Abstract
Anthracnose disease is a major constraint to yam production in tropical West Africa and anywhere the crop is cultivated. This study determined the cultural characteristics and growth rates of mycelia and also characterised 6 isolates of Colletotrichum gloeosporioides, the causal agent of the yam anthracnose disease, obtained from Dioscorea rotundata leaves, vines and setts in the Tolon District of Ghana. The cultural characteristics and mycelial growth rates of the isolates were determined on Potato Dextrose Agar (PDA). The C. gloeosporioides isolates were characterised using polymerase chain reaction technique with the universal primer pairs ITS1/ITS4 and NS1/NS2, C. gloeosporioides species specific primer pairs CgInt/ITS4 and CgLac-f/CgLac-r, and C. acutatum species specific primer pairs CaGlu-f1/CaGlu-r1 and Ca-f1/Ca-r1. Based on the PCR, six isolates of C. gloeosporioides with distinct cultural characteristics were obtained. There were no significant differences (P ≤ 0.05) in mycelial growth rates among the isolates. The C. gloeosporioides isolates produced characteristic band sizes on ITS1/ITS4, NS1/NS2, CgInt/ITS4 and CgLac-f/CgLac-r. None of the isolates produced a band on CaGlu-f1/CaGlu-r1 and Ca-f1/Ca-r1. The proper identification of C. gloeosporioides, the pathogen responsible for the D. rotundata anthracnose is important for the proper management of the disease. Key words: Anthracnose disease, cultural characteristics, DNA band, morphological characteristics, Mycelial growth rate, polymerase chain reaction (PCR).
Highlights
Yam, a staple crop is mainly cultivated in the tropical and subtropical regions for its tubers (Agrios, 2005; Achar et al, 2013)
Based on the cultural and morphological characteristics, the C. gloeosporioides isolates obtained from the anthracnose infected yam leaves, vines and planting setts were grouped into six (CDr1, CDr2, CDr3, CDr4, CDr5 and CDr6) (Table 2)
The cylindrical shaped conidia with rounded ends recorded for each of the isolates CDr1, CDr2, CDr3, CDr4, CDr5 and CDr6 were similar to the observations made by Abera et al (2015) who worked on C. gloeosporioides
Summary
A staple crop is mainly cultivated in the tropical and subtropical regions for its tubers (Agrios, 2005; Achar et al, 2013) These regions provide favourable conditions that support the growth and survival of the yam anthracnose disease pathogen, Colletotrichum gloeosporioides (Penz); a major threat to yam production worldwide (Agrios, 2005; Chaube and Pundhir, 2009; Lebot, 2009; Reddy, 2015). In West African yam growing countries, the most important commercial yam species such as D. alata and D. rotundata are susceptible to the anthracnose disease (Ayodele et al, 2000; Lebot, 2009).
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