Optimisation of in vitro techniques for cassava brown streak virus elimination from infected cassava clones

Cassava brown streak disease (CBSD), caused by Cassava brown streak virus (CBSV), is an economically important disease of cassava (Manihot esculenta Crantz) in East Africa. The objective of this study was tooptimise in vitro techniques for CBSV elimination from infected Ugandan cassava cultivars. Using semi-solid halfstrength Murashige and Skoog (MS) basal medium, hormone concentration and heat treatment regimes wereoptimised for micropropagation of farmer’s preferred cassava cultivars and CBSV elimination. Single nodes from young cassava stems were cultured for four weeks on ½MS medium supplemented with 6-benzyl amino purine(BAP) and 2,4-dichlorophenoxy acetic acid (2,4-D). The BAP and 2,4-D concentration (mg l-1) combinations used were 0.0 and 0.0, 0.5 and 0.1, 1.0 and 0.2, 1.5 and 0.3, and 2.0 and 0.4, respectively. The optimum medium was used for in vitro thermotherapy using four temperature regimes, namely 30-34, 34-38, 36-40 and 38-42 oC for 8 hoursdarkness and 16 hours light, respectively, for four weeks. The best plantlet growth in terms of height was observed on MS medium supplemented with 0.5 mg l-1 BAP and 0.1 mg l-1 2,4-D. Highest CBSV elimination efficiency of 40%, with 49% plantlet survival was observed at 36 oC for 8 hours darkness and 40 oC for 16 hours light. These results indicate that in vitro techniques can greatly enhance CBSV elimination and, thus, provide a means of CBSD management through dissemination and conservation of popular but CBSD susceptible cultivars

Optimisation of in vitro techniques for Cassava brown streak virus elimination from infected cassava clones

Cassava brown streak disease (CBSD), caused by Cassava brown streak virus (CBSV), is an economically important disease of cassava ( Manihot esculenta Crantz) in East Africa. The objective of this study was to optimise in vitro techniques for CBSV elimination from infected Ugandan cassava cultivars. Using semi-solid half-strength Murashige and Skoog (MS) basal medium, hormone concentration and heat treatment regimes were optimised for micropropagation of farmer's preferred cassava cultivars and CBSV elimination. Single nodes from young cassava stems were cultured for four weeks on 1/2MS medium supplemented with 6-benzyl amino purine (BAP) and 2,4-dichlorophenoxy acetic acid (2,4-D). The BAP and 2,4-D concentration (mg 1-1) combinations used were 0.0 and 0.0, 0.5 and 0.1, 1.0 and 0.2, 1.5 and 0.3, and 2.0 and 0.4, respectively. The optimum medium was used for in vitro thermotherapy using four temperature regimes, namely 30-34, 34-38, 36-40 and 38-42 \ub0C for 8 hours darkness and 16 hours light, respectively, for four weeks. The best plantlet growth in terms of height was observed on MS medium supplemented with 0.5 mg 1-1 BAP and 0.1 mg 1-1 2,4-D. Highest CBSV elimination efficiency of 40%, with 49% plantlet survival was observed at 36 \ub1C for 8 hours darkness and 40 oC for 16 hours light. These results indicate that in vitro techniques can greatly enhance CBSV elimination and, thus, provide a means of CBSD management through dissemination and conservation of popular but CBSD susceptible cultivars.La maladie de la striure brune du manioc (CBSD) caus\ue9e par le virus de la striure brune (CBSV), est une maladie \ue9conomiquement importante du manioc ( Manihot esculenta Crantz) en Afrique de l'Est. L'objectif de cette \ue9tude \ue9tait d'optimiser les techniques in vitro pour l'\ue9limination du CBSV des cultivars ougandais infect\ue9s. En utilisant le m\ue9dium basal semi-solid half strength Murashige and Skoog, la concentration d'hormone et les regimes de traitement de chaleur \ue9taient optimis\ue9s pour la micropropagation des cultivars de manioc pr\ue9f\ue9r\ue9s par les fermiers et l'\ue9limination du CBSV. Les nodes simples des jeunes tiges de manioc \ue9taient cultiv\ue9s pendant quatre semaines sur le m\ue9dium 1/2 MS suppl\ue9ment\ue9s avec 6-benzyl amino purine (BAP) et 2,4-dichlorophenoxy acetic acid. Les combinaisons de concentrations (mg 1-1) de BAP et de 2.4-D utilis\ue9es \ue9taient 0.0 et 0.0, 0.5 et 0.1, 1.0 et 0.2, 1.5 et 0.3, et 2.0 et 0.4, respectivement. Le m\ue9dium optimum \ue9tait utilis\ue9 pour la thermoth\ue9rapie utilisant quatre regimes de temp\ue9rature dont 30-34, 34-38, 36-40 et 38-42 \ub0C pendant 8 heures en obscurit\ue9 et 16 heures sous lumi\ue8re, respectivement pendant quatre semaines. La meilleure croissance en hauteur des plantules \ue9tait observ\ue9e sur le m\ue9dium MS suppl\ue9ment\ue9 avec 0.5 mg 1-1 BAP et 0.1 mg 1-1 2,4-D. L'efficience la plus \ue9lev\ue9e de 40 % en terme d'\ue9limination du CBSV, avec 49 % de la survie de plantules \ue9tait observ\ue9e \ue0 36 \ub0C pendant 8 heures sous obscurit\ue9 et 40 \ub0C pendant 16 heures sous lumi\ue8re. Les r\ue9sultats indiquent que les techniques in vitro peuvent grandement promouvoir l'\ue9limination du CBSV et offrent ainsi un moyen de gestion de CBSD \ue0 travers la dissemination et la conservation des cultivars aussi populaires que susceptibles au SBSD

Risk factors for non-communicable diseases in rural Uganda: a pilot surveillance project among diabetes patients at a referral hospital clinic

Introduction: Despite an increasing recognition of non- communicable diseases (NCDs) in sub-Saharan Africa, there is lack of well established surveillance systems for these diseases. In an effort to understand burden of NCDs in low-resource settings, the African Field Epidemiology Network launched a pilot project in 2009 to routinely capture patient data in the diabetes clinic of Mbarara Regional Referral Hospital. The objective of this study was to determine the prevalence and, the gender- and age- specific distributions of common NCD risk factors among diabetic patients attending a referral hospital in rural Uganda. Methods: A relational Access database was designed to collect information on NCD risk factors. These included smoking, alcohol use, family history of diabetes, hypertension and body mass index. Univariate analyses were done and differences in proportions tested using chi-square P-values in STATA version 10.0. Results: A total of 1,383 patient records were analyzed, with 61% being female and mean age of 39.6 years (SD 15.8). About 24% had a family history of diabetes. Smoking and alcohol use were more prevalent among males (16.6 % vs. 8.3%; p<0.0001) and (30.7 vs. 13%; p<0.0001) respectively. Overweight, obesity and hypertension were more prevalent in women (18.6% vs. 9.7%, 8.6% vs. 2.6%; p<0.0001, and 40.3% vs. 33%, p=0.018) respectively. Conclusion: This pilot project shows that use of hospital-based data is a valuable initial step in setting up surveillance systems for NCDs in Uganda. Risk factors for NCDs were both age and gender-specific and predominantly related to lifestyle. This suggests the need to design gender-sensitive prevention interventions that target lifestyle modification in this setting

Performance and inheritance of yield and maize streak virus disease resistance in white maize and yellow conversions

In sub Saharan Africa, past effort has registered success in developing high yielding and foliar disease resistant maize ( Zea mays L.) varieties, which are deficient in pro-vitamin A. A new initiative is to develop maize varieties, tolerant to foliar diseases and rich in pro-vitamin A carotenoids. To achieve this, yellow conversions of white testers and other elite maize varieties have been developed by the International Center for Maize and Wheat Development (CIMMYT). Unlike the white lines, limited information on agronomic performance and disease resistance is available for yellow maize conversions. This study was conducted to evaluate the performance of white maize and their corresponding yellow maize conversions for yield and tolerance to Maize streak virus (MSV) disease; and determine the inheritance patterns of these traits. Fourty seven three-way hybrids generated in a Line by tester mating design (North Carolina 2), 12 inbred lines (used as male parents), 4 single crosses (used as female parents) and 3 commercials checks were screened for resistance to Maize streak virus (MSV) disease at the National Crop Resources Research Institute (NaCRRI) in Uganda. The same genotypes were evaluated in a 9x5 alpha lattice design in three locations of Uganda (National Crop Resources Research Institute (NACRRI), National Semi Arid Resources Research Institute (NaSARRI) and Bulambuli) for agronomic performance. Results confirmed tolerance to MSV in testers CML202, CML395, CML444, CML445 and CML312-SR (white). Genotypes performed significantly differently for yield, anthesis days, plant height, ear height, husk cover, grain texture, reaction to Gray leaf spot (GLS) (P<0.001) and ear aspect (P<0.01). However, pairwise comparison of white and yellow conversions indicated no significant difference (P>0.05) in agronomic performance and tolerance to diseases. General combining ability (GCA) was more important than specific combining ability (SCA) for most traits, except for anthesis days, Turcicum leaf blight (TLB), GLS and yield. GCA effects for yield were not significant in both lines (male parents) and single cross testers (female parents) of white and yellow conversions. However, two unique cases were observed for diseases; yellow conversion of line CML444 significantly combined for susceptibility to TLB; while tester CML312/CML442 combined for resistance to GLS. Additionally, there was low heritably estimates for tolerance to MSV and yield. Generally, there was no significant difference between white and corresponding yellow maize conversion, implying that there is no significant loss in MSV resistance and yield performance while converting white into yellow maize.En Afrique sub-Saharienne, les efforts ant\ue9rieurs ont connu de grands succ\ue8s dans le d\ue9veloppement des vari\ue9t\ue9s tr\ue8s productives et tol\ue9rantes aux maladies foliaires du ma\uefs ( Zea mays L.), mais qui sont pauvres en provitamine A. La nouvelle vision est de d\ue9velopper des vari\ue9t\ue9s de ma\uefs r\ue9sistantes aux principales maladies foliaires, et riche en carot\ue9no\uefdes provitamine A. Pour y arriver, les conversions jaunes issues des testeurs blancs de ma\uefs ainsi que les vari\ue9t\ue9s \ue9lite ont \ue9t\ue9 d\ue9velopp\ue9es par le Centre International pour l\u2019Am\ue9lioration du Ma\uefs et du Bl\ue9 (CIMMYT). Contrairement aux lign\ue9es blanches de ma\uefs, la performance agronomique et le niveau de r\ue9sistance aux maladies des lign\ue9es jaunes reste m\ue9connue. Cette \ue9tude a \ue9t\ue9 men\ue9e dans le but d\u2019\ue9valuer la performance au niveau du rendement et la r\ue9sistance \ue0 la maladie des bandes (MSV) des vari\ue9t\ue9s de ma\uefs \ue0 grain de couleur blanche et leurs conversions de couleur jaune et d\ue9terminer le mode d\u2019h\ue9ritabilit\ue9 de ces deux param\ue8tres \ue9tudi\ue9s. Quarante-sept hybrides trois voies produits dans un mode de croisement Lign\ue9e par testeur (North Carolina II), 12 lign\ue9es \ue9pur\ue9es (utilis\ue9es comme parents m\ue2les), 4 hybrides simples (utilis\ue9s comme parents femelles) et 3 t\ue9moins ont \ue9t\ue9 inocul\ue9s par l\u2019agent causal de la maladie des bandes \ue0 NaCRRI (National Crop Ressources Research Institute) en Ouganda. La performance agronomique des m\ueames g\ue9notypes a \ue9t\ue9 \ue9valu\ue9e dans un dispositif exp\ue9rimental d\u2019alpha lattice (5parcelles \ue9l\ue9mentaires x 9 blocks) dans 3 sites de l\u2019Ouganda \ue0 savoir NaCRRI (National Crop Ressources Research Institute), NaSARRI (National Semi Arid Resources Research Institute) et Bulambuli. Les r\ue9sultats ont confirm\ue9 la tol\ue9rance \ue0 la MSV des testeurs \ue0 grains blancs CML202, CML395, CML444, CML445 et CML 312-SR. La performance des g\ue9notypes \ue9tait hautement significativement diff\ue9rente pour le rendement, le nombre de jours de floraison m\ue2le, la hauteur des plants, le niveau d\u2019insertion des \ue9pis sur les plants, la couverture des \ue9pis par les spathes, la texture des grains, la r\ue9action \ue0 la GLS (Glay leaf spot) (P<0.001) ainsi que pour l\u2019aspect des \ue9pis (P<0.01). Cependant, la comparaison entre le ma\uefs blanc et sa conversion jaune a montr\ue9 une diff\ue9rence non significative (P>0.05) au niveau de leur performance agronomique et la tol\ue9rance aux maladies. L\u2019aptitude g\ue9n\ue9rale \ue0 la combinaison (GCA) \ue9tait plus importante que l\u2019aptitude sp\ue9cifique \ue0 la combinaison (SCA) pour la plupart des param\ue8tres \ue0 l\u2019exception du nombre de jours \ue0 floraison m\ue2le, la tol\ue9rance \ue0 l\u2019helminthosporiose (TLB), GLS et le rendement. Les effets dus \ue0 la GCA pour le rendement n\u2019\ue9taient pas significatifs pour les parents m\ue2les (lign\ue9es) et femelles (hybrides simples) des g\ue9notypes \ue0 grain de couleur blanche et leurs conversions \ue0 grain de couleur jaune. N\ue9anmoins, deux cas exceptionnels ont \ue9t\ue9 observ\ue9s pour la tol\ue9rance aux maladies: la conversion jaune de la lign\ue9e CML444 \ue9tait un mauvais combinateur pour la TLB, alors que le testeur CML312/CML442 combinait bien pour la tol\ue9rance \ue0 la GLS. En plus, l\u2019h\ue9ritabilit\ue9 \ue9tait faible pour la tol\ue9rance \ue0 la MSV et le rendement. En g\ue9n\ue9ral, il n\u2019y avait pas de diff\ue9rence significative entre les g\ue9notypes \ue0 grain blanc et leurs conversions jaunes respectives, ce qui signifie que, lors de la conversion des vari\ue9t\ue9s \ue0 grain blanc en vari\ue9t\ue9s \ue0 grain jaune, il n\u2019y a aucune perte significative en ce qui est de la tol\ue9rance \ue0 la MSV et la performance en rendement des grains

Evaluation of tomato genotypes for tolerance to major diseases in Uganda

Tomato ( Solanum lycopersicum 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.La tomate ( Solanum lycopersicum L.) est un l\ue9gume prioritaire en Ouganda, mais en raison de sa base g\ue9n\ue9tique limit\ue9e, ses types cultiv\ue9s sont sujets \ue0 une vari\ue9t\ue9 de maladies. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer des g\ue9notypes de tomates s\ue9lectionn\ue9s pour leur r\ue9sistance aux principales maladies de la tomate dans des conditions de hotspot en Ouganda. Quarante-cinq g\ue9notypes de tomates ont \ue9t\ue9 \ue9valu\ue9s pour leurs r\ue9actions au fl\ue9trissement bact\ue9rien de la tomate, \ue0 la tache bact\ue9rienne de la tomate, au mildiou et au mildiou. L\u2019\ue9tude a \ue9t\ue9 men\ue9e pendant deux saisons des pluies en 2019, au National Crops Resources Research Institute, \ue0 Namulonge en Ouganda. Les donn\ue9es de gravit\ue9 et d\u2019incidence ont \ue9t\ue9 recueillies \ue0 des intervalles de deux semaines apr\ue8s la transplantation. Douze g\ue9notypes (Nouvella F1, Rambo F1, Commando F1, AVTO1315, AVTO922, AVTO1701, AVTO1219, AVTO1464, MT56, ADV1287A, Pruna et Vega) pr\ue9sentaient des niveaux \ue9lev\ue9s de tol\ue9rance au fl\ue9trissement bact\ue9rien; tandis que la tache bact\ue9rienne pr\ue9sentait des sympt\uf4mes b\ue9nins principalement observ\ue9s sur Vega, Zodiac et AVTO9802. Rhino, AVTO1418, AVTO1314, Eureka, Roma VFN, MT56, Pinktop, Assila F1, Money-maker, AVTO0922 et AVTO1464 ont \ue9t\ue9 les moins touch\ue9s par le mildiou; tandis que AVTO1219, AVTO1701, ADV12021, ADV12076 et ADV1287A ont exprim\ue9 de faibles valeurs AUDPC pour le mildiou. Dans l\u2019ensemble, AVTO1315 a \ue9t\ue9 le meilleur producteur (30,8 tonnes m\ue9triques ha-1), suivi par AVTO0301 (29,0 t ha-1) et Nouvella F1 (26,1 t ha-1). Parmi les g\ue9notypes de tomates \ue9valu\ue9s, nous recommandons AVTO1701, AVTO0922, AVTO1464, AVTO0301 AVTO1315, AVTO1219, Pruna, Vega, ADV1287A et MT56 pour les essais de performance nationaux

Portable PCR field-based detection of sweetpotato viruses

Sweetpotato ( Ipomoea batatas Lam.) production is greatly constrained by viral infections, especially Sweet potato feathery mottle virus and Sweet potato chlorotic stunt virus that synergistically cause a severe sweetpotato virus disease. The impact of viruses is aggravated by the vegetative nature of the crop and inaccessibility to dependable diagnostic tools in rural areas where sweetpotato production is done. This makes it hard for seed inspectors to perform quality checks prior to use of vines for planting. The objective of this study was to develop a procedure that allows for detection of sweetpotato viruses on-site. This involved modification of the Lodhi et al. (1994) nucleic acid extraction procedure, by omitting some of the laboratory specific steps and varying the incubation time in liquid nitrogen, instead of the freezer. Incubation in liquid nitrogen for only 1.5 hours yielded as high quality RNA compared to that of the original protocol, when incubation was done at 4\ub0C overnight in a freezer. Reverse transcriptase (RT) was run using a portable miniPCR thermocycler; and the resulting cDNA was amplified using this miniPCR machine instead of using a laboratory stationed conventional PCR thermocycler. The cDNA was efficiently amplified and amplicons were similar to those obtained with the original extraction protocol and subsequent amplification by the conventional RT-PCR. Our protocol reduced extraction time from about 16 hours for the original protocol, to about 2 hours and 45 minutes. If this tool is utilised by the crop protection departments, we believe it will contribute greatly towards sustainable sweetpotato production through making timely recommendations.La production de la patate douce ( Ipomoea batatas Lam.) est fortement limit\ue9e par les infections virales, en particulier le virus de la marbrure plumeuse de la patate douce et le virus du stunt chlorotique de la patate douce qui provoquent en synergie une maladie virale grave de la patate douce. L\u2019impact des virus est aggrav\ue9 par la nature v\ue9g\ue9tative de la culture et l\u2019inaccessibilit\ue9 des outils fiables pour le diagnostic dans les zones rurales o\uf9 la production de patate douce est r\ue9alis\ue9e. Cela rend difficile les inspecteurs des semences d\u2019effectuer des contr\uf4les de qualit\ue9 avant l\u2019utilisation des vignes par les agriculteurs. L\u2019objectif de cette \ue9tude \ue9tait de d\ue9velopper une proc\ue9dure permettant la d\ue9tection des virus de la patate douce sur place. Cela impliquait une modification de Lodhi et al. (1994) proc\ue9dure d\u2019extraction d\u2019acide nucl\ue9ique, en omettant certaines des \ue9tapes sp\ue9cifiques du laboratoire et en faisant la variation de temps d\u2019incubation dans l\u2019azote liquide, au lieu du cong\ue9lateur. L\u2019incubation dans l\u2019azote liquide pendant seulement 1,5 heure a donn\ue9 un ARN de haute qualit\ue9 comme le protocole d\u2019origine, lorsque l\u2019incubation a \ue9t\ue9 effectu\ue9e \ue0 4 \ub0 C pendant une nuit dans un cong\ue9lateur. La transcriptase inverse (RT) a \ue9t\ue9 faite en utilisant un thermocycleur mini PCR portable et l\u2019ADNc, et r\ue9sultant a \ue9t\ue9 amplifi\ue9 en utilisant cette machine mini PCR au lieu d\u2019utiliser un thermocycleur PCR conventionnel stationn\ue9 en laboratoire. L\u2019ADNc a \ue9t\ue9 efficacement amplifi\ue9 et les amplicons \ue9taient similaires \ue0 ceux obtenus avec le protocole d\u2019extraction original et l\u2019amplification ult\ue9rieure par la RT-PCR conventionnelle. Notre protocole a r\ue9duit le temps d\u2019extraction d\u2019environ 16 heures pour le protocole d\u2019origine, \ue0 environ 2 heures et 45 minutes. Si cet outil est utilis\ue9 par le d\ue9partement de la protection des cultures, nous pensons qu\u2019il contribuera grandement \ue0 la production durable de patate douce en faisant des recommandations en temps opportun

EFFECTIVE ISOLATION DISTANCE FOR PREVENTION OF CASSAVA VIRUS INFECTIONS IN UGANDA

Cassava brown streak disease (CBSD) and cassava mosaic disease (CMD) are the major viral diseases of cassava in Uganda. Although isolation distance of \u201c50 m\u201d has been recommended by MAAIF in Uganda for prevention of virus infections in crops, the minimum isolation distance has not been verified for effectiveness in cassava. This study assessed the effective isolation distance for management of viral diseases in cassava. Virus-clean cassava cultivars (NASE 03, NASE 14 and NAROCASS 1) from farmers\u2019 fields were used as field sourced (FS) planting materials. Tissue culture (TC) material of the same cultivars were sourced from the National Crops Resources Research Institute and Makerere University Agricultural Research Institute tissue culture laboratories. Both FS and TC materials were tested at isolation distances of 50, 100, 150 and 250 m for virus prevention. The experiment was laid out in a randomised complete block design and was run for 12 months after planting (MAP). Mean CBSD/CMD prevalence significantly varied (P<0.05) among isolation distances in both FS and TC plants, and the 250 m isolation distance was the most effective in reducing disease prevalence. Across cultivars and planting material category at 12 MAP, the 50 m isolation distance had the highest foliar incidence for CBSD (29.2%) and CMD (16.1%); while severity for CBSD was 1.4 and 1.2 for CMD. At 250 m, all FS and TC plants had CBSD/CMD severity of 1.0 and 0% incidence. These results show that 250 m isolation distance can provide an option to disseminate popular, but CBSD/CMD susceptible cassava cultivars thereby manage CBSD/CMD.La maladie des stries brunes du manioc (CBSD) et la maladie de la mosa\uefque du manioc (CMD) sont les principales maladies virales du manioc en Ouganda. Bien qu\u2019une distance d\u2019isolement de \uab50 m\ubb ait \ue9t\ue9 recommand\ue9e par le MAAIF en Ouganda pour la pr\ue9vention des infections virales dans les cultures, l\u2019efficacit\ue9 minimale de la distance d\u2019isolement n\u2019a pas \ue9t\ue9 v\ue9rifi\ue9e dans le manioc. Cette \ue9tude a \ue9valu\ue9 la distance d\u2019isolement efficace pour la gestion des maladies virales dans le manioc. Des cultivars de manioc sans virus (NASE 03, NASE 14 et NAROCASS 1) provenant des champs des agriculteurs ont \ue9t\ue9 utilis\ue9s comme le source de mat\ue9riel de plantation (FS). Le mat\ue9riel de culture tissulaire (TC) des m\ueames cultivars provenait des laboratoires National Crops Resources Research Institute and Makerere University Agricultural Research Institute tissue culture. Les mat\ue9riaux FS et TC ont \ue9t\ue9 test\ue9s \ue0 des distances d\u2019isolement de 50, 100, 150 et 250 m pour la pr\ue9vention des virus. L\u2019exp\ue9rience a \ue9t\ue9 pr\ue9sent\ue9e dans un bloc complet randomis\ue9 et a \ue9t\ue9 r\ue9alis\ue9e pendant 12 mois apr\ue8s la plantation (MAP). La pr\ue9valence moyenne de CBSD / CMD variait significativement (P <0,05) entre les distances d\u2019isolement dans les plantes FS et TC, et la distance d\u2019isolement de 250 m \ue9tait la plus efficace pour r\ue9duire la pr\ue9valence de la maladie. \uc0 travers les cultivars et la cat\ue9gorie de mat\ue9riel de plantation \ue0 12 MAP, la distance d\u2019isolement de 50 m avait l\u2019incidence foliaire la plus \ue9lev\ue9e pour le CBSD (29,2%) et le CMD (16,1%); tandis que la gravit\ue9 pour CBSD \ue9tait de 1,4 et 1,2 pour CMD. \uc0 250 m, toutes les plantes FS et TC avaient une gravit\ue9 CBSD / CMD de 1,0 et une incidence de 0%. Ces r\ue9sultats montrent qu\u2019une distance d\u2019isolement de 250 m peut fournir une option pour diss\ue9miner des cultivars de manioc sensibles au CBSD / CMD, ce qui permet de g\ue9rer le CBSD / CMD

Pathogenicity and virulence of Ugandan isolates of common bacterial blight disease pathogen ( Xanthomonas spp.)

Breeding for resistance is a major component in the integrated management of common bacterial disease of beans ( Phaseolus vulgaris L.). Use of less virulent strains or strains with attenuated virulence may lead to selection of resistant genotypes with intermediate response, when exposed to more virulent strains of the pathogen. The objective of this study to identify and characterise Ugandan isolates of common bacterial blight disease-causing pathogens for virulence. Bacteria were isolated from leaf samples collected from districts of Kabale, Masaka, Bukomansimbi, Mubende, Mbale, Bulambuli and Apac, all in Uganda, during the first season of 2016. The bacteria were tested for pathogenicity, as well as virulence on both breeding and local varieties. The study identified three most virulent isolates, namely MBL020, KAB-3 and BUL-14, all belonging to Xathomonas citri pv fuscans. These isolates are very similar to those previously identified from Uganda (NCPB 670 and NCCPB 1402) more than 50 years ago. The study further revealed that NAROBEAN1, NAROBEAN 2, NAROBEAN 4, VAX 3, VAX5 and NE 2- 14- 8 had better resistance compared to other tested genotypes.La s\ue9lection pour la r\ue9sistance est un \ue9l\ue9ment majeur de la gestion int\ue9gr\ue9e des maladies bact\ue9riennes courantes des haricots ( Phaseolus vulgaris L.). L\u2019utilisation de souches moins virulentes ou de souches \ue0 virulence att\ue9nu\ue9e peut conduire \ue0 la s\ue9lection de g\ue9notypes r\ue9sistants \ue0 r\ue9ponse interm\ue9diaire, lorsqu\u2019ils sont expos\ue9s \ue0 des souches plus virulentes du pathog\ue8ne. L\u2019objectif de cette \ue9tude etait d\u2019identifier et de caract\ue9riser les isolats ougandais de pathog\ue8nes causant la maladie bact\ue9rienne commune pour la virulence. Des bact\ue9ries ont \ue9t\ue9 isol\ue9es \ue0 partir d\u2019\ue9chantillons de feuilles pr\ue9lev\ue9s dans les districts de Kabale, Masaka, Bukomansimbi, Mubende, Mbale, Bulambuli et Apac, tous en Ouganda, au cours de la premi\ue8re saison de 2016. Les bact\ue9ries ont \ue9t\ue9 test\ue9es pour leur pathog\ue9nicit\ue9, ainsi que leur virulence \ue0 la fois pour la reproduction et vari\ue9t\ue9s locales. L\u2019\ue9tude a identifi\ue9 les trois isolats les plus virulents, \ue0 savoir MBL020, KAB-3 et BUL-14, tous appartenant \ue0 Xathomonas citri pv fuscans. Ces isolats sont tr\ue8s similaires \ue0 ceux pr\ue9c\ue9demment identifi\ue9s en Ouganda (NCPB 670 et NCCPB 1402), il y a plus de 50 ans. L\u2019\ue9tude a en outre r\ue9v\ue9l\ue9 que NAROBEAN1, NAROBEAN 2, NAROBEAN 4, VAX 3, VAX5 et NE 2- 14-8 avaient une meilleure r\ue9sistance par rapport aux autres g\ue9notypes test\ue9s

Pasting properties of high-quality cassava flour of some selected improved cassava varieties in Tanzania for baking

Open Access ArticlePartial substituting wheat with high-quality cassava flour (HQCF) in bread making would be economically beneficial in Tanzania. However, cassava varieties with the best pasting quality for this use are unknown. In addition, the appropriate time of harvesting the varieties to attain the best pasting quality is also unknown. This study, therefore, aimed at identifying the most appropriate cassava varieties and their appropriate harvesting time that could be used for production of HQCF for baking bread. Nine improved cassava varieties namely Kiroba, Mkuranga1, Pwani, Chereko, Mkumba, Hombolo, Orela, Kizimbani and Kipusa and two local varieties, Albert and Kibandameno were planted in 2020/2021 and 2021/2022 seasons at TARI-Ukiriguru using a split plot design. Harvesting was done at 10 and 12 months after planting (MAP). Pasting characteristics of the HQCF samples were determined at the International Centre of Tropical Agriculture, Dar es salaam, Tanzania using Perten Rapid Visco Analyzer (RVA) Tecmaster equipment, Model: N103802. The results indicated that KIPUSA had the lowest significant setback, while Hombolo had the highest significant setback both at 10 and 12 MAP suggesting that HQCF produced from KIPUSA should be considered for partial substitution of wheat in baking bread that is attractive to consumers

Genome‑wide association studies reveal novel loci for resistance to groundnut rosette disease in the African core groundnut collection

Groundnut is cultivated in several African countries where it is a major source of food, feed and income. One of the major constraints to groundnut production in Africa is groundnut rosette disease (GRD), which is caused by a complex of three agents: groundnut rosette assistor luteovirus, groundnut rosette umbravirus and its satellite RNA. Despite several years of breeding for GRD resistance, the genetics of the disease is not fully understood. The objective of the current study was to use the African core collection to establish the level of genetic variation in their response to GRD, and to map genomic regions responsible for the observed resistance. The African groundnut core genotypes were screened across two GRD hotspot locations in Uganda (Nakabango and Serere) for 3 seasons. The Area Under Disease Progress Curve combined with 7523 high quality SNPs were analyzed to establish marker-trait associations (MTAs). Genome-Wide Association Studies based on Enriched Compressed Mixed Linear Model detected 32 MTAs at Nakabango: 21 on chromosome A04, 10 on B04 and 1 on B08. Two of the significant markers were localised on the exons of a putative TIR-NBS-LRR disease resistance gene on chromosome A04. Our results suggest the likely involvement of major genes in the resistance to GRD but will need to be further validated with more comprehensive phenotypic and genotypic datasets. The markers identified in the current study will be developed into routine assays and validated for future genomics-assisted selection for GRD resistance in groundnut