Improvement of common bacterial blight resistance in South African dry bean cultiver teebud

Common bacterial blight (CBB) caused by Xanthomonas axonopodis pv. phaseoli is an important seed-borne disease of dry beans in South Africa.  Development of resistant cultivars is considered the best control measurement for the disease. Backcross breeding was used to improve  BB resistance in the small white canning bean, cv. Teebus, using resistance sources XAN 159 and Wilk 2. High resistance levels in near-isogenic lines, developed in two independent breeding programmes, indicated successful  transfer of resistance from both sources. Presence of SCAR-markers, SU91 and BC420, in 35 of 39 XAN 159 derived Teebus lines and all lines derived from Wilk 2, confirmed successful resistance transfer. AFLP studies conducted to determine genetic relatedness of two near-isogenic Teebus lines, showed a similarity of 96.2% with the maximum similarity between  these lines and Teebus being 93.1%. One cultivar, Teebus-RCR2 with yield similar to Teebus and improved resistance to CBB has been released from the programme

Application of molecular markers in breeding for bean common blight resistance in South Africa

Sequence characterised amplified region (SCAR) markers, linked to four independent quantitative trait loci (QTL) in XAN 159 and GN #1 Nebr. sel. 27, are available for indirect selection of resistance to common bacterial blight in Phaseolus vulgaris . Existing SCAR-markers, SU91, BC420, BC409 and SAP6, were evaluated for potential use in the South Africa breeding programme. Segregating populations of progenies developed through backcross breeding with cultivars Teebus and Kranskop as susceptible recurrent parents, and XAN 159 and Vax 4 as resistant donor parents were evaluated for presence of existing markers. Presence of all four markers in improved Teebus lines (XAN 159 derived) confirmed transfer of resistance in these lines. Marker BC420 was absent in XAN 159 derived Kranskop-lines. These lines were only moderately resistant when tested in the greenhouse, indicating that the QTL linked to this marker is important in order to obtain high levels of resistance. Progenies from backcrosses with Kranskop as recurrent parent using Vax 4 have exhibited high levels of resistance and presence of all markers found in Vax 4 confirmed transfer of resistance. Marker-assisted selection can successfully be implemented in breeding for common bacterial blight resistance in South African materials.Les marqueurs de r\ue9gions amplifi\ue9es de s\ue9quences caract\ue9ris\ue9es (SCAR), associ\ue9es \ue0 quatre traits de loci quantitatives ind\ue9pendantes (QTL) dans XAN 159 et GN #1 Nebr. sel. 27, sont disponibles pour une s\ue9lection indirecte de r\ue9sistance au fl\ue9trissement commun dans Phaseolus vulgaris . Les marqueurs existants SCAR, SU91, BC420, BC409 et SAP6, \ue9taient \ue9valu\ue9s pour leur utilisation potentielle dans le programme d\u2019am\ue9lioration en Afrique du Sud. Les populations s\ue9gr\ue9gantes des prog\ue9nies d\ue9velopp\ue9es \ue0 travers l\u2019am\ue9lioration par croisement en retour avec les parents susceptibles recurrents et les parents donneurs r\ue9sistants XAN 159 et Vax 4 \ue9taient \ue9valu\ue9es pour la pr\ue9sence des marqueurs existants. La presence de tous les quatre marqueurs dans les lign\ue9es de Teebus am\ue9lior\ue9es (XAN 159) a confirm\ue9 le transfert de r\ue9sistance dans ces lign\ue9es. Le marqueur BC420 \ue9tait absent dans XAN 159 d\ue9riv\ue9 des lign\ue9es Kranskop. Ces lign\ue9es \ue9taient seulement mod\ue9r\ue9ment r\ue9sistantes lorsqu\u2019 elles \ue9taient test\ue9es en serre, indiquant l\u2019importance du QTL associ\ue9 \ue0 ce marqueur dans l\u2019obtention de niveaux \ue9lev\ue9s de r\ue9sistance. Les prog\ue9nies issues de croisements en retour avec Kranskop comme parent recurrant utilisant Vax 4 ont montr\ue9 des niveaux \ue9lev\ue9s de r\ue9sistance, et la pr\ue9sence de tous les marqueurs trouv\ue9s dans Vax 4 ont confirm\ue9 le transfert de r\ue9sistance. La s\ue9lection par marqueur asssist\ue9 peut \ueatre appliqu\ue9 avec succ\ue8s dans le programme d\u2019am\ue9lioration pour r\ue9sistance au fl\ue9trissement bact\ue9rien commun dans le mat\ue9riel Sud Africain

Pathogenic and genetic variation in Xanthomonas axonopodis pv. Phaseoli and its fuscans variant in Southern Africa

Common bacterial blight (CBB) caused by Xanthomonas axonopodis pv. phaseoli and its fuscans variant, X. axonopodis pv. phaseoli var. fuscans is a widespread disease of dry beans in South Africa. Variation within pathogen populations has been reported and in order to breed for resistance it is important to investigate whether variation exists within the local pathogen population. One hundred and forty three common bacterial blight isolates from 44 localities in four countries, were inoculated onto eight Phaseolus acutifolius lines that differentiate between pathogenic races. This differential set was expanded to include resistant genotypes, XAN 159, GN #1 Nebr. sel 27, Wilk 2, Wilk 6, Vax 4, Vax 5 and Vax 6 and cv. Teebus as susceptible check. Genetic variation within nine selected Xap and Xapf isolates and a non-pathogenic Xanthomonas isolate, was studied using RAPD and AFLP analysis. Genotypes XAN 159, Wilk 2, Wilk 6, Vax 4, Vax 5 and Vax 6 were resistant to all isolates, while GN #1 Nebr. sel 27 and cv. Teebus were susceptible. Isolates varied in aggressiveness on cv. Teebus; however, the pathogenic reaction on the set of differentials indicated that all, but one isolate, grouped in what has been reported as race 2. Thus, results based on reaction of the majority isolates, suggest the absence of different races. However, the distinct differential reaction recorded for a single isolate, may prove to represent another, as yet unrecorded, race of this pathogen. Both RAPD and AFLP analyses revealed high frequency of DNA polymorphism among isolates and could distinguish between Xap, Xapf and a non-pathogenic isolate. Differences between Xap and Xapf isolates demonstrate that these are two distinct groups of bacteria.Le fl\ue9trissement bact\ue9rien commun (CBB) caus\ue9 par Xanthomonas axonopodis pv. phaseoli et ses variantes \u201cfuscans\u201d, X. axonopodis var. pv. phaseoli est une maladie r\ue9pandue des haricots en Afrique du Sud. Pour am\ue9liorer la r\ue9sistance \ue0 la maladie, une \ue9tude \ue9tait men\ue9e pour \ue9valuer la variation \ue0 l\u2019int\ue9rieur de populations pathog\ue8nes locales. Pour ce faire, cent quarante trois isolats de bact\ue9ries communes de fl\ue9trissement issues de 144 localit\ue9s de quatre pays \ue9taient inocul\ue9s dans huit lign\ue9es de Phaseolus acutifolius diff\ue9rentes de races pathog\ue9niques. Cet ensemble differentiel \ue9tait \ue9tendu afin d\u2019inclure les g\ue9notypes r\ue9sistants XAN 159, GN #1 Nebr. sel 27, Wilk 2, Wilk 6, Vax 4, Vax 5 et Vax 6 ainsi que cv. Teebus comme t\ue9moins susceptible. La variation g\ue9n\ue9tique parmi neuf Xap et leurs isolats s\ue9lectionn\ue9s ainsi qu\u2019un isolat de Xanthomonas non-pathog\ue9nique \ue9taient \ue9tudi\ue9s par l\u2019analyse RAPD et AFLP. Les g\ue9notypes XAN 159, Wilk 2, Wilk 6, Vax 4, Vax 5 et Vax 6 \ue9taient r\ue9sistants \ue0 tous les isolats alors que GN #1 Nebr. sel 27 et cv. Teebus \ue9taient susceptibles. Les isolats variaient dans leur agressivit\ue9 au cv; par ailleurs, la r\ue9action pathog\ue9nique sur l\u2019ensemble des diff\ue9rentiels a indiqu\ue9 que tous les isolats sauf un seul, pouvaient \ueatre group\ue9s dans ce qui \ue9tait d\ue9crit comme race 2. Ainsi, les r\ue9sultats bas\ue9s sur la r\ue9action de la majorit\ue9 des isolats sugg\ue8rent l\u2019absence de diff\ue9rentes races. Par ailleurs, la r\ue9action diff\ue9rentielle distincte enregistr\ue9e dans un seul isolat, pourrait permettre de repr\ue9senter une autre race de ce pathog\ue8ne non encore enregistr\ue9e. Les analyses RAPD et AFLP ont r\ue9v\ue9l\ue9 une fr\ue9quence \ue9lev\ue9e du polymorphisme de l\u2019AND parmi les isolats et pourraient permettre de faire une distinction entre Xap, Xapf et un isolat non pathog\ue9nique. Les diff\ue9rences entre les isolats Xap et Xapf d\ue9montrent que ces derniers forment deux groupes distincts de bact\ue9ries

Stem rust resistance in South African wheat cultivars

The aim of this study was to attempt to identify reliable factors associated with dropout risk in a sample of 161 panic disorder patients treated with manualized cognitive behavior therapy. Four possible predictors of dropout were selected from the literature: level of education, treatment motivation, personality psychopathology, and initial symptom severity. Thirty-two patients (19.9%) were dropouts. Level of education and motivation were significantly associated with dropout, but the associations were small. Personality psychopathology and initial symptom severity were not associated with dropout. It is concluded that, at present, we are unable to make precise dropout risk predictions, even in a homogeneous group of patients treated using standardized treatment

Improvement of common bacterial blight resistance in South African dry bean cultivar teebus

Common bacterial blight (CBB) caused by Xanthomonas axonopodis pv. phaseoli is an important seed-borne disease of dry beans in South Africa. Development of resistant cultivars is considered the best control measurement for the disease. Backcross breeding was used to improve CBB resistance in the small white canning bean, cv. Teebus, using resistance sources XAN 159 and Wilk 2. High resistance levels in near-isogenic lines, developed in two independent breeding programmes, indicated successful transfer of resistance from both sources. Presence of SCAR-markers, SU91 and BC420, in 35 of 39 XAN 159 derived Teebus lines and all lines derived from Wilk 2, confirmed successful resistance transfer. AFLP studies conducted to determine genetic relatedness of two near-isogenic Teebus lines, showed a similarity of 96.2% with the maximum similarity between these lines and Teebus being 93.1%. One cultivar, Teebus-RCR2 with yield similar to Teebus and improved resistance to CBB has been released from the programme.Le fl\ue9trissement bact\ue9rien commun (CBB) caus\ue9 par Xanthomonas axonopodis pv. phaseoli est une importante maladie de grains des haricots secs en Afrique du Sud. Le d\ue9veloppement des cultivars r\ue9sistants est consid\ue9r\ue9 comme une meilleure mesure de contr\uf4le de la maladie. L\u2019am\ue9lioration par croisement en retour \ue9tait utilis\ue9e pour am\ue9liorer la r\ue9sistance au CBB dans le petit haricot blanc, cv.Teebus, en utilisant des sources r\ue9sistantes XAN 159 et Wilk 2. De niveaux \ue9lev\ue9s de r\ue9sistance dans des lign\ue9es proches isog\ue9niques, d\ue9velopp\ue9es dans deux programmes ind\ue9pendants d\u2019am\ue9lioration, ont indiqu\ue9 un transfert r\ue9ussi de r\ue9sistance de toutes ces deux sources. De la pr\ue9sence des marquers SCAR, SU91 et BC 420 dans 35 de 39 XAN 159 a d\ue9coul\ue9 les lign\ue9es Teebus et toutes les lign\ue9es d\ue9rivant de Wilk 2, confirmant ainsi un transfert r\ue9ussi de r\ue9sistance. Des \ue9tudes AFLP conduites pour d\ue9terminer la relation g\ue9n\ue9tique de deux lign\ue9es proches isog\ue9niques Teebus, ont montr\ue9 une similarit\ue9 de 96.2% avec la maximum de similarit\ue9 entre ces lign\ue9es et Teebus de 93.1%. Un cultivar, TeebusRCR2 avec rendement similaire au Teebus et r\ue9sistance am\ue9lior\ue9e au CBB a \ue9t\ue9 dissemin\ue9e par le programme

Evaluation of Selected Aspects of the Nutrition Therapeutic Programme Offered to HIV-Positive Women of Child-Bearing Age in Western Cape Province, South Africa

Background: The Nutrition Therapeutic Programme (NTP) involves the provision of food supplements at primary health clinics (PHCs) to correct nutritional deficiencies in vulnerable groups. Although previous studies have identified problems with implementing the programme at PHCs, assessments of its efficiency have been scarce.Objective: To evaluate implementation of the NTP at PHCs that provide antiretroviral therapy.Methods: A cross-sectional, descriptive study was conducted at 17 PHCs located within 3 districts of Western Cape Province. Two target groups were chosen: 32 staff members working at the sites and 21 women of child-bearing age enrolled in the NTP. Questionnaires were used to obtain data.Results: Only 2 women (10%) lived in food-secure households; the rest were either at risk of hunger (29%) or classified as hungry (61%). Most of the women knew they had to take the supplements to improve their nutritional status, but the majority only recalled receiving basic nutritional advice, and the information was mainly given verbally. Ten of the women had shared their supplements with others, mostly with their children. The study identified lack of clearly defined NTP responsibilities at the PHCs, causing confusion amongst the staff. Although many staff members expressed problems with the NTP, only 38% of them reported having routine evaluations regarding the programme.Conclusion: Several aspects compromised the effectiveness of the NTP, including socioeconomic factors leading to clients’ non-compliance. The strategic organisation and implementation of the NTP varied between different PHCs offering antiretroviral therapy, and staff experienced difficulties with the logistics of the programme

Identification and mapping of AFLP markers linked to peanut (Arachis hypogaea L.) resistance to the aphid vector of groundnut rosette disease

Groundnut rosette disease is the most destructive viral disease of peanut in Africa and can cause serious yield losses under favourable conditions. The development of disease-resistant cultivars is the most effective control strategy. Resistance to the aphid vector, Aphis craccivora, was identified in the breeding line ICG 12991 and is controlled by a single recessive gene. Bulked segregant analysis (BSA) and amplified fragment length polymorphism (AFLP) analysis were employed to identify DNA markers linked to aphid resistance and for the development of a partial genetic linkage map. A F2:3 population was developed from a cross using the aphid-resistant parent ICG 12991. Genotyping was carried out in the F2 generation and phenotyping in the F3 generation. Results were used to assign individual F2 lines as homozygous-resistant, homozygous-susceptible or segregating. A total of 308 AFLP (20 EcoRI+3/MseI+3, 144 MluI+3/MseI+3 and 144 PstI+3/MseI+3) primer combinations were used to identify markers associated with aphid resistance in the F2:3 population. Twenty putative markers were identified, of which 12 mapped to five linkage groups covering a map distance of 139.4 cM. A single recessive gene was mapped on linkage group 1, 3.9 cM from a marker originating from the susceptible parent, that explained 76.1% of the phenotypic variation for aphid resistance. This study represents the first report on the identification of molecular markers closely linked to aphid resistance to groundnut rosette disease and the construction of the first partial genetic linkage map for cultivated peanu

Local scale patterns of gene flow and genetic diversity in a crop–wild–weedy complex of sorghum (Sorghum bicolor (L.) Moench) under traditional agricultural field conditions in Kenya

Little information is available on the extent and patterns of gene flow and genetic diversity between cultivated sorghum and its wild related taxa under local agricultural conditions in Africa. As well as expanding knowledge on the evolutionary and domestication processes for sorghum, such information also has importance in biosafety, conservation and breeding programmes. Here, we examined the magnitude and dynamics of crop–wild gene flow and genetic variability in a crop–wild–weedy complex of sorghum under traditional farming in Meru South district, Kenya. We genotyped 110 cultivated sorghum, and 373 wild sorghum individuals using a panel of ten polymorphic microsatellite loci. We combined traditional measures of genetic diversity and differentiation with admixture analysis, population assignment, and analyses of spatial genetic structure to assess the extent and patterns of gene flow and diversity between cultivated and wild sorghum. Our results indicate that gene flow is asymmetric with higher rates from crop to wild forms than vice versa. Surprisingly, our data suggests that the two congeners have retained substantial genetic distinctness in the face of gene flow. Nevertheless, we found no significant differences in genetic diversity measures between them. Our study also did not find evidence of isolation by distance in cultivated or wild sorghum, which suggests that gene dispersal in the two conspecifics is not limited by geographic distance. Overall our study highlights likely escape and dispersal of transgenes within the sorghum crop–wild–weedy complex if genetically engineered varieties were to be introduced in Africa’s traditional farming system

A QTL study on late leaf spot and rust revealed one major QTL for molecular breeding for rust resistance in groundnut (Arachis hypogaea L.)

Late leaf spot (LLS) and rust are two major foliar diseases of groundnut (Arachis hypogaea L.) that often occur together leading to 50–70% yield loss in the crop. A total of 268 recombinant inbred lines of a mapping population TAG 24 × GPBD 4 segregating for LLS and rust were used to undertake quantitative trait locus (QTL) analysis. Phenotyping of the population was carried out under artificial disease epiphytotics. Positive correlations between different stages, high to very high heritability and independent nature of inheritance between both the diseases were observed. Parental genotypes were screened with 1,089 simple sequence repeat (SSR) markers, of which 67 (6.15%) were found polymorphic. Segregation data obtained for these markers facilitated development of partial linkage map (14 linkage groups) with 56 SSR loci. Composite interval mapping (CIM) undertaken on genotyping and phenotyping data yielded 11 QTLs for LLS (explaining 1.70–6.50% phenotypic variation) in three environments and 12 QTLs for rust (explaining 1.70–55.20% phenotypic variation). Interestingly a major QTL associated with rust (QTLrust01), contributing 6.90–55.20% variation, was identified by both CIM and single marker analysis (SMA). A candidate SSR marker (IPAHM 103) linked with this QTL was validated using a wide range of resistant/susceptible breeding lines as well as progeny lines of another mapping population (TG 26 × GPBD 4). Therefore, this marker should be useful for introgressing the major QTL for rust in desired lines/varieties of groundnut through marker-assisted backcrossing