Sources of resistance to cassava anthracnose disease

A total of 436 African landraces and 497 improved cassava genotypes were planted in 1996, 1997, 1998 and 1999 growing seasons.. These were evaluated for their reactions to cassava anthracnose disease (CAD) under natural infection conditions at Ibadan (a high infection zone). The severity of the disease was determined by counting the total number of canker/plants and measuring the diameter the cankers. Data were collected at 6, 9 and 12 months after planting. The four-year data were pooled and subjected to statistical analysis. Result showed that of the 436 improved germplasm evaluated, 10 were resistant, 64 moderately resistant, 328 were moderately susceptible, and 95 were highly susceptible. The results also showed that 45 of the landraces were resistant, 87 moderately resistant, 354 were moderately susceptible, whereas 60 were highly susceptible. Of the resistant landraces and the improved, TME 19, TME 53, TME113, TME 244, TME 475, and TME 523; I85/02015 and I8700028 were completely free of cankers. The resistant genotypes have been introgressed into broad-based breeding populations to diversify resistance to CAD in newly improved genotypes.African Journal of Biotechnology Vol. 4 (6), pp. 570-572, 200

Biochemical and microbiological quality of honey from mangrove agro-ecological zone of Nigeria

In the present study, the biochemical and microbiological quality of honey from mangrove agro-ecological zone of Nigeria were investigated. There is paucity of information on the biochemical characteristics of honey produced from the mangrove zone of Nigeria, hence the need to provide a database on the characterization of honey produced in this zone. A total of eighteen honey samples collected from this zone were analyzed for their chemical properties including moisture, ash, pH, glucose and fructose content, while the microbial population including total plate count (TPC), total coliform and the levels of spore-forming bacteria and fungi were determined. Dat

Diallel analysis of cassava genotypes to anthracnose disease

Cassava anthracnose disease (CAD) caused by Colletotrichum gloeosporioides f. sp manihotis has been recognized as one of the major economic disease of cassava in all the cassava growing regions of Africa. Little information is available on the resistance of cassava to C. Gloeosporioides f. Sp manihotis. This study was conducted to determine the relative importance of general (GCA) and specific (SCA) combining ability, maternal and non-maternal reciprocal effects on resistance to C. Gloeosporioides f. sp manihotis in selected cassava genotypes. A complete diallel mating scheme including reciprocals of nine resistant and susceptible genotypes of cassava were evaluated in the field over a period of two planting seasons. The combining ability analysis revealed that both the additive and nonadditive gene effects were present. Crosses between the resistant lines and susceptible genotypes showed intermediate disease reaction to CAD suggesting a polygenic system of resistance to the disease. The significant maternal and specific reciprocal differences among the parents and crosses indicated that maternal and/or cytoplasmic inheritance is involved in the reaction of cassava genotypes to Colletotrichum gloeosporioides f. Sp manihotis. The significant genotype X environment interaction suggested lack of stability in the development of lesions/cankers on cassava stems. Therefore, recurrent selection would be appropriate for accumulating genes for resistance to CAD in cassavaand progeny performance may not be based on their parents performance per se

Genetic diversity of Colletotrichum gloeosporioides in Nigeria using amplified fragment length polymorphismA (AFLP) markers

Colletotrichum gloeosporioides is the causal agent of yam anthracnose disease in Nigeria. Differential cultivars and amplified fragment length polymorphic DNA markers were used to assess the extent of genetic diversity among 39 isolates of the pathogen. Fourteen (14) pathotypes of the pathogen were identified based on inoculation of a differential set of Dioscorea alata genotypes of which pathotype P11 was the most virulent attacking all differential D. alata host genotypes, while pathotype P8 was the least virulent. 52% of the isolates were avirulent, 23% were slightly virulent and 25% were virulent. Amplified fragment length polymorphism (AFLP) analysis confirmed genetic variation among the C. gloeosporioides isolates and was effective in establishing genetic relationships between them. However, the grouping of the isolates based on AFLP analysis was not directly related to virulence groups or geographical origin of the isolates. The genetic variation in C. gloeosporioides is important in choosing strategies to develop durable resistanc

Fungi associated with maize seed discolouration and abnormalities in south western Nigeria

Three seed samples of maize showing different forms of discouloration and abnormalities were screened for associated fungi. Fusarium moniliforme and Aspergillus flavus were isolated from all the categories of seed tested. The percentage incidence of F. moniliforme was significantly higher on seeds which showed white streaks, purple/pink discolouration, discoloured germ end and wrinkling than that of any other fungus. Cephalosporium acremonium and Nigrospora oryzae were also associated with purple/pink discolouration while Dreschslera maydis, Fusarium semitectum, Curvuluaria lunata and Colletotrichum graminicola were observed on seeds with brown spots. Botryodiplodia theobromae was more predominant on blackened seeds. Cephalosporium acremonium, B. theobromae, D. maydis and F. moniliforme were mainly associated with seeds with discoloured germ ends while wrinkled seeds were observed to harbour F. moniliforme, D. maydis and C. graminicola. RÉSUMÉ Trois échantillond de graines de maïs montrant differentes formes de décoloration et d'anomalies ont été évaluées pour les champignons associés. Fusarium moniliforme and Aspergillus flavus ont été isolés de toutes les catégories de graines testées. Le pourcentage d'incidence de Fusarium moniliforme était significativement plus élevé sur les graines qui ont montré des raies blanches, une décoloration purpre/rose, un bord du germe décoloré et une entorse plus que d'autres champignons. Cephalosporium acermonium et Nigrospora oryzae ont été aussi associés avec une décoloration purpre/rose alors que Dreschslera maydis, Fusarium semitectum, et Collecttrichum graminicola étaient sur les graines avec des tâches brunes. Botryodiplodia theobromae était plus dominant sur des graines noircies. Cephalosporium acremonium, B. theobromae, D.maydis et F. moniliforme étaient principalement associes avec les graines ayant des fins des germes decolores alors que les graines tordues etaient observees chez F. moniliforme, D. maydis et C. graminicola. (Af Crop Science and Production: 2001 9(4): 693-697