Studies on Ceratocystis spp. associated with mango die-back in Oman

Abstract

Mango wilt disease represents one of destructive diseases threatening mango cultivation in areas where it has been reported. Studies in this thesis represent the first to be undertaken after it was recognized that the disease is caused by the vascular wilt and canker pathogen Ceratocytis manginecans in Oman and Pakistan. Studies in this thesis showed clearly that the pathogen in the area represents a single clonal entity, adding credence to the view that the pathogen was introduced into Oman and Pakistan. Furthermore, the pathogen was shown to be vectored by the bark beetle Hypocryphalus mangiferae, which is native to India and has apparently been introduced into Oman, Pakistan and various other parts of the world such as Brazil where mango wilt is a serious disease. Concurrent with the appearance of mango wilt, two leguminous trees Prosopis cineraria and Dalbergia sissoo, began to wilt and die in Oman and Pakistan respectively. In this study, it was possible to show that these trees are also dying as result of infection by C. manginecans and that the pathogen appears to have undergone a host shift to these native trees. Both these tree species were shown to be susceptible to be equally susceptible to infection by C. manginecans as is mango. A final part of this investigation considered opportunities to select mango cultivars resistant to mango wilt in Oman. Here, the local mango accessions other than Pairi were shown to be highly susceptible to infection. In contrast, several mango cultivars such as Hindi Besennara, Sherokerzam, Mulgoa, Baneshan, Rose and Alumpur Baneshan had small lesions after inoculation with C. manginecans and can be considered amongst the tolerant mango cultivars. These results were also consistent with field evaluations. Studies undertaken in this thesis have added substantial information concerning mango wilt disease in Oman and it is hoped that this will help to reduce the devastation due to C. manginecans in the future.