African Crop Science Journal <p>The <em>African Crop Science Journal,</em> a quarterly publication, publishes original research papers dealing with all aspects of crop agronomy, production, genetics and breeding, germplasm, crop protection, post harvest systems and utilisation, agro-forestry, crop-animal interactions, information science, environmental science and soil science. It also publishes authoritative reviews on crop science and environmental issues by invitation. It is bilingual, publishing in either English or French. </p><p>Other websites related to the journal include: <a title="" href="" target="_blank"></a></p> African Crop Science Society (Uganda) en-US African Crop Science Journal 1021-9730 Copyright for articles published in this journal is retained by the journal. Karyotypic analyses of accessions of Kersting’s groundnut <p>Kersting’s groundnut (Macrotyloma geocarpa) is an orphan crop of significant food and household income in sub-Saharan Africa. The objective of this study was to evaluate the chromosomal variability among the accessions of the species through analysis of the karyotypes. Six accessions of Kersting’s groundnut were subjected to conventional cytological techniques, using root tip meristems. The somatic chromosome number was 2n = 20 in all the accessions. The highest total chromosome length was obtained in Tkg 1 (1.739 + 0.047); while the least was in Tkg 12 (1.014 + 0.029). All the accessions had metacentric, submetacentric and subtelocentric chromosomes. However, there was a preponderance towards metacentric chromosomes, suggesting a symmetrical karyotype, which is known to be a primitive condition. Five of the accessions were grouped in karyotype 2A while one accession, Tkg 9 was grouped in karyotype 2B. The 2B karyotypes are known to have greater chromosomal asymmetry than 2A; thus Tkg 9 may be advancing evolutionarily faster than the other accessions. Hierarchical cluster analysis divided the accessions into three clusters. Cluster 1 comprised of four accessions (Tkg 1, Tkg 6, Tkg 9 and Tkg 11); while Cluster 2 comprised of one accession (Tkg 6); and cluster 3 had one accession (Tkg 12). Tkg 6 and Tkg 12 were observed to be distantly related to the other accessions; as such could serve as parents in hybridisation programmes to generate wider variability for the improvement of the species.</p> I.C. Odo F.I. Akaneme Copyright (c) 29 2 177 191 10.4314/acsj.v29i2.1 Management of Lasiodiplodia theobromae, the causal agent of mango tree decline disease in Ghana <p>Mango (Mangifera indica L.), is one of the economically most important crops in Ghana. It is recognised for its popularity in contributing to food and nutritional security. Despite its economic importance, mango tree decline disease, caused by Lasiodiplodia theobromae, poses a serious threat to the mango industry in the country. The objective of this study was to evaluate fungicides (i.e., carbendazim, zamir, mancozeb, funguran and sulphur 80) and bio pesticides (Chromolaena odorata, Azadirachta indica and Carica papaya) against L. theobromae. The results showed that all the tested fungicides, except for sulphur 80, inhibited mycelial radial growth of L. theobromae, with carbendazim and funguran improving the vegetative growth of the shoots and leaves in the field. Mango trees treated with carbendazim, after the third spray, had no disease symptoms. However, application of urea fertiliser and carbendazim (50 g 15 L-1 water), at a two-week spraying interval in the field, reduced the severity of L. theobromae. Application of biopesticides (plant extracts) showed that C. odorata had the highest efficacy, followed by A. indica and then C. papaya. Although further studies on plant extracts in the field are required, our findings provide important information for the development of integrated management strategies for the pathogen, and the disease it transmits.</p> F.K. Ablormeti S.R. Coleman J.O. Honger E. Owusu I. Bedu O.F. Aidoo E.W. Cornelius G.T. Odamtten Copyright (c) 29 2 193 207 10.4314/acsj.v29i2.2 New sources and stability of resistance to aphids in cowpea germplasm across locations in Uganda <p>The cowpea aphid (Aphis craccivora Koch) is an economically important pest, whose feeding effects cause stunting, delayed flower initiation and yield reduction in cowpea (Vigna unguiculata L. Walp). Host plant resistance offers an alternative for controlling aphids; while simultaneously reducing reliance on chemical pesticides. The objective of this study was to evaluate a multi-parent advanced generation inter-cross (MAGIC) population of cowpea against aphids, across cowpea growing regions in Uganda. The study was arranged in alpha lattice design, with two replicates in three locations over two seasons (2018B and 2019A). Results revealed significant effects (P&lt;0.001) for the main treatment effects, genotype x location and location x season interaction for both infestation and damage. The genotype x season interaction was significant (P&lt;0.01) for both aphid infestation and damage; while the three-way interaction was only significant (P&lt;0.001) for aphid infestation, but not for damage. The study identified five new resistant and stable genotypes from the MAGIC panel, including MAGIC131, MAGIC-132, MAGIC149, MAGIC170 and MAGIC280; and one resistant parent, SUVITA-2. The study further revealed MAGIC-125, MAGIC-171, MAGIC153, MAGIC-333, MAGIC177, MAGIC-292, MAGIC282, MAGIC249, MAGIC162, SEC 4W * SEC 5T, NAROCOWPEA 4, MAGIC-204, MAGIC-039, MAGIC060, MAGIC-097, NAROCOWPEA 3, MAGIC-233, MAGIC090 and MU 9 to be moderately resistant and high yielding genotypes. The above genotypes are recommended for use in the cowpea breeding programme, to develop improved resistant lines against aphids in Uganda.</p> R. Kityo J.B. Odoi A. Ozimati I.O. Dramadri R. Agaba P.O. Ongom P. Nampala R. Edema R. Edema J. Karungi P. Gibson P.R. Rubaihayo Copyright (c) 29 2 209 228 10.4314/acsj.v29i2.3 Farmers’ preference for onion varieties and implications of knowledge of Iris yellow spot disease in Kenya <p>Thrip transmitted Iris yellow spot disease (IYSD) is an economically important viral disease, affecting bulb onions worldwide. Recommended IYSD resistant varieties are not commonly grown in countries like Kenya, yet inappropriate disease control measures are applied upon disease occurrence in the fields. This is presumably due to lack of knowledge on the disease and/or recommended varieties do not match farmers’ preferred traits. The objective of this study was to assess farmers’ knowledge of IYSD and their criteria for selecting onion varieties for/against IYSD in Kenya. A study was conducted with 360 respondents across three onion growing agro-ecological zones (AEZ) in Kenya, during 2019-2020. Farmers’ fields were assessed for IYSD incidence and severity. All farmers acknowledged the existence of IYSD based on diseased plants in the field. However, majority of the farmers (95.6%) were not aware of the cause of the disease. Onion thrips and IYSD susceptible red onion varieties were the most preferred (77.9%) by farmers. Preference for these varieties was based on their high yielding capacity, early maturity, strong pungency, marketability and long shelf life. Most farmers (59.8%) relied on fungicides to control IYSD, though ineffectively. Lack of appropriate management strategies for IYSD was due to lack of knowledge on the disease diagnosis, epidemiology as well as cultivation of IYSD susceptible red varieties.</p> R.K. Birithia S. Subramanian D.K. Kuria Copyright (c) 29 2 229 239 10.4314/acsj.v29i2.4 Evaluation of tomato genotypes for tolerance to major diseases in Uganda <p>Tomato (<em>Solanum lycopersicum</em> L.) is a priority vegetable in Uganda, but due to its limited genetic base, its cultivated types are prone to a variety of diseases. The objective of this study was to evaluate new tomato genotypes for resistance to major tomato diseases under hotspot conditions in Uganda. Fourty-five tomato genotypes were evaluated for reactions to tomato bacterial wilt, tomato bacterial speck, early blight and late blight. The study was conducted for two rainy seasons in 2019, at the National Crops Resources Research Institute, Namulonge in Uganda. Data for severity and incidence were collected at two-week intervals after transplanting. Twelve genotypes (Nouvella F1, Rambo F1, Commando F1, AVTO1315, AVTO922, AVTO1701, AVTO1219, AVTO1464, MT56, ADV1287A, Pruna and Vega) exhibited high levels of tolerance to bacterial wilt; while bacterial speck presented mild symptoms majorly seen on Vega, Zodiac and AVTO9802. Rhino, AVTO1418, AVTO1314, Eureka, Roma VFN, MT56, Pinktop, Assila F1, Money-maker, AVTO0922 and AVTO1464 were the least affected by early blight; while AVTO1219, AVTO1701, ADV12021, ADV12076 and ADV1287A expressed low AUDPC values for late blight. Overall, AVTO1315 was the best yielder (30.8 metric tonnes ha-1), followed by AVTO0301 (29.0 t ha-1) and Nouvella F1 (26.1 t ha-1). Among the tomato genotypes evaluated, we recommend AVTO1701, AVTO0922, AVTO1464, AVTO0301 AVTO1315, AVTO1219, Pruna, Vega, ADV1287A and MT56 for the national performance trials.</p> I. Ramathani G. Ddamulira A. Kangire P. Wasswa A. Tusiime Copyright (c) 29 2 241 258 10.4314/acsj.v29i2.5 Leveraging early dry season planting of ginger under irrigation to enhance production from bacterial wilt infected seed rhizome <p>Ginger (<em>Zingiber officinale</em> Rosc.), one of the important export crops grown in Ethiopia for its underground aromatic rhizome, is threatened by the destructive Ginger Bacterial Wilt (GBW) disease. The objective of this study was to evaluate the effect of moisture sources, plant spacing, and nitrogen fertiliser, on rhizome yield and yield attributes of latently infected ginger seed rhizomes. Treatments included two levels of moisture sources (irrigation and rainfall), two levels of plant spacing (40 cm x 15 cm and 40 cm x 30 cm), and three rates of nitrogen fertiliser, i.e., 0, 46 and 92 kg N ha 1 applied in the form of urea. Analysis of variance showed significant (P&lt;0.01) variations between moisture sources and planting space for fresh rhizome yield, but not for N levels. Moisture sources also significantly (P&lt;0.01) affected stand count at harvest, and other yield attributes, viz., number of buds per rhizome per hill, number of rhizomes per plant, rhizome size and rhizome and propagule weight. Planting infected ginger rhizomes early in dry season, with irrigation, led to production of healthy and large rhizomes weighing up to 662 g. Narrow plant spacing showed better yield performance and yield attributes, as opposed to wide spacing; though wide plant spacing was more preferred for management of Ginger Bacterial Wilt during humid and warm weather conditions. This experiment clearly demonstrated that planting ginger rhizomes, which are latently infected with <em>Ralistonia solanacearum</em> early in dry season, using irrigation could be the best option to propagate disease free rhizomes since dry condition successfully restrains bacterial development, disintegrating the pathosystem. i.e., avoiding high humidity, which is one of the ideal conditions for bacterial growth. Early planting in dry season, using irrigation is a cost effective and easily applicable practice to control Ginger Bacterial Wilt disease.</p> Asfaw Kifle Derbew Belew Copyright (c) 29 2 259 275 10.4314/acsj.v29i2.6 Host-plant and insect-pest compensations, and microclimate as drivers for intensity of Toxoptera aurantii (Hemiptera: Aphididae) in Arabica coffee-banana farming system of mount Elgon region, Uganda <p>Host-plants and insect-pests’ compensational relationships are known to enable plants and insects to survive and adopt to changing environmental conditions. In the mount Elgon region of Uganda, exists a mosaical pattern of different coffee farming systems with increasing altitudes, and their combinations create differing microclimates, which influence host-plant and pest behaviors. The objective of this study was to determine the host-plant and <em>Toxoptera aurantii</em> compensations in Arabica coffee cropping systems of mount Elgon region in Uganda. A two-year study on the coffee leaf biomass, <em>T. aurantii</em> numbers on the leaf surface, and damage intensity of <em>T. aurantii</em>, was conducted using 72 Arabica coffee farms with mixed coffee polycultures (farming systems). Two independent factors were considered; altitude as a major factor and the farming system as the second factor. There was evidence of significant host-plant and insect-pest compensations; host-plant/microclimates, and insect-pest /microclimates. Linear regression analysis revealed a - relationship (number of leaves /branch / <em>T. aurantii</em> numbers). A + relationship (number of leaves / branch infested by<em> T. aurantii / T. aurantii</em> abundance). Also<em> T. aurantii</em> abundance had a + relationship / RH or/ambient temperature). The Arabica coffee leaves/ branch had a – relationship (ambient temperature or/ RH). While the <em>T. aurantii</em> infested leaves /branch only had a + relationship with RH. Regarding the soil variables it was only soil temperature which had a + relationship with the number of leaves /branch. The <em>T. aurantii</em> infested leaves /branch had a + relationship (soil temperature or/soil moisture).</p> A.R. Ijala S. Kyamanywa C. Cherukut C. Sebatta T. Hilger J. Karungi Copyright (c) 29 2 277 292 10.4314/acsj.v29i2.7 Genetic variability and character association for bulb yield and yield related traits in garlic in Ethiopia <p>Garlic (<em>Allium sativum</em>) has for centuries been valued by humans for food, culinary and medicinal purposes world over. The objective of this study was to investigate genetic variability among garlic accessions for yield, yield related and phenology traits in Ethiopia. A field study was conducted at the DebreZeit Agricultural Research Center during 2012, using 49 garlic accessions from the highlands of North Shewa, East and West Arsi, Arsi, Bale and Sidama zones, which are among the major garlic producing areas in Ethiopia. The experiment was arranged in a 7x7 simple Lattice design, with two replications. Accession were highly significant (P &lt; 0.01) for days to maturity, leaf number per plant, neck diameter, yield per plant, biological yield per plant, dry weight above ground, bulb dry weight, dry weight underground, clove number per bulb, and clove weight per bulb. Heritability estimates ranged from 82.48% for clove number, to 6.46% harvest index. High heritability, combined with high genetic advance (as per cent of mean) observed for mean clove number, yield per plant, biological yield per plant and clove weight per plant showed that these characters were controlled by additive gene effects. Thus phenotypic selection for these characters would likely be effective in variety selection and development. Bulb yield per plant had positive and highly significant genotypic and phenotypic correlations, with all characters, except plant height and harvest index. Path analysis at phenotypic level revealed that biological yield and bulb dry weight contributed major positive direct effects to bulb yield per plant. These traits showed positive and highly significant genotypic correlations with bulb yield except harvest index</p> A. Tesfaye D.F. Mijena H. Zeleke G. Tabor Copyright (c) 29 2 293 308 10.4314/acsj.v29i2.8 Stay green physiological capacity of drought tolerant maize inbred lines <p>Stay green is the ability of a plant to maintain photosynthetically functional green leaf area for longer periods, even under excessive water stress. This study was done to establish the physiological capacity of Ugandan drought tolerant maize inbred lines to stay green under water shortage conditions using various stay green physiological determinants. Seventy-six maize inbred lines characterised for drought tolerance by CIMMYT, were planted under a rain out shelter, with a well-watered control (WW) and excessive water-stress treatments applied at six weeks after planting (6 WAP) and eight weeks after planting (8 WAP). The most maintained stay green physiological determinants under excessive water-stress were non-photosynthetic quench (NPQt) and leaf pigmentation per unit leaf area (RC: LAUG) with inbred lines CELQ15028 and CELQ15022 showing the highest maintenance for the two parameters, respectively. The highest level of variation for quantum yield of photosystem II activity (Phi2) and NPQt among inbred lines was at 40 and 60 days after flowering, respectively. Phi2 was negatively correlated to NPQt but positively correlated to the linear electron flow (LEF); while NPQt had a significantly negative correlation with LEF. This study established that these drought tolerant maize inbred lines have moderate stay green physiological capacity, with inbred line CEL15027 performing the best.</p> G.T. Epaku P. Rubaihayo F. Kagoda K.D. Bomet A. Badji I. Chapu G. Ogwal Copyright (c) 29 2 309 323 10.4314/acsj.v29i2.9