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

Production of friable embryogenic callus and regeneration of Ugandan farmer-preferred cassava genotypes

Generation of embryogenic callus is a key step in genetic engineering of many crop species, including cassava. Protocols for generation of friable embryogenic callus (FEC) have been lacking for Ugandan cassava genotypes, thereby delaying their genetic engineering for agronomic and other desirable traits. The objective of this study was to determine conditions suitable for production and regeneration of FEC in the Ugandan cassava genotypes; Aladu, Bukalasa and Ebwanateraka, and control cultivar 60444. Immature leaf lobe explants were established on Murashige and Skoog (MS) based media for initiation of organized embryogenic callus (OES). To produce FEC, resulting OES were established on Gresshoff and Doy based callus induction media with varying levels of sucrose, maltose, tyrosine, tryptophan, naphthalene acetic acid (NAA) under light and dark conditions. Subsequently, FEC was subcultured to MS-based embryo maturation and embryo regeneration media. All genotypes produced OES. All genotypes produced FEC except Bukalasa. The amino acid tyrosine favoured production of FEC in Aladu and Ebwanatereka, but not in 60444, while 20 g/L of sucrose trigged production of FEC in Aladu and 60444, but 40 g/L of sucrose was superior for Ebwanatereka. Media supplemented with 1 ml/L naphthalene acetic acid NAA facilitated embryo regeneration in Ebwanatereka and 60444, while Aladu responded better to 5 ml/L NAA. Light, tyrosine and sucrose were essential for FEC production in Uganda cultivars while NAA was required for regeneration of somatic embryos. Ability to produce FEC in these genotypes lays a foundation for their improvement through genetic transformation for the desired and agronomic traits.Key words: Cassava (Manihot esculenta Crantz), somatic embryogenesis, amino acids, carbon sources

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

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

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<0.001), but reduced biomass (r = -0.70, P<0.001) and height (r = -0.88, P<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<0.001) mais avec de la biomasse (r = -0.70, P<0.001) et hauteur (r = -0.88, P<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

CASSAVA BROWN STREAK DISEASE EFFECTS ON LEAF METABOLITES AND PIGMENT ACCUMULATION

Cassava Brown Streak Disease (CBSD) is a threat to productivity and product quality in East Africa. The objective of this study was to understand the effect of CBSD on the primary photosynthetic apparatus of cassava ( Manihot esculenta Crantz). Three cassava varieties with varying levels of reaction to infection by CBSD were chosen and subjected to field disease pressure. Disease progression and the resulting effects on leaf morphology, metabolite and pigment accumulation were assessed over a period of five months, beginning from 3 months after planting. Slight increments in leaf dry matter were observed up to 4 MAP, and there after a drop was registered. A significant (P<0.05) reduction in photosynthetic pigments occured with a fall in the Chla:Chlb and Chla:Carotenoid ratio, indicative of specific reductions in chlorophyll a (-80%) compared to Chlorophyll b (-41 to -62%) and Carotenoid (-11 to -18%). Total reducing sugar and starch content also dropped significantly (-30 and -60%, respectively), much as NASE 14 maintained a relatively higher amount of carbohydrates. Leaf protein levels were significantly reduced at a rate of 0.07 ug g-1 leaf per month in diseased treatments. Significant reductions in primary metabolites show altered leaf photosynthetic and growth metabolism, resulting into a compromised plant system that cannot perform optimally.La Maladie Stri\ue9e Brune du Manioc (CBSD) constitue une menace pour la productivit\ue9 et la qualit\ue9 des produits du manioc en Afrique de l\u2019Est. L\u2019objectif de cette \ue9tude \ue9tait de comprendre l\u2019effet de CBSD sur l\u2019appareil photosynth\ue9tique primaire du manioc ( Manihot esculenta Crantz). Trois vari\ue9t\ue9s de manioc poss\ue9dant differents niveaux de r\ue9sistance \ue0 CBSD ont \ue9t\ue9 soumises \ue0 la pression dans les conditions de plein champs. La progression de la maladie et son effet sur la morphologie foliaire, les metabolites et accumulations de pigments ont \ue9t\ue9 \ue9valu\ue9s sur une p\ue9riode de cinq mois, \ue0 compter du troisi\ue8me mois apr\ue8s semis. Il a \ue9t\ue9 observ\ue9e une l\ue9g\ue8re augmentation de mati\ue8re s\ue8che foliaire jusqu\u2019\ue0 4 MAP, suivie d\u2019une chute. Une r\ue9duction significative (P<0,05) des pigments photosynth\ue9tiques a \ue9t\ue9 observ\ue9e avec une chute dans le Chla:Chlb et Chla:ratio de Carotenoide, indiquant des r\ue9ductions sp\ue9cifique sen chlorophyllea (-80%) en comparaison avec la Chlorophylleb (-41 \ue0 -62%) et les Carotenoides (-11 \ue0 -18%). La r\ue9duction du sucre et d\u2019amidona connu aussi une diminution significative (-30 et -60%, respectivement), de m\ueame NASE 14 a maintenuun equantit\ue9 relativement\ue9 lev\ue9e d\u2019hydrates de carbone. Les niveaux de proteines foliaires \ue9taient significativement r\ue9duits \ue0 0,07 ug g-1 de feuille malade par mois. Des r\ue9ductions significatives des metabolites primaires sont \ue0 l\u2019origne de l\u2019alt\ue9ration du m\ue9tabolisme photosynth\ue9tique et de croissance, resultant \ue0 cycle v\ue9g\ue9tatif compromis qui ne peut permettre un d\ue9veloppement optimal de la plante

Phenotypic diversity within Ugandan yam (Dioscorea species) germplasm collection

Open Access JournalA proper understanding of the diversity of the available germplasm is an initial step for the genetic improvement of a crop through breeding. However, there is limited information on the diversity of Uganda’s yam germplasm. The study sought to characterize the diversity of yam germplasm utilized for decades in Uganda together with germplasm recently introduced from West Africa using phenotypic traits. A germplasm collection of 291 genotypes was characterized using 28 phenotypic traits. Data were subjected to multivariate analysis using principal component analysis and cluster analysis. The traits assessed were informative and discriminating, with 62% of the total variation explained among the first six principal components. Results showed that the important phenotypic traits contributing to most of the variability among the genotypes were leaves, flowering, and tuber traits. Ugandan genotypes were identified with amorphous tuber shapes compared to West African genotypes. The study has shown that there is ample phenotypic variability within the major yam genotypes in Uganda yam germplasm that can be used for genetic improvement. More in-depth molecular and biochemical studies to further understand the diversity are recommended. The preprint was made available by research square in the following link: “https://www.researchsquare.com/article/rs-1518551/v1.

Validation of KASP markers associated with cassava mosaic disease resistance, storage root dry matter and provitamin A carotenoid contents in Ugandan cassava germplasm

Open Access Journal; Published online: 23 Nov 2022Introduction The intrinsic high heterozygosity of cassava makes conventional breeding ineffective for rapid genetic improvement. However, recent advances in next-generation sequencing technologies have enabled the use of high-density markers for genome-wide association studies, aimed at identifying single nucleotide polymorphisms (SNPs) linked to major traits such as cassava mosaic disease (CMD) resistance, dry matter content (DMC) and total carotenoids content (TCC). A number of these trait-linked SNPs have been converted to Kompetitive allele-specific polymerase chain reaction (KASP) markers for downstream application of marker assisted selection. Methods We assayed 13 KASP markers to evaluate their effectiveness in selecting for CMD, DMC and TCC in 1,677 diverse cassava genotypes representing two independent breeding populations in Uganda. Results Five KASP markers had significant co-segregation with phenotypes; CMD resistance (2), DMC (1) and TCC (2), with each marker accounting for at least 30% of the phenotypic variation. Markers located within the chromosomal regions for which strong marker-trait association loci have been characterised (chromosome 12 markers for CMD, chromosome 1 markers for DMC and TCC) had consistently superior ability to discriminate the respective phenotypes. Discussion The results indicate varying discriminatory abilities of the KASP markers assayed and the need for their context-based use for MAS, with PSY2_572 particularly effective in selecting for high TCC. Availing the effective KASP markers on cost-effective genotyping platforms could facilitate practical implementation of marker-assisted cassava breeding for accelerated genetic gains for CMD, DMC and provitamin A carotenoids

Effects of gamma irradiation and ethyl methane sulphonate on morphometric traits and prevalence of common viral diseases and whiteflies in cassava

Cassava ( Manihot esculenta Crantz) is an important staple and food security crop for millions of people in Africa. However, its nutritional value is limited; yet its productivity is constrained by several pests and diseases. Induced mutagenesis is one approach with the potential to overcome such biotic stresses. The objective of this study was to assess the variability in morphometric traits and prevalence of common viral diseases and whiteflies in cassava to different doses and concentrations of gamma irradiation and ethyl methane sulphonate (ems) treatments. The effects were assessed on seed germination and growth of stakes, as well as foliar viral disease symptoms and whitefly counts. Radio-sensitivity tests revealed LD50 for sprouting as 37.6Gy for \u3b3-irradiation and 0.08% for EMS treatment. There was notable decrease in sprout, epicotyl length, shoot height, petiole length and number of leaf lobes, with increasing \u3b3-ray doses and EMS concentrations. Contrastingly, total chlorophyll content increased with increasing doses of \u3b3-rays and EMS concentrations. Basing on foliar whitefly counts and disease symptoms, there was a general increase in susceptibility to whitefly infestation and cassava mosaic disease (CMD) incidence. Significantly varying levels of resistance or tolerance to whiteflies and CMD were observed among plantlets derived from irradiated and EMS treated stems, compared to the controls. These findings lay a foundation for more future research on breeding for various traits, including disease resistance in cassava using induced mutagenesis approach.Le manioc ( Manihot esculenta Crantz) est une culture de base et de la s\ue9curit\ue9 alimentaire importante pour des millions de personnes en Afrique. Cependant, sa valeur nutritionnelle est limit\ue9e; pourtant, sa productivit\ue9 est limit\ue9e par plusieurs ravageurs et maladies. La mutagen\ue8se induite est une approche ayant le potentiel de surmonter de tels stress biotiques. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer la variabilit\ue9 des traits morphom\ue9triques et la pr\ue9valence des maladies virales courantes et des aleurodes du manioc en raison de l\u2019exposition \ue0 diff\ue9rentes doses et concentrations des traitements par l\u2018 irradiation gamma et \ue9thyl m\ue9thane sulfonate (EMS). Les effets ont \ue9t\ue9 \ue9valu\ue9s sur la germination des graines et la croissance des tuteurs, ainsi que sur les sympt\uf4mes de la maladie virale foliaire et le nombre des aleurodes. Les tests de radiosensibilit\ue9 ont r\ue9v\ue9l\ue9 que la DL50 pour la germination \ue9tait de 37,6 Gy pour l\u2019irradiation et de 0,08 % pour le traitement EMS. Il y avait une diminution notable de la pousse, de la longueur de l\u2019\ue9picotyle, de la hauteur des pousses, de la longueur du p\ue9tiole et du nombre des lobes foliaires, avec l\u2019augmentation des doses de rayons et des concentrations EMS. En revanche, la teneur totale en chlorophylle augmentait avec l\u2019augmentation des doses de rayons et des concentrations EMS. Sur la base des d\ue9nombrements foliaires des aleurodes et des sympt\uf4mes de la maladie, il y avait une susceptibilit\ue9 g\ue9n\ue9ralement accrue \ue0 l\u2019infestation des aleurodes et \ue0 l\u2019incidence de la maladie de la mosa\uefque du manioc (CMD). Des niveaux significativement variables de r\ue9sistance ou de tol\ue9rance aux aleurodes et \ue0 la CMD ont \ue9t\ue9 observ\ue9s parmi les plantules d\ue9riv\ue9es de tiges irradi\ue9es et trait\ue9es par EMS, par rapport aux t\ue9moins. Ces r\ue9sultats jettent les bases des autres recherches futures sur la s\ue9lection pour les divers caract\ue8res, y compris la r\ue9sistance aux maladies du manioc en utilisant une approche de mutagen\ue8se induite