Abstract:
Glycine max (L.) Merril (Soya bean) is one of the most important crops worldwide. It is a versatile grain legume because it has a variety of uses. A nutrient - dense food rich in protein, vegetable oil and essential minerals. The crop has the ability to fix atmospheric nitrogen and thereby improving soil fertility. Fungal mycoflora associated with the rhizosphere, rhizoplane, and non-rhizosphere of ten varieties of soya beans were isolated and studied. Dilution plate method was used in the isolation and a total of eighteen fungi were isolated at different developmental stages of the varieties. The morphological and molecular characterization of the isolates were carried out. The percentage frequencies of occurrence of the isolated organisms were determined. The organisms were screened for antagonism using dual culture technique. The interaction of variety, developmental stages and soil locations on the mycoflora were also determined. The isolated fungi were Aspergillus niger Van Tieghem, Aspergillus fumigatus Fresenius, Aspergillus flavus Link ex Grey, Aspergillus tamarii Kita , Aspergillus hortai (Langeron) Dodge, Aspergillus nidulans (Eidam) Wint, Aspergillus arcoverdensis Sigler, Rhizopus delemar Fischer, Penicillium pinophilum Link. Fries, Paecilomyces lilacinus (Thom) Samson, Blastobotrys proliferans Fulvescens (Cooke) Apinis, Talaromyces pinophilus (Hedgcock) Samson, Neosartorya fischeri (Welmer) Malloch and Cain, Botrytis cinerea Pers., Mucor micheli ex Staint-Amans, Fusarium oxysporum Link ex Fries, Helminthosporium solani Link ex Fr., and Trichoderma asperellum Persoon ex Grey. The most predominant genus in all the varieties and soil locations was Aspergillus. Fusarium oxysporum, Mucor micheli, Neosartorya fischeri and Rhizopus delemar were also strongly present in all the varieties. Aspergillus fumigatus was the least in occurrence and it occurred only on rhizosphere and non-rhizosphere soils of V2 (two unrolled trifoliate leaves) developmental stage of varieties TGM 1055 and TGM 861 respectively. Maximum frequency of occurrence of fungi was obtained from the rhizosphere soil of soya bean varieties. Fungal colonies at vegetative stages were significantly different (P<0.05) and higher than the colonies at the reproductive stages. The interactive effects of variety, developmental stages and soil locations on the colony forming unit of the mycoflora were more significant (P<0.05) at vegetative developmental stages than at reproductive stages. The interactive effect of TGM 987 with RS (Rhizosphere) and V4 (four unrolled trifoliate leaves) developmental stage gave the highest colony of 49.7±11.26 followed by TGM 861 which interacted with RS and V6 developmental stage to give a colony of 29.67±15.06 for H. solani. The potential antagonism of T. asperellum against all the isolates except R. delemar was evidenced by the results. The inhibitory effects of T. asperellum on the isolates ranged from 7.83 % to 83.88 %. T. asperellum was most virulent against B. cinerea with the maximum percentage inhibition of 83.88 % while the least inhibited was R. delemar (7.83 %). The results showed that soya bean varieties harbour diverse fungal communities which could have positive influence on the growth of the plant and the bio-control agent (T. asperellum) which can be exploited for antagonism against plant pathogenic fungi.