Maize Stalk Rot Caused by Lasiodiplodia theobromae and L. iraniensis in South Sulawesi, Indonesia

Abstract

Maize diseases represent a major threat to global maize production. Symptoms of stalk rot and plant decline have been observed in maize crops in Sidenreng Rappang (Sidrap) Regency, in South Sulawesi, Indonesia. The causal agent was identified through evaluation of morphological characteristics, DNA sequences, and phylogenetic analyses. Two fungal isolates from infected stalks indicated morphologically that they resembled Lasiodiplodia species. Hyaline, ovoid and aseptate immature and ovoid to ellipsoidal mature conidia of the isolates indicated that the isolates were Lasiodiplodia species. The ITS and EF1 α sequences confirmed that the isolates were Lasiodiplodia theobromae and L. iraniensis . The initial pathogenicity assessment using a leaf disk bioassay demonstrated that L . theobromae and L . iraniensis induced necrotic lesions. Subsequent pathogenicity tests confirmed that both isolates caused necrotic lesions on maize stalks, which were characterized by dark brown to black discoloration of vascular tissues. These symptoms were consistent with those observed in natural field infections. The pathogenicity test suggested that Lasiodiplodia theobromae isolate was more virulent than L . iraniensis in infecting maize stalks. To our knowledge, the study finding is the first record of L . theobromae and L . iraniensis as the causal agents of stalk rot disease in maize plants in Indonesia. The emergence of these pathogens emphasizes the need for effective disease management strategies in maize cultivation to prevent further losses and limit their dissemination.

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