EFFECT OF THE CULTURE FILTRATE OF TWO SOIL FUNGI ASPERGILLUS FLAVUS

EFFECT OF THE CULTURE FILTRATE OF TWO SOIL FUNGI ASPERGILLUS FLAVUS LINK. AND ASPERGILLUS NIGER VAN TIEGHAM ON GERMINATION AND RADICLE DEVELOPMENT OF COWPEA (VIGNA UNGUICULATA WALP.) AND TOMATO (LYCOPERSICON ESCULENTUM MILL.) A DISSERTATION PRESENTED BY PATRICK QUARCOO NYAMATA IN PART FULFILMENT OF THE REQUIREMENTS FOR THE B.SC (HONOURS) DEGREE IN BOTANY OF THE UNIVERSITY OF GHANA THE DEPARTMENT OF BOTANY UNIVERSITY OF GHANA LEGON JUNE, 2000. ABSTRACT The effect of metabolites of Aspergillus flavus and Aspergillus niger on germination and development of cowpea (Vigna unguiculata Walp. Vars. Asontem Red and IITA -1977) and Tomato (Lycopersicon esculentum Mill. Var. Wosowoso) have been investigated using the Blotter Test Method. The effect of the metabolites on seedling development under greenhouse conditions were also studied in pots containing soil moistened with the culture filtrate of A.niger and A.flavus. Percentage germination and radicle development of the cowpea varieties were inhibited by the metabolites of the Aspergillus species. There were varietal differences in the effect of metabolites of A.niger and A.flavus on the same crop. Metabolites of A.niger and A.flavus did not significantly (P=0.05) inhibit germination of tomato seeds but adversely depressed its radical development. The metabolites of A.niger were more repressive in their effect on plant development. The inhibitory effect of the metabolites of the Aspergillus species were gradually removed with increasing dilution of the culture filtrates up to 1:10 v/v dilution. Undiluted filtrate and filtrate dilutions of 1:1 vlv of A.niger metabolites prevented the radicles from forming lateral roots, and which subsequently died. Samples moistened with filtrates of higher dilutions (1:5 vlv, 1:10 v/v) developed lateral roots and survived. Germination of Cowpea (Var. Asontem Red) placed in undiluted filtrate and filtrate dilution 1:1 vlv of A.niger was depressed by 47.4 -84.2% whereas cowpea var. IITA -1977 given the same treatment was depressed by 66.7 -94.4%. Culture filtrate of A.niger significantly (Student's t-test P≥0.05) depressed plant height and leaf length of cowpea while there was no significant difference between the control and A.flavus-treated seedlings. No significant differences were observed in the leaf width between the control and A.flavus -treated and A.niger -treated plants even after 28 days. The weight of shoot and root of A.niger – treated plants were adversely affected. The weight of shoot and roots were significantly lower than that of control seedling treated with distilled water. A.flavus – treated plants produced root and shoots whose total weight nearly approximated that of the control seedlings. Practical implications of the results are discussed and future studies suggested.