Soybean bud proliferation and seed pod abortion disease in Iran: associated pathogens, epidemiology, transmission and management perspectives

Soybean is one of the world's most important agricultural crops and a major source of plant-based protein and edible oil. In recent years, phytoplasma-associated diseases have emerged as significant threats to sustainable soybean production. Among them, soybean bud proliferation and seed pod abortion disease (SbpSpa), first reported in Iran, has gained increasing attention as a novel and economically important disease. SbpSpa is characterized by abnormal bud proliferation, flower malformations, clustered reproductive structures, and severe pod abortion, ultimately leading to substantial yield losses. Molecular analyses based on nested PCR and 16S rRNA gene sequencing have identified the presence of ‘Candidatus Phytoplasma trifolii’ strains. Epidemiological studies have confirmed the involvement of Creontiades pallidus as insect vector and of Salix alba and various weed species as possible alternative hosts. Evidence suggesting possible seed transmission further highlights the epidemiological complexity and quarantine importance of this disease that is primarily distributed in northern Iran, especially in Golestan and Mazandaran provinces, where it has caused significant economic losses in some growing seasons. Environmental conditions, insect vector abundance, and the presence of reservoir hosts play key roles in disease development and spread. The absence of resistant cultivars and the complexity of the disease cycle, involving multiple biotic and abiotic factors, make management particularly challenging.