The effect of temperature, humidity and photoperiod on the development of Neozygites cf. floridana (Weiser and Muma) in the cassava green mite, Mononychellus tanajoa (Bondar) was studied in the laboratory. Dead infected mites began to appear 2.5 days after inoculation. At 33 and 28°C peak mortalities were higher and occurred earlier (after 2.5 days), than at 23 and 18°C. Mean LT50 (time for half the infected mites to die) decreased with increasing temperature as follows: 3.9, 3.0, 2.9 and 2.5 days ...

Plantain and banana (Musa spp. AAB and AAA groups) are perennial giant herbs of the tropics which develop parthenocarpic fruits. At least three independent but complementary dominant genes control vegetative parthenocarpy in Musa. One of these genes, P1 segregates in euploid hybrid progenies derived from crosses between triploid 'French' plantains and a wild nonedible diploid banana. Linear correlation and regression analyses revealed that bunch weight and fruit weight and size were positively ...

Plantain (Musa spp., AAB group) is a major food crop in the humid lowland tropics of Africa, the Caribbean and Latin America. Lodging, caused by strong winds occurs periodically in these areas. Therefore, development of dwarf plantain cultivars and elucidation of the inheritance of dwarfism is desirable. A heterozygous normal plantain cultivar (2n= 2x) with long false‐internodes (19.4 ± 0.9 cm) was crossed with a homozygous wild banana (2n= 2x) with short false‐internodes (6.9 ± 0.4 cm) to develop ...

Bananas and plantains (Musa spp. L.) are important staple food crops in tropical countries. A major constraint to their sustainable production is black sigatoka leaf spot disease, caused by the fungus Mycosphaerella fijiensis Morelet. Resistance breeding is the most appropriate intervention to control this disease. Presence of epicuticular wax in leaves is one trait that may be involved in host plant resistance to the fungus. The inheritance of waxiness in the pseudostem, which is composed of ...

The genetics of resistance to rice yellow mottle sobemovirus (RYMV) in O. glaberrima was studied in a 6 parent full diallel cross involving 4 resistant and 2 susceptible genotypes. F1 hybrids resulting from crosses between resistant and susceptible genotypes were susceptible. Susceptibility was close to complete dominance over resistance. Estimates of genetic parameters following Hayman's and Griffing's methods indicated that additive gene effects were sigificant and more important than non-additive ...

Many isolates of cocoa swollen shoot virus (CSSV) have been found in Ghana. Relationships between these isolates have been based on symptom expression and limited serological information. This paper reports on the serological relationships between 44 accessions of CSSV using the virobacterial agglutination test. The CSSV group is differentiated into eight groups using seven antibody 'types'. The largest group comprising those isolates closely related to CSSV 1A is sub‐divided into four further ...

Stage-specific survival rates of cowpea seeds were evaluated in fields planted during both cropping seasons of 1991 and 1992 in southern Benin using Manly's regression model. Considerable seed damage could be recognised in all seed growth stages and reflected the variable pest infestations during a cropping season. An analytical approach based on the concept of competing risks and originating from human demography was used to assess the seed damage by the pod sucking bugs (PSB), Maruca testulalis ...

Success of seed development following sexual crosses is primarily dependent on proper endosperm function and development. The failure to produce triploids, or “triploid block” in 4x×2x crosses served as the impetus for numerous studies of embryo and endosperm to attempt to explain cross failure. Early explanations were based upon a concept of a 2∶3∶2 ploidy balance between maternal tissue, endosperm, and embryo. Subsequent studies done with maize demonstrated that normal endosperm development in ...

Field surveys were conducted during 1990–92 to document the relative abundance of different species of parasites of the lepidopterous stem borers Sesamia calamistis Hampson and Eldana saccharina Walker in maize fields in southwestern Nigeria. Species of parasitoids detected on both stem borers included the larval pupal parasitoids Sturmiopsis parasitica Curran (Diptera: Tachinidae) and Brachymeria feae Masi (Hymenoptera: Chalcididae), and the larval parasitoid Dolichogenidea polaszeki Walker ...

Farmers of rainfed cowpea/groundnut/millet/sorghum cropping systems in Kano, Nigeria, ranked arthropods as the major production constraint in cowpea and groundnut in 1991 and 1992. At least 25% of the farmers also reported severe infestations by Striga gesneroides a parasitic weed of cowpea. Drought was regarded as the major constraint in millet and sorghum. Farmers reported a total of 19 arthropod species, of which 10 occurred on two or more crops, five exclusively on cowpea, two on groundnut and ...