71 research outputs found
Genetic homogeneity among Ugandan isolates of Xanthomonas campestris pv. musacearum revealed by randomly amplified polymorphic DNA analysis
The Random Amplification of Polymorphic DNA (RAPD) analysis was used to detect the genetic diversity among Ugandan isolates of Xanthomonas campestris pv. musacearum (Xcm), the causal agent of banana Xanthomonas wilt (BXW) disease. Seven random primers were used because of their ability to amplify reproducible and reliable fingerprints generated between 6 - 12 amplicons each from the Xcm isolates obtained from central core of pseudostems, peduncles, fruit peelings, sap, nectar,insects’ bodies and bacterial oozes. Regardless of the source and geographical origin, similar fingerprints were generated from the tested isolates. Using a similarity coefficient of 58%, the unweighted pair group method with arithmetic averaging (UPGMA) analysis did not reveal anysignificant differences in clustering, with exception of a single isolate that had unique fingerprints. Prior to the genetic analysis, all the isolates compared showed no significant difference (P = 0.92) with regardto incubation period for appearance of symptoms and the severity of symptoms in pathogenicity test. Thus, our data indicates that the population of Xcm in Uganda is clonal, that is, one uniform populationbeing spread fast and efficiently, suggesting that there is a low likelihood of the current population to rapidly evolve, in the near future, into more virulent strains to overcome any resistance deployed
Spatial and temporal distribution of insect vectors of Xanthomonas campestris pv. musacearum and their activity across banana cultivars grown in Rwanda.
Insect vectors of Xanthomonas campestris pv musacearum (Xcm) have played a major role
in long distance and plant to plant transmission of Xanthomonas wilt of banana (XW). The
prevalence of insects has been reported to vary in space and time. Some banana cultivars have
also been reported to attract more insect vectors of Xcm than others. The present study was
conducted to determine the spatial and temporal distribution of insect vectors of Xcm and
assess their activity across banana cultivars grown in Rwanda. The study was carried out in four
banana growing areas of Rwanda selected on the basis of their altitude (i.e.Low, Medium and
High). The Kivu Lake Border region was selected as a fourth site due to the high prevalence of
XW. Insects were sampled in the four annual seasons (short dry, short rainy, long dry and long
rainy) and at different times of the day. During sampling of insects, the incidence of XW-male
bud infection was also recorded. Collected insects were immediately sorted into taxonomic
groups and conserved in vials containing 70% ethanol for further identification to genus and
species level. Five insect specimens in each taxon were put aside for the isolation of Xcm on
their external body parts. There was a high prevalence of fruit flies, honey bees and other flies
(in other families than Drosophilidae and Tephritidae) compared with wasps, ants and beetles.
More insects were recorded in the low altitude area and during the long rainy season. These
findings correlated with the observed high incidence of XW in the wet seasons. Incidence of floral
infections was higher in the low altitudes declining with the increase in altitude, correlating with
the decline in insect activity as altitude increased. The activity of insects on banana male buds
varied among banana cultivars, with more activity on beer (AAA-East African Highland (EAH)
and ABB types) and dessert banana cultivars compared with cooking or mixed use cultivars.
Among the cooking types only ‘Injagi’ and its clone sets ‘Barabeshya’ and ‘Incakara’ attracted
large insect populations. Banana cultivars ‘Nkazikamwe’ (cooking AAA-EAH), ‘Impura’ (beer AAAEAH)
and ‘Ikinyangurube’ (dessert AAA) possessed persistent male bracts and neuter flowers
and were less attractive to flower visitors. These cultivars could be promoted in areas prone to
insect vector infections. Timely and proper de-budding should be emphasized with special
attention during the rainy seasons and for banana cultivars with non-persistent male buds
Studies of the genetics of inheritance of stem rust resistance in bread wheat
Pgt race TTKSK (Ug99) has a wide virulence range with respect to currently grown wheat cultivars worldwide. Aspects of migration, mutation, recombination and selection in the pathogen have led to previously deployed stem rust resistance genes being ineffective. Race TTKSK has further evolved to acquire virulence for resistance genes such as Sr24 (race Ug99 + Sr24) and Sr36 (Ug99 + Sr36). Five resistant wheat lines (KSL-2, KSL-3, KSL-5, KSL-12 and KSL-19) which were resistant in tests during 2008, 2009 and 2010 were used as parents in crosses with stem rust susceptible line CACUKE to develop genetic populations for determining the inheritance of resistance to stem rust. F3 populations were evaluated at KARI Njoro in the 2012 off season and 2012 to 2013 main season. The adult plant stem rust responses were scored using the modified Cobb’s scale. The F2:3 lines of population(s) exhibiting qualitative variation were grouped as homozygous resistant (HR), segregating (Seg) and homozygous susceptible (HS). Heavy disease pressure was present during the cropping seasons with the check CACUKE displaying 90% susceptibility. Chi square analysis revealed that the segregation data in the parent KSL-2 did not deviate significantly from the single gene model (1:2:1) suggesting that the resistance to stem rust is conditioned by a single dominant gene. The Chi square test also revealed that the stem rust resistance in the parents KSL-3, KSL-5, KSL-12 and KSL-19 was conditioned by two genes. The families from the KSL-2 and KSL-3 crosses also segregated for the presence of the pseudo black chaff implying that the Sr2 gene could be present in the background of these wheat parents. The superior transgressive segregants identified in these crosses will be used in breeding.Keywords: Genetic, wheat, gene, resistanceAfrican Journal of Biotechnology Vol. 12(21), pp. 3153-315
Variation in nectar volume and sugar content in male flowers of Musa cultivars grown in Rwanda and their non-effect on the numbers of visiting key diurnal insect vectors of banana Xanthomonas wilt
Insects are a major mode of banana Xanthomonas wilt (XW) spread. High insect activity has been blamed for the high XW incidence in ‘Kayinja’ (ABB-genome) dominated banana landscapes across east and central Africa. ‘Kayinja’ male bud nectar composition reportedly contributes to high insect activity. The variation in nectar composition with agro-ecological zones and banana cultivars and its influence on the number of visiting insects in Rwanda were assessed. Three male buds were collected per cultivar for nectar extraction and analysis using a high performance liquid chromatography. Nectar volume and sugar concentrations varied (P<0.001) across 27 banana cultivars, annual seasons and agro-ecological zone. The highest nectar volume was recorded among the East African highland cooking cultivars (AAA-genome) in the high altitude site and the short-heavy rainy season. Nectar contained three sugars: glucose, fructose and sucrose, though hexose (glucose and fructose) was dominant. The three sugars varied significantly (P<0.001) within each cultivar. The total nectar-sugar concentration ranged from 2.3–32%, with the highest among dessert cultivars ‘Kamaramasenge’ (AAB-genome) and ‘Gisukari’ (AAA-genome). No strong correlation occurred between insect population and total nectar sugar concentration or nectar volume. Insect populations were rather influenced by the weather conditions, the long rainy season characterized by moderate well distributed rainfall recording the highest insect populations as compared to the short rainy season (with heavy rainfall) and the dry seasons
Prevalence of viruses infecting cowpea in Uganda and their molecular detection
The main areas for cowpea cultivation in Uganda were surveyed in June and October 2006 for viruses affecting the crop. Seed and leaf samples from symptomatic and asymptomatic plants were collected from farmers’ fields and analysed for infecting viruses using double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). The viruses detected in the leaf and seed samples were: cucumber mosaic cucumovirus (CMV), cowpea mild mottle calarvirus (CPMMV), cowpea mottle carmovirus (CPMoV), Cowpea chlorotic mottle bromovirus (CCMV), Cowpea yellow mosaic comovirus (CYMV), cowpea severe mosaic comovirus (CPSMV), cowpea aphid-borne mosaic potyvirus (CABMV) and Southern bean mosaic sobemovirus (SBMV). CPMV was detected only in leaf samples. CMV and CABMV were later confirmed using reverse transcription polymerase chain reaction (RT-PCR). Of the viruses detected in leaf samples, 53.26% occurred as single infections, 24.46% dual and 22.28% multiple infections. Similarly, analysis of seed samples revealed infection of 40.6, 34.6 and 24.8% for single, dual and multiple infections, respectively. Multiple virus infections were associated with more disease severity and higher yield losses. The seed transmission levels of 23.0, 20.3 and 16.4% were recorded for CMV, CPMMV and CABMV, respectively. This study identified six more viruses in addition to what was previously reported in the country, of which eight were seed-borne. This necessitates the need for the production and use of virus-free seeds, development of virus resistant genotypes and adoption of efficient seed certification systems.Keywords: Vigna unguiculata, disease incidence, seed-borne viruses, ELISA, (RT-PCR
Distribution of common bacterial blight disease under different agroecologies in Uganda
Common bacterial blight disease (CBB) causes severe yield and seed
quality losses on common bean worldwide. Information about CBB
distribution is important in designing effective control strategies.
This disease has been managed using intergraded strategies, involving
use of certified seed produced in areas of low disease pressure.
Unfortunately, areas of low CBB pressure have not been mapped in
Uganda. This study was conducted to determine the distribution and
intensity of CBB in Uganda, in order to establish low pressure areas
for multiplication of clean certified seed. A survey was conducted in
farmers\u2019 fields in18 locations found in four rainfalls-based
agroecology in Uganda, for two seasons of 2016. The Victoria Cresent
and Mbale farmland had the highest disease intensity index (29%);
followed by Central woodland savannah (21%). The Northwest farm land
and South west grass farm lands had low CBB intensity index of 2.5 and
7.8%, respectively. Thus, The Northwest farm land (Arua, Amuru, Nwoya)
and South west grass farm lands (Rakai, Ntungamo Lwengo and
Bukomansimbi), are recommended for production of CBB free bean seeds.La maladie bact\ue9rienne commune (MBC) provoque de graves pertes de
rendement et de qualit\ue9 des semences de haricot commun dans le
monde entier. Les informations sur la distribution du MBC sont
importantes pour la conception de strat\ue9gies de contr\uf4le
efficaces. Cette maladie a \ue9t\ue9 g\ue9r\ue9e \ue0
l\u2019aide de strat\ue9gies intercal\ue9es, impliquant
l\u2019utilisation de semences certifi\ue9es produites dans des
zones de faible pression de la maladie. Malheureusement, les zones de
faible pression du CBB n\u2019ont pas \ue9t\ue9
cartographi\ue9es en Ouganda. Cette \ue9tude a \ue9t\ue9 faite
pour d\ue9terminer la distribution et l\u2019intensit\ue9 du CBB
en Ouganda, afin d\u2019\ue9tablir des zones de basse pression pour
la multiplication de semences certifies qui sont propres. Une
enqu\ueate a \ue9t\ue9 faite dans les champs d\u2019agriculteurs
dans 18 localit\ue9s situ\ue9es dans quatre agro\ue9cologies en
Ouganda bas\ue9es sur les pr\ue9cipitations, pendant les deux
saisons de 2016. Les terres agricoles de Victoria Cresent et de Mbale
pr\ue9sentaient l\u2019indice d\u2019intensit\ue9 de maladie le
plus \ue9lev\ue9 (29%); suivi de la savane bois\ue9e centrale
(21%). Les terres agricoles du nord-ouest et celles du sud-ouest
avaient un indice d\u2019intensit\ue9 de CBB faible de 2,5 et 7,8%,
respectivement. Ainsi, les terres agricoles du Nord-Ouest (Arua, Amuru,
Nwoya) et celles du Sud-Ouest (Rakai, Ntungamo Lwengo et Bukomansimbi)
sont recommand\ue9es pour la production de semences de haricot
exemptes de CBB
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
INHERITANCE OF ROOT DRY MATTER CONTENT IN SWEETPOTATO
There has been much emphasis on breeding for increased sweetpotato
storage root yield, but less on dry matter yield, and its inheritance.
High dry matter content (DMC) is associated with consumer preferences,
and is important for the processing industry. This study was conducted
to determine the type of gene action controlling DMC and to assess
genotype by environment (G x E) interaction effect on DMC in
sweetpotato. Five parental clones varying in DMC were hand-crossed in a
half-diallel design to generate ten families. Ten genotypes of each
family were planted in a trial at Namulonge (swamp and upland
environments) and Serere in Uganda in 2009 and 2010. Highly significant
(P<0.001) differences were found both between genotypes and between
families for DMC. High significant general combining ability (GCA)
(P<0.001) and specific combining ability (SCA) (P<0.01) were
obtained, meaning that the differences among families for high DMC were
due to both GCA and SCA. The relative importance of GCA and SCA was
0.59, indicating that additive gene action was slightly more
predominant than non-additive gene action in predicting progeny
performance for high DMC. Broad sense heritability (H) estimates for
DMC were 0.70 and 0.73, respectively on genotype and family means
across environments basis, suggesting that DMC was moderately
influenced by the environment. Rapid selection for best genotypes would
be possible, since progenies can be predicted from the phenotype of the
parents. Parent SPK (GCA = 1.02) was the best combiner. The effect of
location was less significant compared to seasons, suggesting the need
to evaluate genotypes for several seasons, but in few locations to save
resources.Plusieurs efforts ont \ue9t\ue9 fournis dans le cadre
d\u2019augmenter le rendement de la patate douce, mais peu
d\u2019efforts visant le rendement sec et son h\ue9ritabilit\ue9.
La mati\ue8re s\ue8che est associ\ue9e aux pr\ue9f\ue9rences
des consommateurs et elle est importante dans l\u2019industrie de
transformation. Cette \ue9tude a \ue9t\ue9 men\ue9e dans le but
de d\ue9terminer le type de l\u2019action g\ue9n\ue9tique
contr\uf4lant la mati\ue8re s\ue8che, ainsi que
d\u2019\ue9valuer l\u2019effet d\u2019interaction g\ue9notype x
environnement sur la mati\ue8re s\ue8che sur la patate douce. Cinq
diff\ue9rents parents en terme de mati\ue8re s\ue8che ont
\ue9t\ue9 crois\ue9s en moiti\ue9 diall\ue8le et dix familles
sont obtenues. Les semences sont plant\ue9es dans les boites en bois
dans les serres \ue0 Namulonge, Uganda. Dix g\ue9notypes pour
chacune des familles sont plant\ue9es dans l\u2019essai \ue0
Namulonge (environnement marrais et hautes terres) et Serere en bloques
compl\ue8tement randomis\ue9es, avec deux r\ue9p\ue9titions,
durant la p\ue9riode Octobre 2009-Mars 2010. Pour d\ue9terminer la
mati\ue8re s\ue8che, une quantit\ue9 de 200 g pour chacune des
g\ue9notypes a \ue9t\ue9 s\ue9ch\ue9e \ue0 650C
jusqu\u2019\ue0 ce que le poids soit constant. Les donn\ue9es sont
analys\ue9es en utilisant le logiciel Genstat. Aptitude
g\ue9n\ue9rale \ue0 la combinaison (AGC) et aptitude
sp\ue9cifique \ue0 la combinaison (ASC) sont calcul\ue9es selon
Mod\ue8le I, M\ue9thode 4 selon la description de Griffing (1956).
Hautes significative (P< 0,001) diff\ue9rences sont trouv\ue9es
aussi bien entre g\ue9notypes que familles pour la mati\ue8re
s\ue8che. Hautes significatives AGC (P<0,001) et ASC (P<0,01)
sont trouv\ue9es, signifiant que les diff\ue9rences observ\ue9es
entre les familles pour la mati\ue8re s\ue8che sont dues \ue0 la
fois \ue0 AGC et ASC. L\u2019importance relative de l\u2019AGC et
ASC \ue9tait 0,59, ce qui indique que l\u2019action
g\ue9n\ue9tique additive \ue9tait un peu plus importante que
l\u2019action g\ue9n\ue9tique non-additive en pr\ue9dicant la
performance des prog\ue9nitures pour la mati\ue8re s\ue8che.
L\u2019h\ue9ritabilit\ue9 en large sens (H) pour la mati\ue8re
s\ue8che \ue9tait de 0,70 et 0,73 en se basant respectivement sur
la moyenne du g\ue9notype et celle de la famille sur tous les
environnements, sugg\ue9rant que la mati\ue8re s\ue8che
\ue9tait mod\ue9r\ue9ment influenc\ue9e par
l\u2019environnement. Ceci indique que la s\ue9lection rapide des
g\ue9notypes serait possible, car les prog\ue9nitures peuvent
\ueatre pr\ue9venues en se basant sur le ph\ue9notype des
parents. Parent SPK (GCA=1,02) \ue9tait la meilleure combinant dans
cette \ue9tude. L\u2019effet des locations \ue9tait moins
significatif comparable aux saisons, sugg\ue9rant l\u2019importance
d\u2019\ue9valuer les g\ue9notypes sur plusieurs saisons, mais
dans les moins de locations dans le cadre d\u2019\ue9conomiser les
ressources
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
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