Biological control of fungi associates in soursop (Annona muricata) leaf spot disease by using Trichoderma harzianum / Nurul Syafika Muslimin

Soursop (Annona muricata) is known for its ethnomedicinal uses, leading to the increasing demand for the fruits. In Malaysia, leaf spot disease is one of the major constraints in the soursop plantation. If unattended, the possibility for the disease to cause huge economic losses in the soursop industry are highly possible. Thus, this study aimed to determine the morphological characteristic of the isolated fungi associated with leaf spot disease of soursop, to assess molecular identification of the isolated fungi by amplification of ITS regions, to analyse the antagonistic activity of Trichoderma harzianum against identified fungal isolates by using an application of dual culture test in vitro, to determine the severity of infection of identified pathogenic fungi on the soursop saplings in vivo, and to determine the capability of T. harzianum as plant growth-promoting fungi (PGPF) on soursop saplings in vivo. The leaves and soil samples from the infected soursop trees with leaf spot disease symptoms were collected from the farms located in Seri Menanti, Negeri Sembilan and Bukit Kurau, Perak, Malaysia. Cultivation was done on Potato Dextrose Agar (PDA) medium. The morphology of the fungal isolates was identified using fungal slide culture method Then, further identification for the fungal species was done molecularly by amplification of ITS region. Antagonistic activity of T. harzianum against fungal isolates was identified using dual culture method and its capability as plant growth - promoting fungus was done by application of T. harzianum suspension on soursop saplings. From the results, twenty-six morphologically distinct fungi isolates were identified and only 12 fungal isolates were suspected to be pathogenic.