A molecular diagnostic for tropical race 4 of the banana

This study analysed genomic variation of the translation elongation factor 1 (TEF-1) and the intergenic spacer region (IGS) of the nuclear ribosomal operon of Fusarium oxysporum f. sp. cubense (Foc) isolates, from different banana production areas, representing strains within the known races, comprising 20 vegetative compatibility groups

ACIAR banana improvement project 8700 : review report

Project number related to IDRC support could not be determine

Historical overview of breeding for durable resistance to maize streak virus for tropical Africa

Maize streak virus (MSV) was first studied by Storey in Kenya in the 1920s and resistance transferred into East African maize in the 1960's. Yet the majority of farmers of East Africa are still growing streak-susceptible maize. At the International Institute of Tropical Agriculture (IITA) in Nigeria, an effort to incorporate streak resistance as an integral part of a holistic maize improvement program was begun in 1975. By 1979, usable resistance had been found and methods of large scale field challenge devised, and used routinely in the development of populations targeted at three major ecological zones in tropical Africa. Methods were continuously improved and resistant open pollinated varieties and hybrids produced that are now used on a large scale by farmers in West Africa. The strategy for success was based on: 1) Avoidance of virus strain specificity; 2) Large scale vector rearing and field infestation to ensure early infection; 3) Selection only for tolerance when infected; and 4) Not separating virus resistance selection from simultaneous selection for yield, adaptation, and resistance to other diseases important in each target ecology. The result was maize genotypes that exhibit low field incidence (tolremicity) and are tolerant (yield well even if diseased). The approach and methods have been extended to many interested national maize improvement programs and adopted by them. We believe that this form of tolerant resistance remains effective wherever deployed in Africa and thus that it has not 'broken down'

The development of hostplant resistance to insect pests: outlook for the tropics

Host-plant resistance (HPR) to insect pests is considered one of the key tactics for insect control, particularly in developing countries where utilization of other control methods such as pesticides is often difficult or unwise. The search for more sustainable methods of pest control, make host-plant resistance more attractive every day. Additionally, the opportunity for utilizing new insect resistance genes and the ability to move these across plant species, through plant biotechnology, open new doors to the field of HPR. Pest/host-plant complexes are dynamic systems influenced by numerous factors and the development of pest control strategies has to take these into consideration. Major changes in the pest complex of various tropical crops have occurred in recent years as a result of among others: the accidental introduction of new pests or the emergence of new biotypes that make previously resistant varieties ineffective, the introduction of new agronomic practices, and the deployment of new varieties with hidden susceptibility to previously minor pests. Analysis of the origin of crops and their pests is, thus, essential for devising pest control strategies and it is important to have flexible breeding programs that allow for the incorporation of new objectives as new pests come along. There is also a need to breed for varieties with durable resistance, particularly in countries where farmers cannot afford failure of HPR

Interactions among maize steak virus disease leathopper vector populations and maize cultivars in forest and savanna zones of Nigeria

Monthly plantings of three maize cultivars with differing resistance/susceptibility to maize streak geminivirus (MSV) and samplings of Cicadulina leafhopper vector were made from December 1988 to April 1990 in the humid forest and from May to November 1989 in the Guinea savanna zones of Nigeria. High MSV disease incidences (43-56%) were recorded on susceptible cultivar TZB-Gusau in late season (July-October) plantings. Hybrid 8321-21 showed significantly lower MSV disease incidence and severity than the other two cultivars, TZB-Gusau and 8329-15. Cicadulina species population peaks (5.2-13.5 leafhoppers/m2) were observed before the rains ended in savanna locations and after the end of the rains in the forest zone. Cicadulina mbila was the predominant species, whereas C.storeyi (syn. C. trangula), C. arachidis, C. similis and C. ghaurii were less common. The proportion of viruliferous leafhoppers increased as the season progressed, reaching maxima of 15-25% at the endof the growing season. Interactions between disease incidence, Cicadulina populations, maize cultivars and rainfall are discussed