Plant-Parasitic Nematodes and Food Security in Sub-Saharan Africa

Sub-Saharan Africa (SSA) is a region beset with challenges, not least its ability to feed itself. Low agricultural productivity, exploding populations, and escalating urbanization have led to declining per capita food availability. In order to reverse this trend, crop production systems must intensify, which brings with it an elevated threat from pests and diseases, including plant-parasitic nematodes. A holistic systems approach to pest management recognizes disciplinary integration. However, a critical under-representation of nematology expertise is a pivotal shortcoming, especially given the magnitude of the threat nematodes pose under more intensified systems. With more volatile climates, efficient use of water by healthy root systems is especially crucial. Within SSA, smallholder farming systems dominate the agricultural landscape, where a limited understanding of nematode problems prevails. This review provides a synopsis of current nematode challenges facing SSA and presents the opportunities to overcome current shortcomings, including a means to increase nematology capacity

Occurence of plant parasitic nematodes and factors that enhance population build-up in cereal-based cropping systems in Uganda

Plant parasitic nematodes remain a major challenge to crop production that has hitherto received minmum research attention in sub-Saharan Africa. This paper gives the diversity of nematode genera and species associated with cereal crops and indicates the possibility of nemadode population build up due to production intensification especially in soils with high sand content. Twenty-two nematode species from 10 genera of plant parasitic nematodes were recovered in root samples collected from 5 cereal crops (barley, maize, millet, sorghum and wheat) collected from 293 sites in five major cereal growing areas of Uganda (230 maize samples, 18 millet samples, 21 sorghum samples, 18 wheat samples and 6 barley samples), grown singly or as intercrops. Of these, 12 nematode species were encountered in maize roots, namely Aphelenchoides arachides, Aphelenchoides eltaybi, Ditylenchus spp, Helicotylenchus dihystera, Meloidogyne spp., Pratylenchus brachyurus, Pratylenchus goodeyi, Pratylenchus zeae, Scutellonema brachyurus, Scutellonema paralabiatum, Scutellonema clathricaudatum andRotylenchulus borealis. Based on populations of the nematode species recovered, four distinct nematode groupings were observed: those that were widespread and abundant (Pratylenchus zeae and P. brachyurus); those that were widespread but less abundant (Scutellonema spp., Meloidogyne spp., Rotylenchulus spp. and Helicotylenchusspp.); those that were localized but very abundant (Pratylenchus goodeyi), and those that were localized but less abundant (Aphelenchoides spp. and Ditylenchus spp.). Intensified maize cropping systems with/without noncereal rotations increased risk of Pratylenchus zeae, Scutellonema spp. and Helicotylenchus spp. infection of maize

Abundance and diversity of arthropod pests infesting stored maize in smallholder farmers and traders systems highlight critical points for pest management in Uganda: Presentation

Knowledge of the diversity of arthropod pests infesting stored maize value chain in Uganda is very scanty to guide the development and implementation of management strategies. From a cross-sectional study conducted in north western, eastern and central regions of Uganda during 2017/2018, the diversity and economic importance of storage arthropod pests of maize in farmer storage, trader/retailer stores in villages and townships, and in milling and processing facilities is presented. A total of 11 insect pests were recorded feeding internally and externally on stored maize. Rhyzopertha dominica, Sitophilus zeamais and Sitophilus oryzae were the primary insect pests followed by Tribolium spp., Cryptolestes spp., Sitotroga cerealella, and Oryzaephilus mercator. The highest insect diversity and damage was recorded when maize was stored with husked cobs in farmers’ houses, a practice farmers use to store seed for next planting. Meanwhile the distribution pattern of the pests in trader/retailer stores in villages and townships, and in milling facilities indicate waves of insect infestation occurring with stocks of grain being brought in storage. The maize grain at the peak of harvesting was in excellent quality but later stocks brought in several months after harvest were infested with diverse insects. Re-drying at farm level and use of chemical dusts at trader/retailer stores in villages and townships were the most common pest management practice. However, the lack of a differentiated market, whereby better quality would fetch premium price, discourages investment to reduce postharvest losses. Subsequently, most farmers sold their grains immediately after harvest and most traders sold their stocks as soon as there was the next bulk buyer. The critical point for pest management is at farm level where pest diversity and damage is greatest, and at the village/ township stores where the grain may be held in anticipation of improvement in price.Knowledge of the diversity of arthropod pests infesting stored maize value chain in Uganda is very scanty to guide the development and implementation of management strategies. From a cross-sectional study conducted in north western, eastern and central regions of Uganda during 2017/2018, the diversity and economic importance of storage arthropod pests of maize in farmer storage, trader/retailer stores in villages and townships, and in milling and processing facilities is presented. A total of 11 insect pests were recorded feeding internally and externally on stored maize. Rhyzopertha dominica, Sitophilus zeamais and Sitophilus oryzae were the primary insect pests followed by Tribolium spp., Cryptolestes spp., Sitotroga cerealella, and Oryzaephilus mercator. The highest insect diversity and damage was recorded when maize was stored with husked cobs in farmers’ houses, a practice farmers use to store seed for next planting. Meanwhile the distribution pattern of the pests in trader/retailer stores in villages and townships, and in milling facilities indicate waves of insect infestation occurring with stocks of grain being brought in storage. The maize grain at the peak of harvesting was in excellent quality but later stocks brought in several months after harvest were infested with diverse insects. Re-drying at farm level and use of chemical dusts at trader/retailer stores in villages and townships were the most common pest management practice. However, the lack of a differentiated market, whereby better quality would fetch premium price, discourages investment to reduce postharvest losses. Subsequently, most farmers sold their grains immediately after harvest and most traders sold their stocks as soon as there was the next bulk buyer. The critical point for pest management is at farm level where pest diversity and damage is greatest, and at the village/ township stores where the grain may be held in anticipation of improvement in price

Socioeconomic constraints to sustainable cocoyam production in the Lake Victoria Crescent

Cocoyam production has the potential of significantly improving the food security status and income levels of farmers in the Lake Victoria region. The study covered various areas of the three East African states, Kenya, Uganda and Tanzania as follows: Kisumu, Kakamega and Siaya districts in Kenya; Bukoba in Tanzania; and Mukono, Wakiso and Kampala in Uganda. Structured questionnaires were used to collect data from a total of 283 respondents. Results showed that farmers had an adequate level of education that enabled them utilize cocoyam production technologies. However, land scarcity was the major factor limiting cocoyam cultivation. This was attributed to the fact that cocoyam cultivation was restricted to wetlands, which was already a limited resource in the region. Other factors such as diseases, weeds, pests, scarcity of labour, unavailability of extension services and planting material and improved varieties, among others influenced the production of the crop. Research and development agencies in the study area need to develop appropriate cocoyam production technologies to mitigate existing constraintsKey words: Cocoyam production, social and economic constraints, Lake Victoria region

MORPHOLOGICAL AND AGRONOMIC TRAITS VARIATIONS FOR MUNGBEAN VARIETY SELECTION AND IMPROVEMENT IN UGANDA

Mungbean ( Vigna radiata L. Wilczek), is a pulse species that is widely cultivated in sub-tropical and tropical regions of the world. Unfortunately, the yield of mungbean in Uganda is very low mainly due to inherent genotype failures and losses due to pests and diseases. To achieve a gain in yield through breeding requires collection, characterisation, and evaluation of germplasm, as the first step in identifying genotypes with the desired characteristics. The objective of this study was to describe the nature and extent of genotypic variation among mungbean collections for a range of traits of potential agronomic and adaptive interests in Uganda. A total of 35 mungbean accessions acquired mainly from the World Vegetable Centre (AVRDC) in Taiwan, two local ricebean ( Vigna umbellata (Thunb.) Ohwi and Ohashi) and one local blackgram genotype ( Vigna mungo ) were evaluated for several diverse traits for two cropping seasons at two different locations in Uganda. Genotype by environment interaction (GEI) was significant (P < 0.001) for all the traits, indicating inconsistent performance by some genotypes across two locations and two seasons. However, AMMI bi-plot identified stable genotypes for grain yield, while GGE bi-plot identified the best genotypes in a hypothetical environment. The magnitudes of estimated broad sense heritability (H) for the traits used were generally high. However, single link dendogram and Principal Component Analysis (PCA) revealed narrow diversity in the mungbean collection. The positive relationship between seed size and yield in this sub-set of mungbean germplasm can be used in a breeding programme for a potential gain in selecting large seeded and high yielding genotypes.Le haricot mungo ( Vigna radiata L. Wilczek), est une esp\ue8ce de plante qui est largement cultiv\ue9e en r\ue9gions tropicales et subtropicales. Le rendement actuel du haricot mungo en Ouganda est comparativement bas par suite d\u2019\ue9checs li\ue9s au g\ue9notype et pertes dues aux maladies et pestes. Afin de r\ue9aliser un gain de rendement \ue0 travers l\u2019am\ue9lioration, il s\u2019av\ue8re n\ue9cessaire de faire la collection, la caract\ue9risation, et l\u2019\ue9valuation du germplasme, comme premi\ue8re \ue9tape dans l\u2019identification des g\ue9notypes avec des caract\ue9ristiques d\ue9sir\ue9es. La variation parmi 38 accessions de haricot mungo obtenues du World V\ue9g\ue9tale Centre (AVRDC), une vari\ue9t\ue9 locale de haricot riz ( Vigna umbellata (Thunb.) Ohwi et d\u2019 Ohashi) et un g\ue9notype de blackgram ( Vigna mungo ) local, \ue9tait \ue9valu\ue9e pour plusieurs traits directs pendant deux saisons culturales dans des lieux diff\ue9rents en Ouganda. Une variation substantielle \ue9tait observ\ue9e dans diff\ue9rent traits de potentiel agronomique et performance adaptive. L\u2019interaction g\ue9notype par environnement (GEI) \ue9tait significatif (P < 0.001) pour tous les traits, indiquant une performance inconsistante de quelques g\ue9notypes \ue0 travers deux milieux et deux saisons. Par ailleurs, un AMMI bi-plot a identifi\ue9 des g\ue9notypes stables en termes de rendement en grain, alors que le GGE bi-plot a identifi\ue9 les meilleurs g\ue9notypes dans un environnement hypoth\ue9tique. Les niveaux de l\u2019h\ue9ritabilit\ue9 estim\ue9e (H) pour les traits utilisees \ue9taient g\ue9n\ue9ralement \ue9lev\ue9s. Par ailleurs, le lien simple du dendogramme et l\u2019analyse par composantes Principales (PCA) ont r\ue9v\ue9l\ue9 une petite diversit\ue9 dans la collection du haricot mungo. Une corr\ue9lation positive entre la taille du grain et le rendement dans ce sous groupe du germoplasme du haricot mungo peut \ueatre utilis\ue9e dans le programme d\u2019am\ue9lioration pour un gain potentiel dans la s\ue9lection des g\ue9notypes \ue0 grains larges et rendement \ue9lev\ue9s

Agricultural Nematology in East and Southern Africa : Problems, Management Strategies and Stakeholder Linkages

This is the peer reviewed version of the following article: Herbert Talwana, et al, ‘Agricultural nematology in East and Southern Africa: problems, management strategies and stakeholder linkages’, Pest Management Science Vol. 72 (2): 226-245, February 2016, which has been published in final form at http://dx.doi.org/10.1002/ps.4104. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. © 2015 Society of Chemical Industry.By 2050, Africa’s population is projected to exceed two billion. Africa will have to increase food production more than 50% in the coming 50 years to meet the nutritional requirements of its growing population. Nowhere is the need to increase agricultural productivity more pertinent than in much of sub-Saharan Africa where it is currently static or declining. Optimal pest management will be essential, because intensification of any system creates heightened selection pressures for pests. Plant-parasitic nematodes and their damage potential are intertwined with intensified systems and can be an indicator of unsustainable practices. As soil pests, nematodes are commonly overlooked or misdiagnosed, particularly where appropriate expertise and knowledge transfer systems are meager or inadequately funded. Nematode damage to roots results in less efficient root systems that are less able to access nutrients and water, which can produce symptoms typical of water or nutrient deficiency, leading to misdiagnosis of the underlying cause. Damage in subsistence agriculture is exacerbated by growing crops on degraded soils and in areas of low water retention where strong root growth is vital. This review focuses on the current knowledge of economically important nematode pests affecting key crops, nematode control methods, and the research and development needs for sustainable management, stakeholder involvement and capacity building in the context of crop security in East and Southern Africa, especially Kenya, Tanzania, Uganda and Zimbabwe.Peer reviewe

Evaluation of the American yam bean (Pachyrhizus spp.) for storage root yield across varying eco-geographic conditions in Uganda

Open Access Article; Published online: 15 June 2019The American yam bean (Pachyrhizus spp.) is a legume crop that is exclusively used for its storage roots. The seeds are inedible due to presence of toxic rotenone. It produces high storage root yields comparable of major root crops like cassava or sweetpotato. And flower pruning more than doubles its root yield performance. Using twenty five yam bean accessions, the current study aimed to determine root yield stability and adaptability, and presence of yam bean production mega environments in Uganda. Trials were planted at three stations, Namulonge, Serere, and Kachwekano during two consecutive seasons of 2011. Fresh storage root yields were significantly different (p < 0.05) across locations with the ideal location being Namulonge (fresh storage root yield of 10.1 t ha-1), followed by Serere (8.0 t ha-1), and Kachwekano (3.1 t ha-1). Results of AMMI analysis indicated the presence of genotype-by-environment interaction for fresh storage root yield. Through AMMI estimates and GGE visual assessment, genotype 209017 was the highest yielding with mean yield of 20.7 t ha-1. Genotype 209018 with mean yield of 15.5 t ha-1 was the most stable and adapted accession in the entire discriminating environment in Uganda. From the environmental focusing plot, the six environments were grouped into two putative mega environments for yam bean production

Response of banana hybrids to the banana weevil (Cosmopolites sordidus Germar) (Coleoptera: Curculionidae) in Uganda

Banana weevil (Cosmopolites sordidus (Germar) is one of the major constraints to banana production in Uganda. A field screening experimentwas undertaken at Kawanda to determine the response of 18 hybrids to the banana weevil (Cosmopolites sordidus (Germar).Based on total cross-sectional damage, results indicated that there was improved resistance to banana weevil in the hybrids tested. Damage scores for all the tested hybrids were significantly different from the susceptible check (Atwalira). Except M4, M5, M6 and M8, the rest of the hybrids showed significant difference from the resistant cultivar (Yangambi KM 5). Data on mat disappearance showed that hybrids were more stable than the susceptible check, while findings from weevil trap catches suggested no relationship between attraction and weevil damage. Resultsshowed that some hybrids have superior agronomic and yield characteristics, however due to high weevil infestation, the findings of the study were not representative of maximum yield potential that may be achieved under good management practices

Effect of marker aided pyramiding of anthracnose and pythium root rot resistance genes on plant agronomic characters among advanced common bean genotypes

This is an open access article that can be downloaded directly from the publsher's site at http://www.ccsenet.org/journal/index.php/jas/article/view/35870One of the factors that accounts for the low yields in common bean is the simultaneous occurrence of diseases on the common bean crop. Bean root rots and anthracnose are the most important common bean diseases that simultaneously occur on the bean crop in Uganda. Moreover, Colletotrichum lindemuthianum, the pathogen that causes bean anthracnose, possesses a high genetic variability which makes it easily break down single gene resistance. Pyramiding resistance genes for both diseases in commercial varieties would ensure reduction of yield losses resulting from the two diseases. However, the effect of marker assisted gene pyramiding on plant agronomic characters is not well understood. Three-way crosses were made to pyramid three anthracnose and one Pythium root rot resistance genes in four susceptible market class varieties. Sequence characterized amplified regions (SCAR) markers were used to facilitate the pyramiding scheme. Correlation analysis and Path coefficient analysis were used to assess the association between number of pyramided genes and different plant agronomic characters. Number of pyramided genes was negatively correlated with number of pods per plant (-0.32), number of seeds per plant (-0.25), number of seeds per pod (-0.18), pod length (-0.17), days to 50% flowering (-0.09) and 100-seed weight (-0.02). Path coefficient analysis showed that number of pyramided genes, plant height, days to 50% flowering, number of seeds per pod and number of pods per plant had negative direct effects on seed weight per plant. Number of seeds per plant had the highest positive direct effects (0.98) followed by 100-seed weight (0.28) while days to maturity had the least positive direct effect (0.03) on seed weight per plant. Only number of seeds per plant had its correlation coefficient (0.94) almost equal to the direct path coefficient (0.97). Number of pyramided genes had significant (P < 0.05) negative indirect effect on seed weight per plant only through number of seeds per plant (-0.25). Therefore, pyramiding higher numbers of resistance genes may cause a grain yield reduction via number of seeds per plant. Therefore, it is important for breeders to simultaneously select for number of pyramided genes with number of seeds per plant and other highly associated traits.Uganda National Council for Science and Technology (MSI project). International Center for Agriculture in the Tropics (CIAT/PABRA-Uganda), and The National Agricultural Research Organization (ATAAS project)

RESISTANCE OF NAPIER GRASS CLONES TO NAPIER GRASS STUNT DISEASE

Napier grass ( Pennisetum purpureum Schumach) is the major livestock fodder under intensive and semi-intensive systems in East Africa. However, the productivity of the grass is constrained by Napier grass Stunt Disease (NSD). The purpose of this study was to identify Napier grass clones with resistance to NSD. Seven introduced Napier grass, from the International Livestock Research Institute (ILRI) gene bank in Ethiopia, and 3 locally available clones in Uganda, were screened for resistance to NSD. Napier grass Stunt Disease severely infected plants tended to have more tillers (r = 0.84, P&lt;0.001), but reduced biomass (r = -0.70, P&lt;0.001) and height (r = -0.88, P&lt;0.001). The reaction of the clones ranged from highly susceptible (clones 16795 and 16792), moderately susceptible (P99, KW4, 16806, 16803, 16785, local and 16814) to resistant (16837). Clone P99 was moderately susceptible to NSD but its harvestable biomass was least affected by disease infection, thus could be, in the interim, utilised in integrated NSD management as the search for more resistant clones is expedited.Le Napier ( Pennisetum purpureum Schumach) est un fourrage important pour l\u2019\ue9levage dans les syst\ue8mes intensifs et semi-intensifs en Afrique de l\u2019est. Par ailleurs, la productivit\ue9 de cet aliment fait face au probl\ue8me de productivit\ue9 de cette herbe qui est affect\ue9 par la maladie du rabougrissement de Napier (NSD). L\u2019objet de cette \ue9tude \ue9tait d\u2019identifier les clones du Napier introduit et localement disponible avec r\ue9sistance au NSD. Sept Napiers introduits en provenance du la banque de g\ue8ne de l\u2019Institut International de Recherche sur l\u2019Elevage (ILRI) en Ethiopie, et trois clones locaux disponibles en Ouganda \ue9taient \ue9valu\ue9s pour leur r\ue9sistance \ue0 cette maladie dans un essai au champ au \u2018National Crops Resources Research Institute (NaCRRI)\u2019 \ue0 Namulonge en Ouganda. La r\ue9action de ces clones variait de hautement susceptible (16795 et 16792), mod\ue9r\ue9ment susceptible (P99, KW4, 16806, 16803, 16785 et 16814) \ue0 r\ue9sistant (16837 et local). La maladie de rabougrissement des plants s\ue9v\ue8rement infect\ue9e tendaient d\u2019avoir significativement plus de talles (r = 0.84, P&lt;0.001) mais avec de la biomasse (r = -0.70, P&lt;0.001) et hauteur (r = -0.88, P&lt;0.001) r\ue9duites. Les clones P99 et 16837 mod\ue9r\ue9ment susceptibles au NSD mais dont leur biomasse n\u2019\ue9tait pas affect\ue9 par by l\u2019infection de la maladie, pourrait \ueatre, dans l\u2019int\ue9rim, utilis\ue9s dans la gestion int\ue9gr\ue9e du NSD pendant que la recherche des clones plus r\ue9sistants continue