Genetic diversity among tropical provitamin a maize inbred lines and implications for a biofortification program

Insights into the diversity and relationships among elite breeding materials are an important component in maize improvement programs. We genotyped 63 inbred lines bred for high levels of provitamin A using 137 single nucleotide polymorphism markers. A total of 272 alleles were detected with gene diversity of 0.36. Average genetic distance was 0.36 with 56% of the pairs of lines having between 0.30 and 0.40. Eighty-six percent of the pairs of lines showed relative kinship values <0.50, which indicated that the majority of these provitamin A inbred lines were unique. Relationship pattern and population structure analysis revealed presence of seven major groups with good agreement with Neighbour Joining clustering and somewhat correlated with pedigree and breeding origin. Utilization of this set of provitamin A lines in a new biofortification program will be aided by information from both molecular-based grouping and pedigree analysis. The results should guide breeders in selecting parents for hybrid formation and testing as a short-term objective, and parents with diverse alleles for new breeding starts as a long-term objective in a provitamin A breeding program

Characterization of elite maize inbred lines for drought tolerance using Simple Sequence Repeats markers

The development of drought tolerant maize has been limited by the suggested complexity of the environment on drought phenotypic traits. However, some simple sequence repeats (SSRs) molecular markers linked to drought tolerance via quantitative trait loci (QTL) have been identified in maize but their use requires validation on newly developed elite maize inbred lines. This study therefore aims to validate 19 selected SSR markers linked to maize drought tolerance and determine the genetic diversity of sixty-eight elite maize inbred lines. Genomic DNA was extracted with a CTAB method and the PCR products were separated on agarose gel with auto radiograms visually scored for polymorphic bands to establish a data matrix. Assessment of the genetic links among the inbred lines was carried out using cluster analysis. The 68 maize inbred lines were clustered based on a matrix of genetic similarity Jaccard using the UPGMA algorithm. Some of the markers that were informative included P-bnlg238, Phi037, P-bnlg1179 and Umc2214 and these showed significant group differentiation among the inbred lines. Marker Umc1447, Umc1432 and Umc2359 were among the markers with monomorphic bands, while Phi034, Bnlg1074 and P-umc1542 showed no characterized bands. The polymorphism information content (PIC) value of the informative markers ranged from 0.13 (Bnlg434) to 0.76 (P-bnlg238). The cluster analysis classified the maize inbred lines into four groups based on the SSR data. The exploitation of information of genetic diversity among the inbred maize lines to develop drought tolerant hybrids is hereby discussed

Determination of the heterotic groups of maize inbred lines and the inheritance of their resistance to the maize weevil

Maize weevil ( Sitophilus zeamais Motschulsky) is a major maize ( Zea mays L) storage insect pest in the tropics. Fifty-two inbred lines developed for weevil resistance were crossed to two testers, A and B, to determine their heterotic groups and inheritance of resistance to maize weevil. For 10 testcrosses selected for performance by tester, the correspondent testcrosses onto the opposite tester and all the parents involved in those crosses, were included in the combining study. Of 52 inbred lines, 7 had significantly positive general combining ability (GCA) for yield, with a maximum GCA effect of 1.24t.ha-1. Based on the specific combining ability (SCA) effect, 23 inbred lines were assigned to heterotic Group A, 24 to Group B, and 5 to both A and B. The combining ability test for weevil resistance revealed that only one inbred, WL118-9, was classified as moderately resistant with a susceptibility index (SI=5.4), two lines were moderately susceptible; and the remaining inbreds were susceptible to highly susceptible to the maize weevil. Additive and non-additive gene action were important for yield, but for weevil resistance, additive gene action was more important. Weevil resistance exists and is moderately heritable.Le charan\ue7on du ma\uefs ( Sitophilus zeamais Motschulsky) est un plus grand ravageur du ma\uefs ( Zea mays L) dans les tropiques. Cinquante-deux lign\ue9es d\ue9velopp\ue9es pour la r\ue9sistance au charan\ue7on du ma\uefs \ue9taient crois\ue9es aux testeurs A et B afin de d\ue9terminer leurs groupes h\ue9t\ue9rotiques ainsi que la transmission de la r\ue9sistance au charan\ue7on du ma\uefs. Pour dix lign\ue9es s\ue9lectionn\ue9es pour test de performance par le testeur, les croisements correspondants au testeur oppos\ue9 ainsi que tous les parents impliqu\ue9s dans le croisement \ue9taient inclus dans l\u2019 \ue9tude d\u2019aptitude. Parmi les 52 lign\ue9es, 7 avaient significativement montr\ue9 une positive Aptitude G\ue9n\ue9rale \ue0 la combinaison (GCA) pour le rendement, avec un effet maximum GCA de 1.24 t ha-1. Bas\ue9 sur l\u2019 Aptitude Sp\ue9cifique \ue0 la Combinaison (SCA), 23 lign\ue9es ont \ue9t\ue9 attribu\ue9es au groupe h\ue9t\ue9rotique A, 24 au groupe B et 5 aux deux groupes h\ue9t\ue9rotiques A et B. Le test d\u2019aptitude \ue0 la r\ue9sistance au charan\ue7on a r\ue9v\ue9l\ue9e q\u2019une seule lign\ue9e, WL118-9 \ue9tait classifi\ue9e comme mod\ue9r\ue9ment r\ue9sistante avec un index de susceptibilit\ue9 de 5.4, deux lign\ue9es \ue9taient mod\ue9r\ue9ment susceptibles tandis que les lign\ue9es restantes \ue9taient soit susceptibles ou hautement susceptibles au charan\ue7on du ma\uefs. L\u2019action additive et non additive des g\ue8nes \ue9taient tr\ue8s importante. Les g\ue8nes de r\ue9sistance au charan\ue7on du ma\uefs existent et sont mod\ue9r\ue9ment transmissibles \ue0 la descendance

APPLICATION OF MORPHO-ANATOMICAL TRAITS OF MAIZE PLANT TO QUALITY CONTROL AND QUALITY ASSURANCE IN MAIZE SEED SYSTEM

Good seed quality can be obtained through control of the entire seed production process. There are emerging issues in the seed sector due to seed quality in market. In many countries seed and planting materials available to farmers are often of insufficient quality, thus undermining the potential performance of crops. The objective this study was to use morpho-anatomical traits to determine the levels of maize hybrid seed purity on the market in Uganda. A total of 120 samples of four popular commercial maize hybrid were collected from agro-dealers in 13 districts, representing 3 seed companies\u2019 distribution network. The samples were planted and evaluated based on their descriptors, using an Alpha Lattice Design, with two replications at the National Crops Resources Research Institute (NaCRRI), Namulonge. Data were collected for 33 morpho-anatomical traits. Results showed significant (P&lt;0.05) differences within hybrids, and sources of seed among districts. Among the test materials, only Longe 9H had no significant (P&lt;0.05) difference within traits but others had some levels of significant (P&lt;0.05) differences. The principal component analysis of quantitative traits resulted in four components for each variety, with the explanation total of 53.3% for Longe 6H, 51.1% for Longe 7H, and 92.8% for Longe 9H and 39.1% for Longe 10%. There were varying levels of contamination of commercial hybrids based on morphoanatomical traits diversity within hybrids, compared to their descriptors for the traits evaluated. Hence, there is need to strengthen the quality control sub-sector for improved productivity at farmer levels.Des semences de bonne qualit\ue9 peuvent \ueatre obtenues en exer\ue7ant un control syst\ue9matique sur chacun des maillons du syst\ue8me de production semenci\ue8re. Le secteur semencier conna\ueet de plus en plus de difficult\ue9s, et ceci en raison de la qualit\ue9 des semences sur le march\ue9. Dans plusieurs pays, les semences disponibles pour les producteurs sont souvent de qualit\ue9 non satisfaisante, reduisant ainsi la performance des cultures. L\u2019objectif de l\u2019\ue9tude \ue9tait de se servir des caract\ue8res morpho-anatomiques afin de determiner le niveau purit\ue9 des semences de ma\uefs hybride sur le march\ue9 semencier en Ouganda. Au total 120 \ue9chantillons des quatre vari\ue9t\ue9es commerciales populaires de ma\uefs hybride ont \ue9t\ue9 collect\ue9s chez les distributeurs de semences dans 13 districts, repr\ue9sentant les r\ue9seaux de distribution de 3 compagnies semenci\ue8res. Les \ue9chantillons ont \ue9t\ue9 sem\ue9s et \ue9valu\ue9s en se basant sur leurs descripteurs. Le dispositive exp\ue9rimental Alpha Lattice a \ue9t\ue9 utilis\ue9, avec deux r\ue9p\ue9titions \ue0 l\u2019institut national de recherche des ressources culturales (NaCRRI), Namulonge. Les donn\ue9es de 33 caract\ue8res morphoanatomiques ont \ue9t\ue9 collect\ue9es. Les r\ue9sultats ont montr\ue9 des differences significatives (P&lt;0,05) ont \ue9t\ue9 observ\ue9es parmi les hybrides, ainsi que les sources des semences au sein des districts. Parmi les mat\ue9riels test\ue9s, seul Longe 9H n\u2019avait exhib\ue9 aucune difference significative (P&lt;0,05) des caract\ue8res \ue9valu\ue9s, mais certains ont des differences significatives \ue0 (P&lt;0,05). l\u2019analyse en composntes principales des traits quantitatifs a montr\ue9 quatre composantes pour chaque vari\ue9t\ue9, avec l\u2019ensemble de ces composantes expliquant 53,3% de la variation totale pour Longe 6H, 51,1% pour Longe 7H, 92,8% pour Longe 9H et 39,1% pour Longe 10%. Les niveaux de contamination \ue9taient variables, sugg\ue9rant la n\ue9cessit\ue9 de renforcer le sous-secteur de control de qualit\ue9 en vue d\u2019une meilleure productivit\ue9 au niveau des producteurs

Reaction of rice cultivars to a virulent rice yellow mottle virus strain in Uganda

Rice ( Oryza spp.) has long been an important food staple for many traditional rice growing communities. Key developments in efforts to improve rice production such as the development of NERICA varieties have been widely recognised. Nonetheless, emerging diseases such as the Rice Yellow Mottle Virus sobemovirus (RYMV) undermine dissemination of new technologies and sustained productivity of the crop. The RYMV is highly variable and several resistance-breaking strains have been identified. Appropriate sources of resistance to RYMV should be identified and characterised in order to pyramid genes for both complete and partial resistance. In this study, reaction of nine (9) rice cultivars to RYMV virulent strain in Uganda was determined. Four upland and three lowland NERICA varieties, an O. Sativa lowland variety, Gigante and IR64 were observed. Isolates of RYMV were collected from three "hot-spots" in Uganda (Lira, Luweero and Iganga). The isolate from Iganga was most virulent on RYMV susceptible cultivar (IR64), and thus used to constitute study treatment evaluated in the study. Cultivars were potted and raised in a screenhouse experiment arranged in a randomised complete block design (RCBD) with three replicates. Significant differences for relative area under disease progress curve (RAUDPC) (P 640.01) were detected among the cultivars. Similarly, significant positive correlations (P 640.05) were observed between mean disease score and percentage reduction in grain weight and between percentage grain weight and reduction in plant height. Susceptible cultivars were characterised based on premature death, and significantly reduced grain weight and plant height (P 640.01 and P 640.05), respectively. These results demonstrated the aggressive nature of the specific RYMV strain, and provided evidence with regard to the importance of grain weight and plant height in evaluating RYMV disease resistance.Le riz ( Oryza spp.) a \ue9t\ue9 depuis longtemps un aliment de base pour plusieurs communaut\ue9s cultivatrices de riz. Les d\ue9veloppements-cl\ue9s dans l\u2019effort d\u2019am\ue9liorer la production rizicole, tel que le d\ue9veloppement des vari\ue9t\ue9s NERICA, ont \ue9t\ue9 largement reconnus. N\ue9anmoins, l\u2019apparition des maladies telle que le virus de la panachure jaune de type sobemovirus contraint la diss\ue9mination des nouvelles technologies et la productivit\ue9 soutenue de la culture. Le virus de la panachure jaune du riz est tr\ue8s variable et plusieurs souches virulentes ont \ue9t\ue9 identifi\ue9es. De sources appropri\ue9es de r\ue9sistance \ue0 la maladie de la panichure jaune du riz devront \ueatre identifi\ue9es et caract\ue9ris\ue9es afin de pyramider les g\ue8nes pour une r\ue9sistance complete et/ou partielle. Dans cette \ue9tude, la r\ue9action de 9 cultivars de riz au virus virulent de la panachure jaune en Ouganda \ue9tait d\ue9termin\ue9e. Quatre vari\ue9t\ue9s NERICA de montagne et trois vari\ue9t\ue9s NERICA des bas-fonds, ainsi qu\u2019une vari\ue9t\ue9 des bas-fonds de type O. sativa, Gigante et IR64, \ue9taient observ\ue9es. Les isolats du virus de la panachure jaune du riz \ue9taient collect\ue9s des \u201czones dangereuses\u201d de l\u2019Ouganda, notamment Lira, Luwero et Iganga. L\u2019isolat de l\u2019Iganga \ue9tait le plus virulent au cultivar IR64 susceptible au virus de la panachure jaune et donc \ue9tait utilis\ue9 pour constituer le traitement \ue9valu\ue9 dans cette \ue9tude. Les cultivars \ue9taient cultiv\ue9s en pots dans une serre et arranges en blocs al\ue9atoires complets avec trois r\ue9p\ue9titions. Des diff\ue9rences significatives pour la surface relative sous la courbe progressive de la maladie (P 640.01) \ue9taient d\ue9tect\ue9es parmi les cultivars. De fa\ue7on similaire, des corr\ue9lations positives significatives (P 640.05) \ue9taient observ\ue9es entre les moyennes des cotations de la maladie et le pourcentage de r\ue9duction du poids des grains, et entre le pourcentage du poids des grains et la r\ue9duction de la hauteur de plant. Les cultivars susceptibles \ue9taient caract\ue9ris\ue9s sur base de la mort pr\ue9matur\ue9e, et la r\ue9duction significative du poids des grains et la hauteur de plant (P 640.01 et P 640.05), respectivement. Ces r\ue9sultats ont d\ue9montr\ue9 la nature aggressive du virus de la panachure jaune et fournissent l\u2019 \ue9vidence de l\u2019omportance du poids en grains et la hauteur de plants dans l\u2019\ue9valuation de la r\ue9sistance \ue0 la maladie de la panachure jaune du riz

Extracellular Hsp72 concentration relates to a minimum endogenous criteria during acute exercise-heat exposure

Extracellular heat-shock protein 72 (eHsp72) concentration increases during exercise-heat stress when conditions elicit physiological strain. Differences in severity of environmental and exercise stimuli have elicited varied response to stress. The present study aimed to quantify the extent of increased eHsp72 with increased exogenous heat stress, and determine related endogenous markers of strain in an exercise-heat model. Ten males cycled for 90 min at 50% O2peak in three conditions (TEMP, 20°C/63% RH; HOT, 30.2°C/51%RH; VHOT, 40.0°C/37%RH). Plasma was analysed for eHsp72 pre, immediately post and 24-h post each trial utilising a commercially available ELISA. Increased eHsp72 concentration was observed post VHOT trial (+172.4%) (P<0.05), but not TEMP (-1.9%) or HOT (+25.7%) conditions. eHsp72 returned to baseline values within 24hrs in all conditions. Changes were observed in rectal temperature (Trec), rate of Trec increase, area under the curve for Trec of 38.5°C and 39.0°C, duration Trec ≥ 38.5°C and ≥ 39.0°C, and change in muscle temperature, between VHOT, and TEMP and HOT, but not between TEMP and HOT. Each condition also elicited significantly increasing physiological strain, described by sweat rate, heart rate, physiological strain index, rating of perceived exertion and thermal sensation. Stepwise multiple regression reported rate of Trec increase and change in Trec to be predictors of increased eHsp72 concentration. Data suggests eHsp72 concentration increases once systemic temperature and sympathetic activity exceeds a minimum endogenous criteria elicited during VHOT conditions and is likely to be modulated by large, rapid changes in core temperature

A mouse model for triple-negative breast cancer tumor-initiating cells (TNBC-TICs) exhibits similar aggressive phenotype to the human disease

<p>Abstract</p> <p>Background</p> <p>Triple-negative breast cancer (TNBC) exhibit characteristics quite distinct from other kinds of breast cancer, presenting as an aggressive disease--recurring and metastasizing more often than other kinds of breast cancer, without tumor-specific treatment options and accounts for 15% of all types of breast cancer with higher percentages in premenopausal African-American and Hispanic women. The reason for this aggressive phenotype is currently the focus of intensive research. However, progress is hampered by the lack of suitable TNBC cell model systems.</p> <p>Methods</p> <p>To understand the mechanistic basis for the aggressiveness of TNBC, we produced a stable TNBC cell line by sorting for 4T1 cells that do not express the estrogen receptor (ER), progesterone receptor (PgR) or the gene for human epidermal growth factor receptor 2 (HER2). As a control, we produced a stable triple-positive breast cancer (TPBC) cell line by transfecting 4T1 cells with rat HER2, ER and PgR genes and sorted for cells with high expression of ER and PgR by flow cytometry and high expression of the HER2 gene by Western blot analysis.</p> <p>Results</p> <p>We isolated tumor-initiating cells (TICs) by sorting for CD24⁺/CD44^high/ALDH1⁺cells from TNBC (TNBC-TICs) and TPBC (TPBC-TICs) stable cell lines. Limiting dilution transplantation experiments revealed that CD24⁺/CD44^high/ALDH1⁺cells derived from TNBC (TNBC-TICs) and TPBC (TPBC-TICs) were significantly more effective at repopulating the mammary glands of naïve female BALB/c mice than CD24^-/CD44^-/ALDH1^-cells. Implantation of the TNBC-TICs resulted in significantly larger tumors, which metastasized to the lungs to a significantly greater extent than TNBC, TPBC-TICs, TPBC or parental 4T1 cells. We further demonstrated that the increased aggressiveness of TNBC-TICs correlates with the presence of high levels of mouse twenty-five kDa heat shock protein (Hsp25/mouse HspB1) and seventy-two kDa heat shock protein (Hsp72/HspA1A).</p> <p>Conclusions</p> <p>Taken together, we have developed a TNBC-TICs model system based on the 4T1 cells which is a very useful metastasis model with the advantage of being able to be transplanted into immune competent recipients. Our data demonstrates that the TNBC-TICs model system could be a useful tool for studies on the pathogenesis and therapeutic treatment for TNBC.</p

Genetic analysis of resistance to rice bacterial blight in Uganda

Rice bacterial blight ( Xanthomonas oryzae pv. oryzae ) is a major constraint to rice ( Oryza sativa L.) production in Uganda and as part of strategies to develop resistant cultivars, it is important to evaluate resistance of commonly used cultivars. A full-diallel mating design involving three resistant and three susceptible rice cultivars was used to produce F1 and F2 progenies in a screen-house at the National Crop Resources Research Institute (NaCRRI), Namulonge in Uganda. The parents and F2 populations were challenged with the 64 Xanthomonas oryzae pv. oryzae isolate (UX00) and lesion lengths were scored 21 days after inoculation (DAI). Griffing\u2019s combining ability analysis showed significant specific combining ability (SCA) and non-significant general combining ability (GCA) effects, indicating the preponderance of non-additive gene effects in controlling the resistance to bacterial leaf blight (BLB) in rice. Rice genotypes, NERICA14, NERICA10 and NERICA4 had desirable GCA estimates, and were, therefore, the best general combiners. Crosses CO39 x NERICA10 and NERICA14 x IRAT104 had favorable SCA values. These hybrids are thus, promising in developing the BLB resistant progenies. Significant reciprocal effects indicate the importance of maternal contribution in controlling the BLB virulence. For this, resistant lines can be used as female parents for fear of affecting transfer of resistance to the progenies, and the hybrids and their reciprocals would be handled separately. Low estimates of narrow sense coefficient of genetic determination (NSCGD) (0.9%) and medium broad sense coefficient of genetic determination (BSCGD) estimates (16.4%) highlight the influence of non-additive gene action in controlling the resistance to BLB, confirming an effective selection of superior genotypes at advanced generations when the maximum homozygosity is fixed.Le fl\ue9trissement bact\ue9rien des feuilles du riz ( Xanthomonas oryzae ) constitue une contrainte majeur \ue0 la production du riz ( Oryza sativa L.) en Uganda. L\u2019\ue9valuation de la r\ue9sistance des cultivars commun\ue9ment utilis\ue9s s\u2019av\ue8re n\ue9cessaire comme une des strategies de d\ue9veloppement des cultivars r\ue9sistants. Des cultivars de riz (Oryza sativa L.) dont trois r\ue9sistants et trois susceptibles \ue9taient crois\ue9s en dispositif diall\ue8le complet pour produire des g\ue9n\ue9rations F1 et F2 dans une serre de l\u2019 Institut National de Recherche sur les Resources V\ue9g\ue9tales (NaCRRI) \ue0 Namulonge en Ouganda. Les parents et les populations F2 \ue9taient soumis \ue0 l\u2019isolat UX00 du Xanthomonas oryzae pv.oryzae et les longueurs de la l\ue9sion \ue9taient \ue9valu\ue9es 21 jours apr\ue8s l\u2019inoculation. L\u2019analyse de l\u2019aptitude \ue0 la combinaison par la m\ue9thode de Griffing ont r\ue9v\ue9l\ue9 des effets significatifs de l\u2019Aptitude Sp\ue9cifique \ue0 la Combinaison (ASC) et non significatifs de l\u2019Aptitude G\ue9n\ue9rale \ue0 la Combinaison (AGC), indiquant la pr\ue9pond\ue9rance des effets g\ue9n\ue9tiques non additifs dans le contr\uf4le de la r\ue9sistance au fl\ue9trissement bact\ue9rien des feuilles (FBF). Des g\ue9notypes NERICA14, NERICA10 et NERICA4 avaient des valeurs souhaitables d\u2019AGC, et \ue9taient ainsi des meilleurs combinants pour la r\ue9sistance au FBF. Des hybrides CO39 x NERICA10 et NERICA14 x IRAT104 avaient des valeurs favorables d\u2019ASC. Ils sont donc promettant dans le d\ue9veloppement des descendants r\ue9sistants au FBF. Des effets r\ue9ciproques significatifs indiquent l\u2019importance de la contribution maternelle dans le contr\uf4le de la virulence du FBF. Pour ce faire, des lign\ue9es r\ue9sistantes peuvent \ueatre utilis\ue9es comme parents femelles de peur d\u2019affecter le transfert de la r\ue9sistance aux descendants, et les hybrids ainsi que leur r\ue9ciproques pourraient \ueatre manipul\ue9s s\ue9par\ue9ment. De faibles valeurs (0.9%) du coefficient g\ue9n\ue9tique de d\ue9termination au sens restreint et valeurs moyennes (16.4%) du coefficient g\ue9n\ue9tique de d\ue9termination au sens large accentuent l\u2019influence de l\u2019action g\ue9n\ue9tique non additive dans le contr\uf4le de la r\ue9sistance au FBF, ce qui confirme une s\ue9lection effective des meilleurs g\ue9notypes aux g\ue9n\ue9rations avanc\ue9es quand le maximum d\u2019homozygotie est fix\ue9