Soil receptivity and host - pathogen dynamics in soils naturally infested with Fusarium oxysporum f. sp. cubense, the cause of Panama disease in bananas

Abstract

Disease severity associated with the pathogen Fusarium oxysporum is generally thought to be proportional to the population of fungal propagules in the soil. However, results from studies using naturally infested soil are contradictory, implicating host predisposition to disease. In this study, soil was amended with chicken manure to investigate the interdependence between the activity and invasiveness of the pathogen, and the incidence of Panama disease in susceptible banana plantlets. Two soil types naturally infested with either race 1 or race 4 of the pathogen, and cultivars Lady finger and Grande Naine, were used. Pathogen activity was measured by burying root tip segments for 5 days, then calculating the frequency of isolation of Fusarium from the segments. Pathogen invasion was measured by transplanting banana plantlets into trays of amended and unamended soil for 4 weeks, then calculating the frequency of recovery of Fusarium from each pseudostem. Amending both soil types with chicken manure enhanced both pathogen invasion and disease incidence. However, pathogen activity was not correlated with either parameter. We postulate that the addition of chicken manure is predisposing banana plantlets to Panama disease, by reducing the efficacy of the host wound response.

A foliar rating system for comparing the resistance of banana cultivars grown as tissue-cultured plantlets in the laboratory to Fusarium wilt

“…Lady Finger growing on two commercial properties near Currumbin (28°15′S, 153°26′E) in south-east Queensland, Australia. The two properties were known to be infested with race 1 of the pathogen, with only one Vegetative Compatibility Group having been detected (VCG 0125, Pittaway et al 1999). Before use, the soil was coarsely sieved (1 cm 2 grid) to remove plant debris and to break larger soil aggregates.…”

“…The frequency of invasion of the pseudostem of each plantlet by Foc was calculated using the method of Pittaway et al (1999) with the following modification. After surface sterilisation, the pseudostem/corm tissue was divided into three horizontal regions.…”

“…The results of other laboratory assays have been questioned due to the use of unrealistically high inoculum levels to challenge plantlets (Pegg and Langdon 1987;Buddenhagen 1990). Recently, Pittaway et al (1999) established that amending field soil naturally infested with Foc with chicken manure increased the severity of Panama disease. The increase in disease severity relative to the unamended control could be reproduced in susceptible plantlets grown in soils naturally infested with either race 1 or race 4 of the pathogen.…”

Effect of organic amendments and solarisation on Fusarium wilt in susceptible banana plantlets, transplanted into naturally infested soil

“…The soil was amended at a ratio of 9:1 (v :v) field soil and aged chicken manure (Pittaway et al 1999). Hardwood sawdust (predominantly Eucalyptus maculata and E. crebra) was collected from a local sawmill and composted in a 1-m 3 retaining box for 16 weeks.…”

“…In a previous study, amending soil naturally infested with Foc with chicken manure was found to increase wilt disease severity in susceptible bananas in the absence of any change in the activity of the pathogen population in the soil (Pittaway et al 1999). In this study the chicken manure effect was used as a reference, to confirm the sensitivity of the activity and invasion bioassays in monitoring changes in pathogen activity and disease incidence, respectively.…”