Occurrence of rice yellow mottle virus resistance breaking isolates in lowland catchment zones of Uganda

Rice (Oryza spp; 2n=24.) production in Uganda and Africa in general, is seriously threatened by the Rice yellow mottle virus disease (RYMVD), a disease caused by Rice yellow mottle virus (RYMV) within the genus Sobemovirus; family Sobemoviridae. This study investigated the existence and distribution of resistance-breaking RYMV pathotype in the three major lowland rice catchment areas in Uganda. Four known rice accessions resistant to Rice yellow mottle virus (RYMV) namely; Gigante, Tog5672, Tog5674 and Tog5681, carrying resistant allele’s rymv1-2, rymv1-4 & RYMV3, rymv1-5 and rymv1-3, respectively, were tested for their response to different RYMV isolates. The isolates were collected from three major lowland rice catchment areas of Doho, Kibimba, and Olweny in Uganda. Out of 100 leaf samples collected from the field and assayed for RYMV and confirmed to be positive using RT-PCR, 83 isolates induced symptoms on IR64- the RYMV susceptible line. Seventy-seven (92.8%) isolates were able to overcome resistance in at least one of the four differential rice accessions, as confirmed by the presence of RYMV symptoms; while 6 (7.2%) isolates were asymptomatic. Variation in time (days) for symptom development post-inoculation (dpi) and AUDPC were observed. Symptoms appeared within 5-7 days on IR64; while it took on average 11, 18, 36, and 18 days to appear on Gigante, Tog5672, Tog5674 and Tog5681, respectively. The highest AUDPC was observed on IR64 (254.7); while the lowest was observed on Tog5681 (74.1). Two major patho-groups were observed; those that broke down resistance in Gigante only (25.3%) and Gigante & Tog5672 (33.7%). Five isolates from Doho (Budaka & Bugiri districts) and Kibimba (Butaleja district) catchment areas broke down RYMV resistance in three accessions i.e. (Tog5681, Gigante & Tog5672) and (Tog5674, Gigante & Tog5672), respectively. Resistance breaking isolates were confirmed in all  the three sampled catchment zones, however, Doho and Kibimba had some unique isolates that broke down resistance in accessions carrying resistance allele rymv 1-3 and rymv1-5 in addition to rymv1-2. Results from this study showed that RYMV isolates in Uganda can break down resistance conferred by the rymv1-2 resistance gene allele. However, accessions Tog5681 and Tog5674 seem to hold stable RYMV resistance and, thus are recommended for RYMV breeding

Occurrence of rice yellow mottle virus resistance breaking isolates in lowland catchment zones of Uganda

Rice ( Oryza spp; 2n=24.) production in Uganda and Africa in general, is seriously threatened by the Rice yellow mottle virus disease (RYMVD), a disease caused by Rice yellow mottle virus (RYMV) within the genus Sobemovirus; family Sobemoviridae. This study investigated the existence and distribution of resistance-breaking RYMV pathotype in the three major lowland rice catchment areas in Uganda. Four known rice accessions resistant to Rice yellow mottle virus (RYMV) namely; Gigante, Tog5672, Tog5674 and Tog5681, carrying resistant allele\u2019s rymv1-2, rymv1-4 & RYMV3, rymv1-5 and rymv1-3, respectively, were tested for their response to different RYMV isolates. The isolates were collected from three major lowland rice catchment areas of Doho, Kibimba, and Olweny in Uganda. Out of 100 leaf samples collected from the field and assayed for RYMV and confirmed to be positive using RT-PCR, 83 isolates induced symptoms on IR64- the RYMV susceptible line. Seventy-seven (92.8%) isolates were able to overcome resistance in at least one of the four differential rice accessions, as confirmed by the presence of RYMV symptoms; while 6 (7.2%) isolates were asymptomatic. Variation in time (days) for symptom development post-inoculation (dpi) and AUDPC were observed. Symptoms appeared within 5-7 days on IR64; while it took on average 11, 18, 36, and 18 days to appear on Gigante, Tog5672, Tog5674 and Tog5681, respectively. The highest AUDPC was observed on IR64 (254.7); while the lowest was observed on Tog5681 (74.1). Two major patho-groups were observed; those that broke down resistance in Gigante only (25.3%) and Gigante & Tog5672 (33.7%). Five isolates from Doho (Budaka & Bugiri districts) and Kibimba (Butaleja district) catchment areas broke down RYMV resistance in three accessions i.e. (Tog5681, Gigante & Tog5672) and (Tog5674, Gigante & Tog5672), respectively. Resistance breaking isolates were confirmed in all \ua0the three sampled catchment zones, however, Doho and Kibimba had some unique isolates that broke down resistance in accessions carrying resistance allele rymv 1-3 and rymv1-5 in addition to rymv1-2. Results from this study showed that RYMV isolates in Uganda can break down resistance conferred by the\ua0rymv1-2 resistance gene allele. However, accessions Tog5681 and Tog5674 seem to hold stable RYMV resistance and, thus are recommended for RYMV breeding.La production de riz ( Oryza spp ; 2n=24.) en Ouganda et en Afrique en g\ue9n\ue9ral, est s\ue9rieusement menac\ue9e par la maladie du virus de la marbrure jaune du riz (RYMVD), une maladie caus\ue9e par le virus de la marbrure jaune du riz (RYMV) du genre Sobemovirus ; famille des Sobemoviridae. Cette \ue9tude a examin\ue9 l\u2019existence et la distribution du pathotype RYMV qui brise la r\ue9sistance dans les trois principaux bassins versants de riz de plaine en Ouganda. Les quatre accessions de riz connues r\ue9sistantes au \ua0virus\ua0de la panachure\ua0jaune du riz\ua0(RYMV, Rice yellow mottle\ua0virus) \ue0 savoir; Gigante, Tog5672, Tog5674 et Tog5681, portant respectivement les all\ue8les r\ue9sistants rymv1-2, rymv1-4 & rymv3, rymv1-5 et rymv1-3, ont \ue9t\ue9 test\ue9s pour leur r\ue9ponse \ue0 diff\ue9rents isolats de RYMV. Les isolats ont \ue9t\ue9 collect\ue9s dans les trois principaux bassins versants du riz de plaine de Doho, Kibimba et Olweny en Ouganda. Sur les 100 \ue9chantillons des feuilles pr\ue9lev\ue9s sur le terrain et test\ue9s pour le RYMV et confirm\ue9s positifs par RT-PCR, 83 isolats ont induit des sympt\uf4mes sur IR64, la lign\ue9e sensible au RYMV. Les soixante-dix-sept (92,8 %) isolats ont r\ue9ussi \ue0 surmonter la r\ue9sistance dans au moins une des quatre accessions du riz diff\ue9rentielles, comme le confirme la pr\ue9sence des sympt\uf4mes du RYMV\ua0; tandis que 6 (7,2 %) isolats \ue9taient asymptomatiques. Une variation dans le temps (jours) pour le d\ue9veloppement des sympt\uf4mes apr\ue8s l\u2019inoculation (dpi, development post-inoculation) et l\u2019AUDPC a \ue9t\ue9 observ\ue9e. Les sympt\uf4mes sont apparus dans les 5 \ue0 7 jours sur IR64\ua0; alors qu\u2019il a fallu en moyenne 11, 18, 36 et 18 jours pour appara\ueetre sur Gigante, Tog5672, Tog5674 et Tog5681, respectivement. L\u2019AUDPC le plus \ue9lev\ue9 a \ue9t\ue9 observ\ue9 sur IR64 (254,7); tandis que l\u2019AUDPC le plus bas a \ue9t\ue9 observ\ue9 sur Tog5681 (74,1). Deux patho-groupes principaux ont \ue9t\ue9 observ\ue9s; ceux qui ont bris\ue9 la r\ue9sistance dans les Gigante uniquement (25,3%) et Gigante & Tog5672 (33,7%). Les cinq isolats des bassins versants de Doho (districts de Budaka et Bugiri) et de Kibimba (district de Butaleja) ont bris\ue9 la r\ue9sistance au RYMV dans trois accessions, \ue0 savoir (Tog5681, Gigante et Tog5672) et (Tog5674, Gigante et Tog5672), respectivement. Des isolats brisant la r\ue9sistance ont \ue9t\ue9 confirm\ue9s dans les trois zones de captage \ue9chantillonn\ue9es, cependant, Doho et Kibimba avaient des isolats uniques qui brisaient la r\ue9sistance dans des accessions portant les all\ue8les de r\ue9sistance rymv1-3 et rymv1-5 en plus de rymv1-2. Les r\ue9sultats de cette \ue9tude ont montr\ue9 que les isolats de RYMV en Ouganda peuvent briser la r\ue9sistance conf\ue9r\ue9e par l\u2019all\ue8le du g\ue8ne de r\ue9sistance rymv1-2. Cependant, les accessions Tog5681 et Tog5674 semblent d\ue9tenir une r\ue9sistance stable au RYMV et sont donc recommand\ue9es pour la s\ue9lection du RYMV

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

Practices and constraints of tomato production among smallholder farmers in Uganda

Tomato (Solanum esculentum) is one of the most promising vegetables whose production is being intensified in Uganda. However, tomato yields remain low due to several constraints. The study aimed at identifying production and marketing practices, and constraints affecting tomato productivity in major tomato growing areas of Uganda. A survey was conducted in eight major tomato producing districts using a questionnaire to guide interviews for 240 farmers and 16 key informants. The data were analyzed using SPSS software. Results revealed that tomato production in Uganda is dominated by males who grow them on 0.68 acres of land on average. Most tomato farmers (78.4%) use mono cropping system with varieties Asilla F1 (35.3%), Tengeru97 (21.1%), Rambo (18.1%), Novela F1 (17.7%) and Riogrande (10.3%) dominating. The choice of tomato varieties used by farmers mainly depend on yield potential, pest and disease tolerance and market preference attributes such as long shelf life. In the study area, tomato is mainly fertilized using foliar fertilizers, followed by Diammonium phosphate and cattle manure. The key pests affecting tomato include caterpillars, thrips, worms and whitefly, while bacterial wilt, blight, leaf spots and viral infections are the major diseases. Majority (95.7%) of farmers use chemical sprays (pesticides and fungicides) and 4.3% of farmers used other control methods. The other methods of pest and disease control included rogueing, hand picking, ash, organic extracts, urine and frequent weeding. Average tomato yield was 4,846.3 kg/acre lower than the potential yield of 6000kg/acre. Thirty five percent of farmers market their tomato individually on-farm, 32.8% sell in rural markets, while 32.2% send to the nearest urban markets. The study revealed intensive chemical use accounting for 20% of the production costs, high seed costs (11%) and drought (10%) as the major production constraints impeding tomato production; and price fluctuations, low prices, high transport costs, post-harvest loss on farm, and poor market access as the major marketing constraints. The research findings will aid in the development of new market-oriented, highly productive tomato varieties with improved access to seed and designing initiatives to address production and marketing constraints, which will eventually enhance tomato production

Use of DNA capture kits to collect Xanthomonas campestris pv. musacearum and banana bunchy top virus pathogen DNA for molecular diagnostics

Banana Xanthomonas wilt, caused by the bacterium Xanthomonas campestris pv. musacearum, and banana bunchy top virus disease (BBTD), caused by the banana bunchy top virus (BBTV), are two of the most devastating diseases of banana in East and Central Africa, and cause significant losses in food security and income for millions of farmers, traders and consumers. To prevent the establishment and spread of the diseases across the region, control interventions must be rapidly deployed. A first and critical step towards deployment of appropriate disease management strategies is the rapid and precise diagnosis of the causal agent of disease. The diagnosis of Xanthomonas wilt in the field based on disease symptoms is often confused with another disease that causes wilting that is due to the fungus Fusarium oxysporum f.sp. cubense, so diagnostic tools that are easy to use, cost-effective and reliable are required to help field workers. BBTD symptoms can also be confused with nutrient deficiencies or varietal differences. To this end, three types of portable kits were evaluated for their performance in capturing pathogen DNA from the field for use in precise, molecular-based pathogen diagnostics under controlled laboratory conditions. All three prototypes tested – FTA cards, the PhytoPASS kit and two-minute DNA extraction dipsticks – gave excellent results and methods were optimized for sample collection in the field, DNA extraction and PCRbased diagnostics for X. campestris pv. musacearum and BBTV. The benefits of using DNA capture kits included: collection of pathogen DNA in a cheap and practical manner, safe and fast transfer of high integrity pathogen DNA across country borders, rapid and precise diagnosis using state-of-the-art molecular technologies and direct comparison of results from geographically diverse samples. This is possible because analysis is performed in a uniform manner in terms of method, date, equipment, reagents and technical staff. Technical support was provided to workers in the field to help them differentiate symptoms based on diagnostic results from laboratory analyses; such support could also be provided to regulatory officials at borders to ensure that, for example, planting material is free from disease. Countries involved in testing the DNA capture kits for X. campestris pv. musacearum included Burundi, Democratic Republic of Congo (DR Congo), Kenya, Rwanda, Tanzania and Uganda. The same countries, with Zambia also included, were also tested for BBTV. While no positive results for X. campestris pv. musacearum were obtained from samples originating from surveys in Burundi, subsequent DNA capture kits from samples from Bubanza and Cankuzo provinces did test positive, thus confirming an outbreak of Xanthomonas wilt in this country. BBTV was confirmed in DR Congo, Burundi, Rwanda and Zambia