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Plantain is one of the major staples contributing to food security and income generation in West and Central Africa. Local cultivars in Cameroon are susceptible to pests and diseases causing severe losses in plantain production. This study aimed at evaluating the agronomic performance and producer’s perception of plantain hybrids in the humid forest of Cameroon. Field trials were established in a completely randomized block design with eight genotypes and three replicates. Data on pest and disease as well as farmer perception were collected over two growing cycles. These genotypes included seven improved and one local genotype (check). Improved genotypes were highly tolerant to the Black Sigatoka disease compared to local plantain. While root necrosis index was above 50% in local varieties, indices below 25% were recorded in hybrids. Weevil severity in local was higher (55.0 ± 5.2%) compared to 21.0 ± 4.6% to 28.5 ± 3.2% in improved plantains. Average bunch weight was higher for FHIA 21 with 17.9 ± 0.7 kg in the first and 19.7 ± 0.3 kg for the second cycle, while those of the local Ebang were 9.6 ± 0.5 kg and 12.8 ± 0.9 kg, respectively. FHIA 21 and CRBP 568 were the preferred varieties by farmers (68.8% and 56.3% acceptance) from an agronomic perspective. The consumers’ preferences for all the genotypes varied with types of cooking. The implications of these findings for adoption by farmers and consumers as well as for the promotion of the plantain sector in central Africa are discussed.

Aphis gossypii Glover (Hemiptera: Aphididae) is among major arthropods causing significant damage to okra in the tropics. Resistant varieties could reduce aphid infestation and increase productivity. This study was carried out to identify aphid-resistant and high yielding okra accessions for management of the pest. Eleven farmers’ varieties and four aphid-resistant accessions from AVRDC were evaluated at its Nkolbisson station in Yaounde, Cameroon. Field screening was done to determine resistance to aphids, days to 50% anthesis and days to 50% commercial maturity. Aphid data was expressed as the area under infestation pressure curve and subjected to statistical analysis based on mean (m) and standard deviation (S.D.). Crop cycle and yield data were subjected to analysis of variance. Accession ‘VI033824’ was the most resistant to aphids (474 ± 41.9 per leaf) with yield 0.76 ± 0.26 t/ ha whereas the yield of the highly susceptible Babungo (1519.8 ± 0.0 aphids) was 1.33 ± 0.07 t/ha, 75.5% higher that the yield of the only resistant variety. Abelmoschus esculatus was less attacked (601.4 ± 60.0 aphids) by aphids than Abelmoschus caillei (826.0 ± 71.6 aphids; df = 1, 41; Pr {>Chi} = 0.037). The yield of A. caillei species were higher (1.26 ± 0.14 t/ha) than A. esculentus species (0.43 ± 0.08 t/ha; df = 1, 41; Pr {>Chi} = 0.0002). Hence, varieties with resistance, tolerance to aphids and earliness could be incorporated into integrated pest management of aphids and enhance productivity of okra.

The sorghum [Sorghum bicolor (L.) Moench] plant produces antimicrobial phytoalexins that are essential components of its defense mechanism against attempted infection by Colletotrichum graminicola (Ces.) G.W. Wils., the causal agent of anthracnose. Sorghum phytoaiexins are 3-deoxyanthocyanidin flavonoids shown to be luteolinidin, apigeninidin, and a caffeic acid ester of arabinosyl 5-0-apigeninidin. Crosses were made between resistant and susceptible sorghum cultivars to examine the genetic x isolate relationships of the phytoalexin response. Plants were grown in a growth chamber and in the greenhouse and inoculated with two virulent isolates and one avirulent isolate of C. graminicola 7, 21, 35, 49, and 63 d after emergence. Luteolnidin concentration was greater than that of the other phytoalexins in juvenile tissues; however, the ratios of the three compounds changed as the tissues aged and extractable amounts in tissues older than 21 d were lower than in juvenile tissues. All three phytoalexins accumulated to greater concentrations in resistant inbreds and resistant x susceptible [F.sub.1] progenies than in susceptible inbreds. These relationships were unaffected by the developmental stage of the host. Thus, analysis of phytoalexins in juvenile plants appears to be a potential tool for identification and incorporation of host resistance to C. graminicola in adult plants.

Although peri-urban vegetable production is increasingly recognized for its capacity to strengthen the resilience of the urban food system, urban expansion in most Sub-Saharan African (SSA) countries seems to pose a threat for its continuity. Thus, this article reviews the existing literature on the relationships between urbanisation and sustainability of peri-urban vegetable farms in SSA. To contribute to the understanding on how peri-urban vegetable farming can be sustained in a context of rapid urbanization in SSA, the article emphasizes the need to analyze peri-urban areas by their characteristics and argues for a conceptualization of agricultural sustainability that encompasses economic, ecological, social and land tenure dimensions. As a result, given the growing market demands, peri-urban vegetable production has ample opportunities to be sustainable and even grow; but in a context of unplanned urban expansion in poor Sub-Saharan African countries, this optimistic view should not be exaggerated. The article ends by underscoring some useful insights on policies to be taken at farm, regional, and national levels to preserve and integrate peri-urban vegetable production in the urban development process and related intervention programmes. [ABSTRACT FROM AUTHOR]

Burrowing nematodes (Radopholus similis) are among the most serious nematode pests affecting banana and plantain (Musaspp.). In Uganda, bananas, which are known locally as “matooke”, are the main staple.Radopholus similispopulations collected in four banana-growing locations (Namulonge, Mbarara, Ikulwe and Mukono) were cultured monoxenically on carrot discs, and we compared the variability in reproductive fitness and virulence (as a function of time and inoculum level) of different populations ofR. similisfrom Uganda. Their level of pathogenicity was determined by assessing the nematode reproductive ratio; that is, final population divided by the initial population. Thesein vitroexperiments showed that theR. similispopulation from Mbarara had the highest reproduction ratio, while the population from Mukono had the lowest reproduction ratio. This assessment along with pathogenicity experiments on hostMusaplants provides a means for defining pathogenicity groups amongR. similispopulations. [ABSTRACT FROM PUBLISHER]

The objective of the research was to study the genetics of host plant resistance to Radopholus similis in a diploid banana population. Screening of a hybrid population and determination of the segregation ratios can provide information on the inheritance and number of alleles controlling this trait in banana. The diploid banana hybrid population used was derived by crossing the diploid hybrids TMB2x 6142-1 and TMB2x 8075-7. The diploid banana hybrid population was evaluated with the individual root inoculation method using an R. similis population from Namulonge, Uganda. Of the 81 hybrids evaluated, 37 hybrids were resistant, 13 hybrids were partially resistant and 31 hybrids were susceptible to R. similis. After chi-square analysis, the results indicated that resistance to R. similis is controlled by two dominant genes, A and B, both with additive and interactive effects, whereby recessive bb suppresses dominant A. [ABSTRACT FROM AUTHOR]

The quantity and quality of pollen produced by a genotype are important attributes to be considered in the selection of male parents for breeding. The objective of this research was to determine the quantity and quality of pollen in 13 selected East African Highland bananas (EAHB) in relation to six diploids commonly used as male parents. Pollen quantity was scored on a scale of 0–6 while the variation of pollen stainability along the rachis was determined using acetocarmine glycerol jelly. Actual male fertility was determined by using pollen from the EAHB varieties on M. acuminata spp. burmannicoides, ‘Calcutta 4’, as the female. The diameter of 200 viable pollen grains was measured under a microscope with the aid of a graduated eyepiece. Significant differences were obtained for mean pollen stainability and pollen diameter. The pollen stainability for diploids was higher than that for the EAHB. Node numbers contributed significantly to variation of pollen stainability in EAHB ( P ≤ 0.01) and ‘Pisang lilin’ ( P ≤ 0.001). ‘Pisang lilin’ and the EAHB varieties had about 100 nodes as opposed to about 200 in other diploids. The EAHB varieties produced less pollen than most of the diploids. The actual male fertility of EAHB varieties was low (1 seed/bunch), compared to that of ‘Calcutta 4’ (223.3 seeds/bunch) and ‘Pisang lilin’ (13.7 seeds/bunch). Although the production of 2 n pollen in EAHB varieties was low (0–7%), the potential exists for using them in new breeding approaches. [ABSTRACT FROM AUTHOR]

The burrowing nematode, Radopholus similis, is a serious threat to sustainable banana production worldwide. A promising way of controlling nematodes is through the development and deployment of resistant cultivars. This usually involves crossing triploid cultivars with fertile diploids to produce tetraploids that generally display greater male and female fertility. Selected tetraploids are then crossed with improved diploids to produce sterile secondary triploids. This study evaluates the host response of the most commonly grown East African highland bananas in Uganda. Also, the host responses of diploid hybrids and East African highland banana derived hybrids, including tetraploids and secondary triploids, were evaluated. The individual root inoculation method was used for screening the Musa accessions for resistance to R. similis. The final nematode population of each accession was compared with the final nematode population of a susceptible reference cultivar, Valery, and with the final nematode population of a resistant reference cultivar, Yangambi km5. Results show that, except for cv. Muvubo, East African highland bananas were as susceptible to R. similis as cv. Valery. Four out of 13 tetraploid hybrids were identified with resistance to R. similis, as well as 13 out of 19 diploids and five out of 18 secondary triploids. [ABSTRACT FROM AUTHOR]

The effects of nematode infection and mulching on plantain cv. Agbagba (Musa spp., AAB-group, false horn) yield and plantation longevity were examined in a field experiment at the High Rainfall Station of the International Institute of Tropical Agriculture (IITA) at Onne in southeastern Nigeria. The 2nd, 3rd and 4th crop cycles (1st, 2nd and 3rd ratoon, respectively) following the plant crop cycle (mother crop) were examined in nematode inoculated or non-inoculated and mulched or non-mulched treatments. Nematodes (Radopholus similis, Helicotylenchus multicinctus and, to a lesser extent, Helicotylenchus dihystera, Hoplolaimus pararobustus and Meloidogyne spp.) were inoculated at planting of the mother plant, but were also present in relatively high population densities in the non-inoculated treatments at harvest of the 1st crop cycle. Plants inoculated with nematodes failed to reach harvest and neither did plants in the non-inoculated non-mulched treatments in any ratoon. Only non-inoculated mulched plants reached harvest, producing 0.85, 1.22 and 0.2 Mg ha-1, respectively in the 1st, 2nd and 3rd ratoon, taking toppled, broken and dead plants into consideration. Mulched plants were larger, had more suckers, survived longer and had healthier root systems compared with non-mulched plants. Damage to roots was greater in the inoculated plants compared with the non-inoculated plants for the 1st and 2nd ratoons but not for the 3rd ratoon. Radopholus similis was most strongly associated with root damage (percentage root necrosis and dead roots), although H. multicinctus population densities were also positively correlated with percentage root necrosis. At flowering of the 1st ratoon, 71% of the inoculated non-mulched plants were dead compared with only 1% of the non-inoculated mulched plants. Helicotylenchus multicinctus remained the most abundant nematode throughout the experiment. Together with R. similis, it comprised over 95% of the plant-parasitic nematode population. [ABSTRACT FROM AUTHOR]