Die Biologie van enkele fungussoorte wat by die kommersiele verbouing van Agaricus bisporus (Lange) Imbach in Suid-Afrika probleme skep

Abstract

It is important to understand the biology of detrimental fungi in order to exploit possible weaknesses in their armour by means of suitable control measures. The fact that so little is known about the Chromelosporium investigation. biology of the two mushroom antagonists, fulvum and Verticillium fungicola, prompted this Both fungi were able to utilize a broad range of carbon sources but exhibited relatively poor growth on cellulose. A variety of nitrogen sources were also utilized, and a number of organic nitrogen sources in particular, resulted in good growth. Both fungi are mesophiles. The optimum temperature for f.fulvum growth was between 28 and 32°c while sporulation was best at 28°c. For y.fungicola, growth and sporulation were both optimal between 22 and 24°c. As a result of this investigation doubt arose regarding the rationale of distinguishing two y.fungicola varieties on the basis of their temperature requirements only. C.fulvum growth was significantly poorer in the dark than in the light, while for sporulation, the opposite held true. Alternating light and darkness resulted in better sporulation than either light or darkness. Contrary to the accepted norm, red light apparently had a more pronounced effect on sporulation than light from the blue part of the spectrum. Light had little effect on vegetative growth of y.fungicola, but under conditions of darkness, sporulation was much poorer than under any of the light treatments applied. The pH optimum for f.fulvum, as well as for y.fungicola growth, was situated slightly towards the acid side of neutral. C.fulvum did not grow in a medium containing Mcilvaine's buffer, but this inhibition could not be ascribed solely to the presence of the citric acid in the buffer. Both fungi are obligate aerobes. From these results, there does not seem to be anything exceptional in the physiological requirements of any one of the two fungi. Dichobotrys abundance can easily be mistaken for C.fulvum on mushroom beds. In vitro however, none of these two fungi had any inhibiting effect on mycelial mushroom growth. Agaricus bisporus on the other hand, seemed to inhibit C.fulvum. f.fulvum, its teleomorph Peziza ostracoderma, as well as D.abundans represent new records of fungi for South Africa. A comprehensive literature knowledge on C.fulvum and review, summarizing the existing y.fungicola is supplied, while a useful new modification of Riddell's slide culture technique is also described.