Preliminary studies of isozyme patterns of isolates of colletotrichum gloeosporioides from host plants in Malaysia

Isozyme variation of 25 isolates of Colletotrichum gloeosporioides from 12 different Malaysian host plants were studied using polycrylamide gel electrophoresis. The hosts included seven species of legumes and one species Fach of citrus, grass, cocoa, pepper and chiUi. One to five electromorphs per enzyme were produced for the five enzyme systems typed. Some isolates did not produce any bands for the enzymes studied. Double to multiple bands were observed with esterases, MDH, GLDH and LDH. Only one pepper isolate produced a single band for GDH. Some variations among the isolates of different host plants were observed with the isozyme patterns of esterases and MDH. Isozyme tests may prove to be a useful tool in the identification of C. gloeosporioides of different host plants when mOre samples are tested in future

Comparative studies of isolates of colletotrichum gloeosporioides from eighteen Malaysian hosts

Colletotrichum gloeosporioidesfrom eighteen Malaysian hosts, namely mandarin orange (Citrus reticulata), cacao (Theobroma cacao), an orchid (Cattleya sp.), pepper (Piper nigrum), chilli (Capsicum annum), grass (Imperata cylindrica), mango (Mangifera indica) and legume cover crops (Pueraria phaeseoloides, Centrosema pubescens, and Calopogonium mucunoides) and a weed (Mimosa pudica), vegetables (Psophocarpus tetragonolobus, Phaseolus vulgaris, Vigna radiata, Vigna sesquipedalis and Arachis hypogaea), a shrub (Leucaena leucocephala) and a herbaceous vine (Clitoria ternatea) were examined for colony growth characteristics, morphology of conidia, growth on various media and temperatures and pathogenicity on Phaeseolus bean hypocotyls. Conidium size ofColletotrichum gloeosporioides was 14.25-19.0 x 2.7-5.03 llm. The appressorium size was 6.34-10.08 x 5.28-7.31 llm and the shape was globose/sub-globose/lobed. No correlation between the appressorium size and shape was noticed. The optimum temperature for growth was 28 and 30°C. None of the isolates caused infection symptoms on Phaseolus bean hypocotyls

Seed mycofloras of hyacinth beans (Lablab niger) and long beans (Vigna sesquipedalis) and their pathogenic importance

Isolations and identifications of seed-borne fungi from two seed lots of Lablab niger and Vigna sesquipedalis seed were made. Among the various species of fungi isolated, Curvularia sp., Drechslera sativum, Diplodia sp., Chaetomium globosum, Pestalotiopsis sydowiana, Aspergillus spp. and Fusarium spp. were the most common on these two beans. Nigrospora sacchari and Phyllosticta sp. were confined to L. niger. Macrophomina phaseolina and Colletotrichum sp. were found only on V. sesquipedalis. Selected fungi were isolated, and tested for pathogenicity to emerging seedlings and established seedlings of L. niger and V. sesquipedalis. Phyllosticta sp., Diplodia sp., Drechslera sativum and Macrophomina phaseolina were found to be pathogenic. The pathological importance of these fungi is further discussed

Studies on the potential of biological control of the anthracnose fungi Colletotrichum in Malaysian fruits.

Anthracnose or Gloeosporium fruit rot is one of the most severe diseases in the fruit production. The causal fungus, Colletotricum species attacks fruits, flowers, stems and leaves of crops such as Avocado, Mango, beans, banana, papaya and Guava. In the pursuit of extending the shelf life of Malaysian fruits for export purposes, biological control was tried using three species of Trichoderma. In vitro studies in the laboratory show that the antagonistic species has potential as biocontrol agents as they reduce radial growth of cultures, spore germination of 6 species of Colletotricum. These fungi alfo reduced disease symptoms of anthracnose in infected banana fruits. Antagonistic action between the fungal hyphae are also observed by the use of light microscopy

Seed borne fungi of Brassica chinensis L. and Brassica rapa L. and their pathogenic importance

In using the filter paper and agar plate procedures, a total of 35 species of fungi, namely, Alternaria brassicae, Aspergillus aculeatus, Acflavus, A. ochraceous, A. terreus, Botryodiplodia theobromae . Choanephora curcurbitarum, Circinella, sp., Cladosporium sphaerosporum, Colletotrichum sp., Cylindocladium sp., Curvularia lunata. C. pallescens, C. oryzae, Diaporthe sp., Erysiphe sp., Fusarium equiseti, F. fusaroides, F. oxysparum, F. moniliforme var subglutinans, Helminthosporium sp., Macrophomina phaseolina, Nigrospora orvzae, Paccilornyces sp., Penicillium nigricans, P. nototum, P. rugulosum, P. wortmanii, Peronospora sp., Pest alotia sp., Phaetricoconis sp .. Phomu linguni. Pythium sp .. Rhizopus stolonifer and Syncephalastruni racemosum were found to be present on seeds of Brassica chinensis and B. rapa. Both Malt extract agar and Potato Dextrose agar gave more infection counts of seeds than filter paper. Surface disinfection with mercuric chloride eliminated contaminants like Aspergillus spp., Penicillium sp., and some mucuraceous fungi, but did not affect germination. Inclusion of sodium chloride in media, allowed growth of osmophilic fungi and did reduce germination of seeds. Soil inoculation tests on emerging seedlings using nine selected isolates indicated, that all fungal isolates tested were pathogenic to seeds and seedlings of Brassica spp. with Brassica chinensis being more susceptible than B. rapa. Macrophomina phaseolina is reported as a pathogen of Brassica spp. for the first time

Approach to biological control of anthracnose fruit rot of bananas.

Biological control using associated members of the banana fruit microflora for controlling anthracnose disease caused by Colletotrichum musae, in ripening and ripe bananas was investigated. Among twenty nine fungi and three bacteria isolated from the surface of the fruit, those found non-pathogenic to banana fruit, were tested for antagonistic activity using opposed colony technique. Aspergillus paradoxus, Trichoderma pseudokoningii, Trichoderma aureoviride and three separate isolates of Penicillium species showed varying degrees of antagonistic activity against C. musae. So these were selected for further invitro studies.Culture filtrates of these fungi significantly reduced radial growth of C. musae on Potato Dextrose Agar and inhibited spore germination and germ tube elongation of C. musae. The filtrates however enhanced appressoria formation.Appressoria were formed as soon as a germ tube protrude from the conidia. Further the culture filtrates of one of the Penicillium species and T. aureoviride reduced significantly the production and spread of lesions on the fruits. The results of the study indicated the possible use of antagonistic species of fungi for biocontrol of anthracnose fruit rot of bananas

Further trials with seed dressings for the control of leaf stripe Pyrenophora avenae in Northern Ireland oats

Significantly better control of leaf stripe of oats caused '9Y mercury tolerant Pyrenophora avenae was obtained by the use of a proprietary fungicide containing organomercury + carboxin than by the use of one containing only organomercury but there was not a significant difference between organomercury + carboxin and carboxin alone. Three other experimental materials gave results not significantly different from. those for organomercury but they were phytotoxic