TITLE:
First Report of Curvularia pseudobrachyspora Causing Leaf Spots Disease on Coconut (Cocos nucifera L.) Seedlings in Ghana
AUTHORS:
Emmanuellah Lekete, Enoch A. Osekre, Emmanuel Andoh-Mensah
KEYWORDS:
Leafspots, Curvularia sp., Pathogen, Phylogenetic Analysis
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.13 No.7,
July
21,
2022
ABSTRACT: Coconut (Cocos nucifera L.) is an important
oilseed and a multipurpose perennial plantation crop. It is mostly grown in
humid and coastal areas of Ghana. In June 2019, leaf spot disease was observed
on coconut seedlings in 10 coconut growing Districts in Ghana. The Initial
symptoms appeared as elliptical,
brown-dark-red lesions, 4 - 6 mm on affected leaves. Lesions reached 2.0
cm and gradually developed into spindly, dark brown spots with a light tan
centre. A study including survey and laboratory work was
carried out to assess disease prevalence and to identify the causal agent of
the disease on coconut seedlings, in order to formulate effective management
strategies against it. A total of 250 symptomatic leaves were picked from
ten selected Districts for laboratory analysis. Additionally, the ribosomal
internal transcribed spacer (ITS) region and glyceraldehyde 3-phosphate
dehydrogenase (GAPDH) of the isolated pathogen were amplified using ITS1 and
ITS4, gpd1 and gpd2 primers respectively. The
disease incidence peaked at 95%. Fungal colonies on PDA grew to 50 - 70 mm in diameter
in one week at a temperature of 28°C ± 1°C with an even to undulating, immersed
striated, mycelium; aerial mycelium being dark velvety green and sometime
woolly-cottony. Acervuli formed on the aerial mycelium and contained black powderish conidial masses. Hyphae characteristics were similar to that of Curvularia
pseudobrachyspora. Pathogenicity tests were done following
Koch’s postulate. For molecular confirmation,
the combined ITS (MT075719) and
GAPDH (MT075720) sequences were compared with published sequences of 52 Curvularia isolates and eight Bipolaris isolates using phylogenetic analysis. This is the first report of C. pseudobrachyspora as a causal agent of leaf spot on coconut seedlings in Ghana and possibly
Africa but the pathogen has been reported on other crops in China, Florida and
India.