pically. They were found to form colonies with white
mycelia, becoming green when forming conidia and conidiophores.
There were conidia formed densely over the center and undulating
concentric rings toward the edge. According to Kubicek and
Harman (2002), they were identified as Trichoderma spp. Also,
growth of the pathogenic isolates on PDA produced aerial (dense
and floccose) whitish mycelia. Observation through the bottom
of Petri dishes showed production of yellowish/cream-white pigmentations by some isolates at young age. These colours either
remained with time or changed into purple or whitish. The growth
rate of almost all isolates ranged between 2.5 and 5.0 cm after
4 days. On CLA, all the isolates showed slightly sickle-shaped
macroconidia, with foot-shaped basal cells and 3–5 septates moderately curved 27 5.0 lm. Microconidia produced on long monophialids were abundant, oval-shaped and mostly two-celled. These
characteristics designated the fungus to be Fusarium sp. (Leslie and
Summerell, 2006)). The pathogenicity of Fusarium isolate is presented at pot experiment section below.
Preliminary studies identified the Fusarium isolate FS1 as having
the highest disease severity and aggressiveness (data not shown)
on the bean plants, and was therefore progressed and used for all
subsequent studies.
3.1.2. Molecular characterization of fungal isolates and phylogenic
analysis based on rDNA sequencing data
The most potent Trichoderma isolate and the most pathogenic
Fusarium isolate were selected for molecular identification and taxonomy analysis. All fungal isolates were identified using ITS
regions of rDNA and BLAST search. The isolates of Trichoderma
sp. and Fusarium sp. showed 100% homology with T. atroviridae
AY380906 and 99% homology with Fusarium solani FJ345352
respectively. They were therefore named as Trichoderma atroviridae
and Fusarium solani f. sp. Phaseoli respectively (Fig. 1).
The phylogenetic analysis was based on the data from T. atroviridae and F. solani respectively, together with those that presented similarity in the NCBI database, and other sequences
belonging to different families and orders, with the objective of
confirming that the isolates are grouped with the families and
the closest BLAST identity. The phylogenetic analysis is presented
in Fig. 1.