Fusarium species that cause corn stalk rot in the Ubaté valley of Cundinamarca, Colombia

Abstract

In recent years, corn (Zea mays L.) crops in the Colombian cold tropics located in the Ubaté valley in Cundinamarca have been affected by stalk rot with incidences up to 40%. Despite the importance of this disease, accurate diagnosis has not been conducted. The objectives of the study were to determine the causal agents of corn lodging associated with stalk rot in this corn-producing region and describe the symptoms of the disease. Two plots with stalk rot reported in the municipality of Simijaca in July 2016 were sown with the regional varieties Simijaca and Sogamoso. Plants were randomly inspected on a monthly basis for describing disease symptoms and isolating the pathogen. The Fusarium species isolated were morphologically and molecularly identified and pathogenicity tests were conducted. The disease was detected at early plant developmental stages with the combination of chlorosis, leaf anthocyanosis, and dwarfism as the main symptoms in the two corn varieties evaluated. Crown and node necrosis in longitudinal sections of the stalk and purple colorations in the crown, nodes and internodes of plants were observed 90 d after sowing. Finally, lodging occurred at any phenological stage of the crop. Fusarium spp. were isolated in all stages of plant development. Fusarium species were identified as F. graminearum in the Fusarium graminearum species complex and F. subglutinans in the Fusarium fujikuroi species complex, which have cold-climate production zones as their ecological niche. Pathogenicity tests confirmed F. graminearum and F. subglutinans as the causal agents of stalk rot in the regional corn variety Simijaca in the Ubate valley in Cundinamarca.