Studies of Colletotrichum gloeosporioides disease on yam, Dioscorea alata, in Solomon Islands

Abstract

A detailed account of symptoms produced by Colletotrichum gloeosporioides on susceptible and resistant cultivars of yam {Dioscorea alata) in Solomon Islands is given. A superficial blackening of upper leaf surfaces of some cultivars is unusual and worthy of further study. In pathogenicity tests with isolates of C gloeosporioides from various sources, those that were virulent on D. alata were all from D. alata except one from D. esculema and one from Cucumis sativus but only nine of 30 isolates from D. alata were virulent on this host. Since all four isolates of the yam pathogen tested on D. nummuiaria and D. trifida were virulent, it is inappropriate to retain the epiphet f. sp. alatae proposed by earlier authors. Considerable variation in cultural morphology existed among virulent isolates, the only consistent character being production of dark pigment, although this was also produced by some saprophytic isolates. Most reisolations of C. glveosporioides from lesions resulting from inoculation yielded isolates identical with the original inoculum but also some reisolates had a different morphology.

A genetic linkage map of water yam (Dioscorea alata L.) based on AFLP markers and QTL analysis for anthracnose resistance

“…QTLs specific for resistance in leaves, stems and petioles of common bean to anthracnose were also detected (Geffroy et al 2000). C. gloeosporioides attacks the vines, petioles and leaves of water yam (Winch et al 1984). Methods of assessing quantitative resistance in vines and petioles are urgently needed, in addition to the current leaf-based assays (Green et al 2000;Mignouna et al 2001a), to allow detailed genetic analysis of the components of anthracnose resistance.…”

“…Apart from recent studies on the inheritance of resistance to anthracnose disease (Mignouna et al 2001a), little is known concerning the genetics of resistance to the major pests and diseases of water yam. Anthracnose disease, caused by Colletotrichum gloeosporioides (Abang et al 2002), is a serious constraint to the sustainable cultivation of D. alata worldwide (Winch et al 1984;Nwankiti et al 1987;Macdonald et al 1998). Resistance to the moderately virulent fast-growing salmon (FGS) strain of C. gloeosporioides in the tetraploid breeding line TDa 95/00328 was found to be strain-specific and appeared to be controlled by a single major dominant locus; however, results suggested the presence of an additional resistance gene (s) (Mignouna et al 2001a).…”

Yam Propagation Using ‘Aeroponics’ Technology

“…The low rate of multiplication and the use of the edible tubers for propagation makes seed yam very expensive. Yam production therefore revolves quite repeatedly around the use of mixed genotypes, pre-infected seed yam and farmlands, causing a build-up of an array of fungal, nematode, bacterial and viral diseases and pests [2], leading to 50 to 90% yield reduction. Consequently, there is a significant demand for clean seed in a market driven seed system and 50 -70% of production costs is spent on purchase of seed yam [3,4,5].…”

Reacción de genotipos de ñame (dioscorea spp) a la antracnosis (colletotrichum gloeosporioides)

“…Esto concuerda con resultados de diferentes investigaciones que demuestran que la antracnosis es la enfermedad foliar más limitante en esta especie alrededor del mundo (Amusa 2000;Lavalett y Afanador 2007;McDonald et al 1998;Nwankiti et al 1987;Sweetmore et al 1994;Winch et al 1984). En Colombia, Campo (2000) señala que a finales de 1980 y principios de 1990, se presentó una epidemia de antracnosis que redujo más del 70% de los cultivos de ñame, debido en gran parte a la siembra en monocultivos de variedades susceptibles.…”

“…agente causal de la antracnosis. Los síntomas de esta enfermedad se manifiestan en tallo, peciolo y hoja como lesiones necróticas que dan una apariencia quemada a la zona afectada; en el tejido foliar aparecen manchas, que pueden ser de formas regulares o irregulares, de color pardo-rojizo con halos cloróticos, lo que reduce la eficiencia fotosintética de la planta y ocasiona pérdidas en la producción de más del 90% en las variedades susceptibles y disminución en la calidad de los tubérculos (Amusa et al 2003;Winch et al 1984).…”