Fusarium and Neocosmospora Species Associated with Rot of Cactaceae and Other Succulent Plants

Abstract

Infections by Fusarium and Fusarium-like species on cacti and other succulent plants cause the syndrome known as Fusarium dry rot and soft rot. There are only few records of Fusarium species as pathogens of cacti and other succulent plants from Iran. The objective of this study was the identification and characterization of fusarioid species recovered from ornamental succulents in Shiraz County, Iran. Three fusarioid species, including F. oxysporum, F. proliferatum, and Neocosmospora falciformis (formerly F. falciforme), were recovered from 29 diverse species of cacti and other succulents with symptoms of Fusarium dry rot and soft rot. The three fungal species were identified on the basis of morphological characters and the phylogenetic analysis of the translation elongation factor1-α (tef1) nuclear gene. The F. oxysporum isolates were identified as F. oxysporum f. sp. opuntiarum. The pathogenicity of the three fusarioid species was tested on a range of economically important ornamental succulents, mostly in the Cactaceae family. The three species showed a broad host spectrum and induced different types of symptoms on inoculated plants, including soft and dry rot, chlorosis, necrotic spots, wilt, drying, root and crown rot. This is the first report of N. falciformis as a pathogen of succulent plants worldwide.

Keywords: Cactaceae; Fusarium oxysporum f. sp. opuntiarum; Fusarium proliferatum; Nectriaceae; Neocosmospora falciformis; cross-inoculations; host range; pathogenicity; phylogenetic analysis; tef1 gene.

Figure 2

Phylogenetic relationships of Neocosmospora falciformis isolates recovered from Shiraz County greenhouses with other N. falcifomis isolates and 56 diverse Neocosmospora species (see Sandoval-Denis et al. 2019) based on Bayesian analysis of translation elongation factor1-α (tef1) sequences. Numbers above the branches represent the posterior probability based on Bayesian analysis. Isolates retrieved from succulent plants in Iran are shown in bold.

Figure 3

Phylogenetic relationships of Fusarium species recovered from Shiraz County greenhouses with 24 Fusarium species based on Bayesian analysis of translation elongation factor1-α (tef1) sequences. Numbers above the branches represent the posterior probability based on Bayesian analysis. Isolates retrieved from succulent plants in Iran are shown in bold (or arrows point at isolates retrieved form succulent plants in Iran).

Figure 1

Colony morphology of (A) Neocosmospora falciformis (isolate FNol01); (B) Fusarium oxysporum f. sp. opuntiarum (isolate OEcg42); and (C) Fusarium proliferatum (isolate PEcg29) from succulent plants; front (left) and back (right) side after 5 days incubation on PDA at 25 °C in the dark.

Figure 4

Symptoms induced by artificial inoculation of Neocosmospora falciformis on various succulent plants. (A) Crown rot on Ferocactus macrodiscus; (B) root and crown rot on Mammillaria bernalensis; (C) brown rot on Mammillaria prolifera; (D) root and crown rot on Mammillaria gracilis; (E) root and stem rot on Astrophytum asterias; (F) rotting, yellowing, and black spots on Mammillaria spinosissima; (G) crown rot on Opuntia ficus-indica; (H) chlorosis on Ferocactus macrodiscus; (I) chlorosis on Ferocactus glaucescens; (J) black spots on Echinocactus grusonii; (K) necrosis and black spots on the crown of Mammillaria bernalensis; and (L) root and crown rot on Aeonium arboreum.

Figure 5

Symptoms induced by artificial inoculation of Fusarium oxysporum f. sp. opuntiarum on different succulent plants. (A–C) necrosis and yellowing on Echinocactus grusonii, Mammillaria spinosissima, and Opuntia fragilis, respectively; (D) discoloration and rotting on Hamatocactus setispinus (syn. Thelocactus setispinus); (E) root and crown rot with yellowing on Ferocactus emoryi; (F) rot and death of Echinocactus grusonii; (G) yellowing, discoloration, and crown rot on Stenocactus multicostatus; (H) root and crown rot as well as leaf dessication on Braunsia apiculata; (I) crown rot and yellowing on Mammillaria jaliscana; (J) root and crown rot on Mammillaria bernalensis; (K) root and crown rot on Sedum reflexum “Angelina”; (L) root and crown rot, yellowing, and necrotic area on Mammillaria gracilis; (M) yellowing and chlorosis on Astrophytum myriostigma; (N) root rot on Echinocactus grusonii; (O) crown rot, yellowing, and chlorosis on Mammillaria matudae; (P) dark-brown spots and soft rot on Carnegiea polylopha (syn. Neobuxbamia polylopha); (Q) soft rot on Astrophytum asterias; (R) black spots and stripes on Carnegiea polylopha; (S) root and crown rot on Aeonium arboreum; (T) black spots on crown and stem of Echinocactus grusonii; (U) root and crown rot, yellowing, and chlorosis on Astrophytum myriostigma; (V) chlorosis on Ferocactus macrodiscus; (W) root rot and drying on Sempervivum tectorum; and (X) root and crown rot as well as yellowing on Ferocactus emoryi.

Figure 6

Symptoms induced by artificial inoculation of Fusarium proliferatum on different succulent plants. (A) rotting, yellowing, and girdling of the basal stem in Mammillaria prolifera; (B) root and crown rot on Mammillaria gracilis; (C) plant decline and death on Mammillaria pottsii; (D) crown rot and yellowing on Cephalocereus euphorbioides; (E) black spots on crown and stem of Echinocactus grusonii; (F) crown rot and yellowing on Astrophytum myriostigma; (G) crown rot and yellowing on Mammillaria gracilis; (H) basal sunken lesion and root rot in Hamatocactus setispinus (syn. Thelocactus setispinus); (I) plant decline from the top of the stem on Cereus jamacaru; (J) crown rot and yellowing on Echinocactus grusonii; (K)crown rot and yellowing on Mammillaria jaliscana; and (L) chlorosis and soft brown spots on Astrophytum myriostigma.