isolated, and 2 genera and 5 species were identified based on morphological characteristics, molecular genetics and phylogenetic analysis (16S gene region). The genus Bacillus was represented by 4 species-B. subtilis, B. megaterium, B. amyloliquefaciens and B. flexus. The genus Paenibacillus is represented by one species, P. peoriae. Pathogenicity experiments showed that B. subtilis, B. megaterium, B. flexus and P. peoriae could cause disease symptoms. However, B. flexus leaves are highly similar to infected leaves observed under natural conditions in the field. Therefore, these bacterial isolates are considered to be the primary pathogens causing sunflower leaf mottle, and B. flexus was the most common and virulent pathogen in this study. In addition, this is the first study of B. megaterium, B. flexus and P. peoriae as pathogens associated with sunflower leaf mottle in Kazakhstan.