Survey of Fusarium species associated with plant debris in South African soils

Abstract

Fusarium species were isolated from plant debris in 29 composite soil samples from 22 locations representing the major agricultural areas and vegetation types of South Africa. The survey provided qualitative and quantitative information on the occurrence, distribution and ecology of Fusarium spp. in South African soils. The results obtained with the isolation and enumeration methods used were highly reproducible in two independent laboratories. Altogether 2 425 Fusarium isolates were recovered, representing 23 species and 6 undescribed taxa. Two Fusarium spp., F. tricinctum (Corda) Sacc. and F. camptoceras Wollenw. & Reinking, were recorded for the first time in South Africa. The five most prevalent Fusarium spp. which comprised 76% of the isolates obtained were F. oxysporum Schlecht. emend. Snyd. & Hans., F. solani (Mart.) Appel & Wollenw. emend. Snyd. & Hans., F. equiseti (Corda) Sacc., F. nygamai Burgess & Trimboli, and F. compactum (Wollenw.) Gordon. Three of these species (F. oxysporum, F. solani and F. equiseti) occurred significantly more frequently in cultivated than in undisturbed soils. The reverse was true for F. nygamai. The incidence of F. compactum did not differ significantly in cultivated and undisturbed soils. The incidences of F. solani and F. compactum were significantly higher in soils from low altitude, subtropical areas in the summer rainfall region than from other climatic areas. Fusarium-spesies is geïsoleer uit plantreste in 29 saamgestelde grondmonsters vanaf 22 lokaliteite verteen-woordigend van die hoof landboukundige areas en plantegroeitipes van Suid-Afrika. Die opname het kwalitatiewe en kwantitatiewe inligting oor die voorkoms, verspreiding en ekologie van Fusarium-spp. in Suid-Afrikaanse gronde beskikbaar gestel. Die resultate wat verkry is met die isolasie- en enumerasie-metodes wat gebruik is, was goed vergelykbaar in twee onafhanklike laboratoriums. ’n Totaal van 2 425 Fusarium-isolate, verteenwoordigend van 23 spesies en 6 onbeskrewe taksa, is verkry. Twee Fusarium-spp., F. tricinctum (Corda) Sacc. en F. camptoceras Wollenw. & Reinking, is vir die eerste keer in Suid-Afrika aangeteken. Die vyf mees algemene Fusarium-spp. wat 76% van die totale aantal isolate behels het, was F. oxysporum Schlecht. emend. Snyd. & Hans., F. solani (Mart.) Appel & Wollenw. emend. Snyd. & Hans., F. equiseti (Corda) Sacc., F. nygamai Burgess & Trimboli, en F. compactum (Wollenw.) Gordon. Drie van hierdie spesies (F. oxysporum, F. solani en F. equiseti) het betekenisvol meer algemeen voorgekom in bewerkte as onversteurde grond, die teenoorgestelde was waar in die geval van F. nygamai, en die voorkoms van F. compactum het nie betekenisvol verskil nie. Die voorkoms van F. solani en F. compactum was betekenisvol hoër in gronde vanaf laagliggende, subtropiese gebiede in die somerreënvalstreek as in ander klimatologiese gebiede.