Field evaluation of selected cassava genotypes for cassava brown streak disease based on symptom expression and virus load

Background Production of cassava (Manihot esculenta Crantz), a food security crop in sub-Saharan Africa, is threatened by the spread of cassava brown streak disease (CBSD) which manifests in part as a corky necrosis in the storage root. It is caused by either of two virus species, Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), resulting in up to 100% yield loss in susceptible varieties. Methods This study characterized the response of 11 cassava varieties according to CBSD symptom expression and relative CBSV and UCBSV load in a field trial in Uganda. Relative viral load was measured using quantitative RT-PCR using COX as an internal housekeeping gene. Results A complex situation was revealed with indications of different resistance mechanisms that restrict virus accumulation and symptom expression. Four response categories were defined. Symptom expression was not always positively correlated with virus load. Substantially different levels of the virus species were found in many genotypes suggesting either resistance to one virus species or the other, or some form of interaction, antagonism or competition between virus species. Conclusions A substantial amount of research still needs to be undertaken to fully understand the mechanism and genetic bases of resistance. This information will be useful in informing breeding strategies and restricting virus spread.Background Production of cassava (Manihot esculenta Crantz), a food security crop in sub-Saharan Africa, is threatened by the spread of cassava brown streak disease (CBSD) which manifests in part as a corky necrosis in the storage root. It is caused by either of two virus species, Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), resulting in up to 100% yield loss in susceptible varieties. Methods This study characterized the response of 11 cassava varieties according to CBSD symptom expression and relative CBSV and UCBSV load in a field trial in Uganda. Relative viral load was measured using quantitative RT-PCR using COX as an internal housekeeping gene. Results A complex situation was revealed with indications of different resistance mechanisms that restrict virus accumulation and symptom expression. Four response categories were defined. Symptom expression was not always positively correlated with virus load. Substantially different levels of the virus species were found in many genotypes suggesting either resistance to one virus species or the other, or some form of interaction, antagonism or competition between virus species. Conclusions A substantial amount of research still needs to be undertaken to fully understand the mechanism and genetic bases of resistance. This information will be useful in informing breeding strategies and restricting virus spread.Background Production of cassava (Manihot esculenta Crantz), a food security crop in sub-Saharan Africa, is threatened by the spread of cassava brown streak disease (CBSD) which manifests in part as a corky necrosis in the storage root. It is caused by either of two virus species, Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), resulting in up to 100% yield loss in susceptible varieties. Methods This study characterized the response of 11 cassava varieties according to CBSD symptom expression and relative CBSV and UCBSV load in a field trial in Uganda. Relative viral load was measured using quantitative RT-PCR using COX as an internal housekeeping gene. Results A complex situation was revealed with indications of different resistance mechanisms that restrict virus accumulation and symptom expression. Four response categories were defined. Symptom expression was not always positively correlated with virus load. Substantially different levels of the virus species were found in many genotypes suggesting either resistance to one virus species or the other, or some form of interaction, antagonism or competition between virus species. Conclusions A substantial amount of research still needs to be undertaken to fully understand the mechanism and genetic bases of resistance. This information will be useful in informing breeding strategies and restricting virus spread.Background Production of cassava (Manihot esculenta Crantz), a food security crop in sub-Saharan Africa, is threatened by the spread of cassava brown streak disease (CBSD) which manifests in part as a corky necrosis in the storage root. It is caused by either of two virus species, Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), resulting in up to 100% yield loss in susceptible varieties. Methods This study characterized the response of 11 cassava varieties according to CBSD symptom expression and relative CBSV and UCBSV load in a field trial in Uganda. Relative viral load was measured using quantitative RT-PCR using COX as an internal housekeeping gene. Results A complex situation was revealed with indications of different resistance mechanisms that restrict virus accumulation and symptom expression. Four response categories were defined. Symptom expression was not always positively correlated with virus load. Substantially different levels of the virus species were found in many genotypes suggesting either resistance to one virus species or the other, or some form of interaction, antagonism or competition between virus species. Conclusions A substantial amount of research still needs to be undertaken to fully understand the mechanism and genetic bases of resistance. This information will be useful in informing breeding strategies and restricting virus spread

Morphotypes, distribution and uses of false banana in Uganda

Enset ( Ensete ventricosum ) is commonly known as the \u201cfalse banana\u201d because of its close resemblance to the domesticated banana ( Musa spp.) plant. It is Ethiopia\u2019s most important traditional staple crop in the densely populated south and south-western parts of the country; where it is grown and exploited for its starch to make various food and industrial products. In Uganda, little is known about enset regarding its ethno-botany and distribution, yet it occurs in the country. The objective of this study was to map out the distribution and document the ethno-botany and uses of enset in Uganda. A survey was carried out throughout the country to identify its natural habitats in different regions. Local people were interviewed on the uses of enset, etymology, and identification of different morphotypes. Morphological descriptors and sex of enset accessions were used in classification or identification of morphotypes. Enset was generally widely, but sparsely distributed in the different regions in Uganda; growing at elevations ranging between 988 (Moyo district) to 2,150 (Kapchorwa district) metres above sea level (masl) and in a variety of habitats. Out of the 80 districts of Uganda (as of 2009), enset was reported and observed in 30 districts. Thirteen local names of enset and their meanings were documented; but it was widely referred to as Kitembe. Different plant parts were used for medicinal purposes; while the leaves were used in local beer brewing. There were five enset morphotypes distinguished by morphological traits, such as plant height (short vs tall), mid-rib colour (light green vs pink), pseudostem background appearance (light green vs brown), leaf margin colour, male bud colour, and leaf length-breadth ratio. A detailed molecular level genetic diversity assessment is recommended for further validation of the morphotypes.Le Bananier d\u2019Abyssinie ( Ensete ventricosum ) est commun\ue9ment appel\ue9 comme \uab\ua0fausse banane\ua0\ubb \ue0 cause de sa tr\ue8s grande ressemblance au plant de banane ( Musa spp) domestiqu\ue9. C\u2019est un aliment de base traditionnel tr\ue8s important dans les r\ue9gions de grande densit\ue9 de population du Sud et Sud-Ouest d\u2019Ethiopie\ua0; o\uf9 il est cultiv\ue9 et exploit\ue9 pour son amidon utilis\ue9 pour divers produits alimentaires et industriels. En Ouganda, tr\ue8s peu d\u2019informations relatives \ue0 son ethnobotanique et \ue0 sa distribution sont disponibles sur Bananier d\u2019Abyssinie, pourtant il est pr\ue9sent dans le pays. L\u2019objective de cette \ue9tude \ue9tait de cartographier la distribution et de documenter l\u2019ethnobotanique et les usages du bananier d\u2019Abyssinie en Ouganda. Une enqu\ueate a \ue9t\ue9 conduite \ue0 travers le pays pour identifier ses habitats naturels dans diff\ue9rentes r\ue9gions. Les populations locales ont \ue9t\ue9 interview\ue9es sur les usages du bananier d\u2019Abyssinie, l\u2019\ue9tymologie, et l\u2019identification des diff\ue9rents morphotypes. Les descripteurs morphologiques et le sexe des accessions du bananier d\u2019Abyssinie ont \ue9t\ue9 utilis\ue9s dans la classification ou l\u2019identification des morphotypes. Le bananier d\u2019Abyssinie a \ue9t\ue9 largement, but sporadiquement distribu\ue9 dans les diff\ue9rentes r\ue9gions en Ouganda\ua0; les altitudes de cultures varient entre 988 (district de Moyo) \ue0 2150 m\ue8tres (district de Kapchorwa) au-dessus du niveau de la mer (masl) et dans une vari\ue9t\ue9 d\u2019habitats. Sur les 80 districts (comme en 2009), le bananier d\u2019Abyssinie a \ue9t\ue9 rapport\ue9 et observ\ue9 dans 30 districts. Les treize noms locaux du bananier d\u2019Abyssinie et leurs significations ont \ue9t\ue9 document\ue9s\ua0; mais il a \ue9t\ue9 largement r\ue9f\ue9r\ue9 au Kitembe. Les diff\ue9rentes parties du plant ont \ue9t\ue9 utilis\ue9es \ue0 des fins m\ue9dicinales, alors que les feuilles ont \ue9t\ue9 utilis\ue9es dans la pr\ue9paration de la bi\ue8re locale. Il y avait cinq morphotypes du bananier d\u2019Abyssinie distingu\ue9s par des traits morphologiques, tels que la hauteur du plant (courte vs haute), couleur de mid-nervure (vert-clair vs rose), fond d\u2019apparence de pseudo tige (vert-clair vs marron), couleur de la marge de la feuille, m\ue2le mais la couleur, et un ratio longueur/largeur de la feuille. Une \ue9valuation d\ue9taill\ue9e de la diversit\ue9 g\ue9n\ue9tique mol\ue9culaire est recommand\ue9e pour davantage validation des morphotypes

Identification of F1 cassava (Manihot esculenta Crantz) progeny using microsatellite markers and capillary electrophoresis

Generation of genetic diversity is necessary in improving on the potential of cassava when faced with various biotic and abiotic challenges. Presently, cassava breeders are breeding for a number of traits, such as drought tolerance, early root bulking, yield, starch, beta-carotene, protein, dry matter, pest and disease resistance, by relying on genetic diversity that exists in manihot esculenta germplasm. Controlled pollination is one of the main methods used to generate genetic diversity in cassava. However, the process of controlled pollination especially in an open field is prone to contamination by illegitimate pollen right from the time of pollination, seed collection, nursery bed establishment to planting of the trials. Therefore, authentication of the progeny obtained from cas-sava crosses is very important for genetic studies. Twelve informative microsatellite markers were used to verify the authenticity of 364 F1 progeny thought to come from four controlled parental crosses. The transmission of each allele at nine microsatellite loci was tracked from parents to progeny in each of the four Namikonga-derived F1 cassava families. Out of the 364 F1 progeny, 317 (87.1%) were true-to-type, 44 (12.1%) were a product of self-pollination and 3 (0.8%) were a product of open pollination. The consistency of the results obtained using microsatellite markers makes this technique a reliable tool for assessing the purity of progeny generated from cassava crosses

Effect of self-pollination with heat-treated pollen on parthenocarpy and homozygosity in cassava

Cassava\u2019s ( Manihot esculenta Crantz) high heterozygosity complicates its genetic improvement via selective breeding. Double haploid (DH) technology can be used to improve the crop\u2019s heterozygosity, thereby improving the capacity for genetic improvement. The objective of this study was to evaluate the effect of self-pollination using heated pollen on pollen tube penetration, fruit set, seed and haploid embryo development in cassava genotypes for the production of haploid cassava. Pollen from two cassava genotypes, NASE3 and NASE14, was heated at 40, 50 and 60 oC for 0.5, 1.0 and 2.0 hr each. The heated pollen was used in six rounds of self-pollinations. Pollen tube penetration was monitored by fluorescent microscopy, followed by early embryo rescue and ovule culture. Ploidy and zygosity were assessed using flow cytometry and single-nucleotide polymorphism analysis, respectively. Pollen germinated on the stigma, grew within the style through the nucellar beak, but did not reach the embryo sac, thus achieving no fertilisation in all the 5756 self-pollinated flowers. There was a reduction in pollen germination (in vitro and in vivo), pollen tube penetration and fruit set with increasing temperature. Heat-treated pollen stimulated division of the egg cell and induced development of parthenocarpic fruits. Up to 6 embryoids per ovule were observed and all regenerated plantlets were diploid, with up to 93.0% increased homozygosity. For the first time, plant regeneration from ovules, pollinated with fresh pollen at 14 days after pollination, was achieved indicating improved speed in plant regeneration. The data generated are important for the development of protocols for cassava DH plant production.La forte h\ue9t\ue9rozygotie du manioc ( Manihot esculenta Crantz) complique son am\ue9lioration g\ue9n\ue9tique par s\ue9lection s\ue9lective. La technologie d\u2018 haplo\uefde double (DH) peut \ueatre utilis\ue9e pour am\ue9liorer l\u2019h\ue9t\ue9rozygotie de la culture, am\ue9liorant ainsi la capacit\ue9 d\u2019am\ue9lioration g\ue9n\ue9tique. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer l\u2019effet de l\u2019auto-pollinisation \ue0 l\u2019aide de pollen chauff\ue9 sur la p\ue9n\ue9tration du tube pollinique, la nouaison, le d\ue9veloppement des graines et des embryons haplo\uefdes dans les g\ue9notypes de manioc pour la production de manioc haplo\uefde. Le pollen de deux g\ue9notypes de manioc, NASE3 et NASE14, a \ue9t\ue9 chauff\ue9 \ue0 40, 50 et 60 oC pendant 0,5, 1,0 et 2,0 heure (s) chacun. Le pollen chauff\ue9 a \ue9t\ue9 utilis\ue9 dans six cycles d\u2019auto-pollinisation. La p\ue9n\ue9tration du tube pollinique a \ue9t\ue9 surveill\ue9e par microscopie fluorescente, suivie d\u2019un sauvetage pr\ue9coce des embryons et d\u2019une culture d\u2019ovules. La plo\uefdie et la zygosit\ue9 ont \ue9t\ue9 \ue9valu\ue9es \ue0 l\u2019aide de la cytom\ue9trie en flux et de l\u2019analyse du polymorphisme mononucl\ue9otidique, respectivement. Le pollen a germ\ue9 sur le stigmate, s\u2019est d\ue9velopp\ue9 dans le style \ue0 travers le bec nucellaire, mais n\u2019a pas atteint le sac embryonnaire, n\u2019obtenant ainsi aucune f\ue9condation dans toutes les 5756 fleurs autogames. Il y avait une r\ue9duction de la germination du pollen (in vitro et in vivo), de la p\ue9n\ue9tration du tube pollinique et de la nouaison avec l\u2019augmentation de la temp\ue9rature. Le pollen trait\ue9 thermiquement a stimul\ue9 la division de l\u2019ovule et induit le d\ue9veloppement de fruits parth\ue9nocarpiques. Les 6 embryo\uefdes par ovule ont \ue9t\ue9 observ\ue9s et toutes les plantules r\ue9g\ue9n\ue9r\ue9es \ue9taient diplo\uefdes, avec 93,0% d\u2018augmentation d\u2019homozygotie. Pour la premi\ue8re fois, la r\ue9g\ue9n\ue9ration des plantes \ue0 partir des ovules, pollinis\ue9es avec du pollen frais 14 jours apr\ue8s la pollinisation, a \ue9t\ue9 r\ue9alis\ue9e, indiquant une vitesse am\ue9lior\ue9e de r\ue9g\ue9n\ue9ration des plantes. Les donn\ue9es g\ue9n\ue9r\ue9es sont importantes pour l\u2019\ue9laboration de protocoles de production de plantes de manioc de DH

Fruit set and plant regeneration in cassava following interspecific pollination with castor bean

The increasing demand for cassava ( Manihot esculenta Crantz) for food and non-food uses in the tropics necessitates that its breeding for increased root productivity be made faster. The characteristic long breeding cycle and heterozygous nature of this crop, pose a major obstacle to its rapid genetic improvement. This study aimed at inter-pollinating cassava with castor bean ( Ricinus communis ), with a purpose of inducing and regenerating cassava doubled haploids (DHs). A total of 3,349 flowers from twelve elite cassava varieties were inter-pollinated with caster bean. A total of 803 fruits were harvested for early embryo rescue and/or ovule culture. Of these, three were dissected to obtain seven unique embryos, while 800 were dissected to obtain 1312 young ovules, all of which were cultured in vitro. Overall, 82 (6.25%) of the cultured ovules formed callus that originated from the embryosac region, which is haploid. Four out of seven rescued embryos (57.1%) regenerated into plantlets. Ploidy analyses of 24 samples using flow cytometry revealed that 23 of the analysed samples were diploid. However, one callus sample was anueploid. Only one sample had an exceptionally high level of homozygosity ( 84.2%). These findings lay a foundation for future research aimed at induction of haploids in cassava.La demande croissante de manioc (\ua0 Manihot esculenta \ua0Crantz\ua0) \ue0 usage alimentaire et non alimentaire dans les tropiques\ua0n\ue9cessite que sa reproduction pour une productivit\ue9 accrue des racines soit faite plus rapidement.\ua0Le long cycle de reproduction et le caract\ue8re h\ue9t\ue9rozygote de cette plante constituent un obstacle majeur dans la rapidit\ue9 de son am\ue9lioration g\ue9n\ue9tique.\ua0Cette \ue9tude visait \ue0 inter-polliniser le manioc avec le haricot (\ua0 Ricinus communis \ua0), dans le but d\u2019induire et de r\ue9g\ue9n\ue9rer le manioc d\u2019haplo\uefdes doubl\ue9 (HD).\ua0Un total de 3 349 fleurs de douze \ue9lites vari\ue9t\ue9s de manioc ont \ue9t\ue9 inter-pollinis\ue9es avec le haricot.\ua0Un total de 803 fruits ont \ue9t\ue9 r\ue9colt\ue9s pour les embryons pr\ue9matur\ue9s qui etaient sauves et\ua0/ ou la\ua0culture d\u2019ovules\ua0.\ua0Parmi ceux-ci,\ua0trois ont \ue9t\ue9 diss\ue9qu\ue9s pour obtenir sept embryons uniques\ua0,\ua0tandis que 800 ont \ue9t\ue9 diss\ue9qu\ue9s pour obtenir 1312 jeunes ovules, qui ont tous \ue9t\ue9 cultiv\ue9s\ua0in vitro\ua0.\ua0Un total de 82 (6,25%) des ovules en culture ont form\ue9 des cals provenant de la\ua0r\ue9gion\ua0embryonnaire\ua0, qui est haplo\uefde. Quatre parmi sept embryons sauv\ue9s (57,1%) se sont r\ue9g\ue9n\ue9r\ue9s en plantules.\ua0Les analyses de plo\uefdie de 24 \ue9chantillons par cytom\ue9trie en flux ont r\ue9v\ue9l\ue9 que 23 des \ue9chantillons analys\ue9s \ue9taient diplo\uefdes.Cependant, un \ue9chantillon de cals \ue9tait anueplo\uefde.\ua0Un seul \ue9chantillon pr\ue9sentait un niveau d\u2019homozygotie exceptionnellement \ue9lev\ue9\ua0(84,2\ua0%).\ua0Ces r\ue9sultats sont les bases des recherches dans le futur sur la cause des haplo\uefdes dans le manioc

In vitro embryo rescue and plant regeneration following self-pollination with irradiated pollen in cassava (Manihot esculenta Crantz)

Cassava is a highly heterozygous species; hence, current methods used in classical cassava breedingcannot match the urgent need to high yielding varieties. Recently, progress was made through androgenesis and gynogenesis as pathways for raising doubled cassava haploid lines to overcome problems associated with cassava’s inherent reproductive biology, but these efforts were limited (nocandidate cassava plantlets were regenerated). For the first time, this study shows that pollen irradiation coupled with self-pollination and embryo rescue regenerated 62 candidate cassava plantlets. Plants of an elite cassava variety, Nase14, served as a mother plant and as the pollen donor for the irradiation. Irradiation dosages of 50 to 250 Gray studied across five pollination events and 300 or 500 Gray in one pollination event caused a reduction in pollen germination up to 67.0%. By 15 days after pollination (DAP) with irradiated pollen, up to 89.7% of the pollinated flowers had aborted. By embryo rescue time (42 DAP), significant differences were observed in number of fruits, seeds and embryos generated, with the non-irradiated pollen treatments having significantly higher numbers. Sixteen (16) heterozygous SSR markers in the parent and ploidy analysis showed that none of the regenerated plants was haploid or homozygous. However, the plantlets resulting from pollination with non-irradiated pollen had 56.2% homozygous loci, while progeny derived from irradiated treatments had frequencies of homozygous loci between 28.1 and 55.0%. This is the first time to use irradiated pollen in cassava as a pathway to generate candidate plantlets as an initial step in double haploid production.Key words: Cassava, doubled haploids, embryo rescue, plant regeneration, pollen germination, pollenirradiation

Oesophageal cancer management guidelines for Uganda

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Adverse Childhood Experiences and Adult Cardiometabolic Risk Factors and Disease Outcomes: Cross-Sectional, Populationbased Study of Adults in Rural Uganda

Background: Cardiovascular diseases (CVD) pose a major threat to public health in sub-Saharan African communities, where the burden of these classes of illnesses is expected to double by 2030. Growing research suggests that past developmental experiences and early life conditions may also elevate CVD risk throughout the life course. Greater childhood stress and adversity are consistently associated with a range of adult CVDs and associated risk factors, yet little research exists on the long-term effects of early life stress on adult physical health outcomes, especially CVD risk, in sub-Saharan African contexts. This study aims to evaluate the associations between adverse childhood experiences and adult cardiometabolic risk factors and health outcomes in a population-based study of adults living in Mbarara, a rural region of southwestern Uganda. Methods Data come from an ongoing, whole-population social network cohort study of adults living in the eight villages of Nyakabare Parish, Mbarara. A modified version of the Adverse Childhood Experiences-International Questionnaire (ACEs) assessed past exposure to physical, emotional, and sexual adversity. Participants also took part in a health fair where medical histories on cardiometabolic risk factors and cardiovascular diseases were gathered. Multiple logistic regression models estimated the associations between ACEs and cardiometabolic risk factors and health outcomes. Results Data were available on 545 adults. The average number of ACEs was 4.9 out of a possible 16. The cumulative number of ACEs were associated with having a history of heart attack and/or heart failure (adjusted odds ratio (AOR) = 1.11, 95% confidence interval (CI) = 0.999-1.234, P = 0.051), but the estimated association was not statistically significant. ACEs did not have statistically significant associations with any others measures of adult cardiometabolic risk and CVD. Conclusions: Adverse childhood experiences are not associated with a range of adult cardiometabolic risk factors and health outcomes in this sample of rural Ugandan adults. Further research in this sample is necessary to identify the pathways that may motivate these null relationship and possibly protect against adverse cardiometabolic and cardiovascular health outcomes

Alternative splicing and differential subcellular localization of the rat FGF antisense gene product

<p>Abstract</p> <p>Background</p> <p>GFG/NUDT is a nudix hydrolase originally identified as the product of the fibroblast growth factor-2 antisense (FGF-AS) gene. While the FGF-AS RNA has been implicated as an antisense regulator of FGF-2 expression, the expression and function of the encoded GFG protein is largely unknown. Alternative splicing of the primary FGF-AS mRNA transcript predicts multiple GFG isoforms in many species including rat. In the present study we focused on elucidating the expression and subcellular distribution of alternatively spliced rat GFG isoforms.</p> <p>Results</p> <p>RT-PCR and immunohistochemistry revealed tissue-specific GFG mRNA isoform expression and subcellular distribution of GFG immunoreactivity in cytoplasm and nuclei of a wide range of normal rat tissues. FGF-2 and GFG immunoreactivity were co-localized in some, but not all, tissues examined. Computational analysis identified a mitochondrial targeting sequence (MTS) in the N-terminus of three previously described rGFG isoforms. Confocal laser scanning microscopy and subcellular fractionation analysis revealed that all rGFG isoforms bearing the MTS were specifically targeted to mitochondria whereas isoforms and deletion mutants lacking the MTS were localized in the cytoplasm and nucleus. Mutation and deletion analysis confirmed that the predicted MTS was necessary and sufficient for mitochondrial compartmentalization.</p> <p>Conclusion</p> <p>Previous findings strongly support a role for the FGF antisense RNA as a regulator of FGF2 expression. The present study demonstrates that the antisense RNA itself is translated, and that protein isoforms resulting form alternative RNA splicing are sorted to different subcellular compartments. FGF-2 and its antisense protein are co-expressed in many tissues and in some cases in the same cells. The strong conservation of sequence and genomic organization across animal species suggests important functional significance to the physical association of these transcript pairs.</p