Morphogenetic Alterations of Alternaria alternata Exposed to Dicarboximide Fungicide, Iprodione

Abstract

Fungicide-resistant Alternaria alternata impede the practical control of the Alternaria diseases in crop fields. This study aimed to investigate cytological fungicide resistance mechanisms of A. alternata against dicarboximide fungicide iprodione. A. alternata isolated from cactus brown spot was cultured on potato-dextrose agar (PDA) with or without iprodione, and the fungal cultures with different growth characteristics from no, initial and full growth were observed by light and electron microscopy. Mycelia began to grow from one day after incubation (DAI) and continued to be in full growth (control-growth, Con-G) on PDA without fungicide, while on PDA with iprodione, no fungal growth (iprodione-no growth, Ipr-N) occurred for the first 3 DAI, but once the initial growth (iprodione-initial growth, Ipr-I) began at 4–5 DAI, the colonies grew and expanded continuously to be in full growth (iprodione-growth, Ipr-G), suggesting Ipr-I may be a turning moment of the morphogenetic changes resisting fungicidal toxicity. Con-G formed multicellular conidia with cell walls and septa and intact dense cytoplasm. In Ipr-N, fungal sporulation was inhibited by forming mostly undeveloped unicellular conidia with degraded and necrotic cytoplasm. However, in Ipr-I, conspicuous cellular changes occurred during sporulation by forming multicellular conidia with double layered (thickened) cell walls and accumulation of proliferated lipid bodies in the conidial cytoplasm, which may inhibit the penetration of the fungicide into conidial cells, reducing fungicide-associated toxicity, and may be utilized as energy and nutritional sources, respectively, for the further fungal growth to form mature colonies as in Ipr-G that formed multicellular conidia with cell walls and intact cytoplasm with lipid bodies as in Con-G.

New Recombinant Antimicrobial Peptides Confer Resistance to Fungal Pathogens in Tobacco Plants

“…Despite application of hazardous chemicals to prevent the colonization and growth of plant pathogens ( Hahn, 2014 ; Drenth and Guest, 2016 ), the appearance of resistant isolates of devastating pathogens, especially fungi and oomycetes challenge the use of fungicides ( Nicot et al., 2016 ). For instance, it has recently been documented that species belonging to Alternaria and Phoma have developed resistance against QoI or strobilurins and benzimidazole group of fungicides, respectively ( Van de Graaf et al., 2003 ; Karaoglanidis et al., 2011 ; Kim et al., 2017 ), suggesting either new classes of fungicides must be designed or different approaches should be taken to overcome emerging plant pathogens.…”

Survival of pathogens after dormancy in apple tree twigs indicates potential risk as source of inoculum

“…conidia are generally thick and formed of several cells, which could also be related to the survival even after winter treatments. This fact was evidenced by Kim, Lee, and Kim (2017), who found A. alternata isolates resistant to the fungicide iprodione. The isolates showed visible cellular alterations during sporulation, forming multicellular conidia with thickened double-celled walls and accumulation of lipidic bodies in the cytoplasm, which can inhibit fungicide penetration into conidial cells, reducing fungicide efficiency, and used as energy and nutritional sources by the fungus.…”

Effect of Ephedra alanda Extract against Alternaria alternata

“…In plants, Alternaria alternata appears as a phytopathogenic fungus causing various symptoms, black spots, rot, rust, etc. on the diff erent organs of the plant [13].…”