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

Population diversity of rice bacterial leaf blight isolates in Uganda

The deployment of resistant cultivars is the best option to control bacterial leaf blight (BLB) and requires an understanding of the pathogen diversity. BLB caused by Xanthomonas oryzae pv.oryzae is a destructive disease of rice (Oryza sativa L.) in Uganda. Unfortunately, detailed information on Ugandan pathogen populations is not available. A set of 21 differential rice genotypes that have known resistance genes were used in a split plot design to test for differential virulence of six different isolates of X.oryzae pv.oryzae obtained from seed samples collected from Eastern Uganda. Statistical analysis showed diversity among isolates. The susceptibility of the differentials with two to four-gene combinations and the resistance of IR24 to Ugandan isolates were unusual and, therefore suggested a different pattern between Asian and Ugandan isolates at pathological level. Although the isolates were fewer in number, attempts to classify them into pathogenic races gave rise to 6 different races, as each isolate caused a particular virulence pattern on the differentials. The six races formed two significantly different (p ≤ 0.05) groups of one race (UX041) and five races (UX051, UX00, UX050, UX058 and UX044). These races would be used in screening rice germplasm available and/or newly introduced to Uganda

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 ≤ Xanthomonas oryzae pv. oryzae isolate (UX00) and lesion lengths were scored 21 days after inoculation (DAI). Griffing’s 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 flétrissement bactérien des feuilles du riz ( Xanthomonas oryzae ) constitue une contrainte majeur à la production du riz ( Oryza sativa L.) en Uganda. L’évaluation de la résistance des cultivars communément utilisés s’avère nécessaire comme une des strategies de développement des cultivars résistants. Des cultivars de riz (Oryza sativa L.) dont trois résistants et trois susceptibles étaient croisés en dispositif diallèle complet pour produire des générations F1 et F2 dans une serre de l’ Institut National de Recherche sur les Resources Végétales (NaCRRI) à Namulonge en Ouganda. Les parents et les populations F2 étaient soumis à l’isolat UX00 du Xanthomonas oryzae pv.oryzae et les longueurs de la lésion étaient évaluées 21 jours après l’inoculation. L’analyse de l’aptitude à la combinaison par la méthode de Griffing ont révélé des effets significatifs de l’Aptitude Spécifique à la Combinaison (ASC) et non significatifs de l’Aptitude Générale à la Combinaison (AGC), indiquant la prépondérance des effets génétiques non additifs dans le contrôle de la résistance au flétrissement bactérien des feuilles (FBF). Des génotypes NERICA14, NERICA10 et NERICA4 avaient des valeurs souhaitables d’AGC, et étaient ainsi des meilleurs combinants pour la résistance au FBF. Des hybrides CO39 x NERICA10 et NERICA14 x IRAT104 avaient des valeurs favorables d’ASC. Ils sont donc promettant dans le développement des descendants résistants au FBF. Des effets réciproques significatifs indiquent l’importance de la contribution maternelle dans le contrôle de la virulence du FBF. Pour ce faire, des lignées résistantes peuvent être utilisées comme parents femelles de peur d’affecter le transfert de la résistance aux descendants, et les hybrids ainsi que leur réciproques pourraient être manipulés séparément. De faibles valeurs (0.9%) du coefficient génétique de détermination au sens restreint et valeurs moyennes (16.4%) du coefficient génétique de détermination au sens large accentuent l’influence de l’action génétique non additive dans le contrôle de la résistance au FBF, ce qui confirme une sélection effective des meilleurs génotypes aux générations avancées quand le maximum d’homozygotie est fixé

Using research to prepare for outbreaks of severe acute respiratory infection

Severe acute respiratory infections (SARI) remain one of the leading causes of mortality around the world in all age groups. There is large global variation in epidemiology, clinical management and outcomes, including mortality. We performed a short period observational data collection in critical care units distributed globally during regional peak SARI seasons from 1 January 2016 until 31 August 2017, using standardised data collection tools. Data were collected for 1 week on all admitted patients who met the inclusion criteria for SARI, with follow-up to hospital discharge. Proportions of patients across regions were compared for microbiology, management strategies and outcomes. Regions were divided geographically and economically according to World Bank definitions. Data were collected for 682 patients from 95 hospitals and 23 countries. The overall mortality was 9.5%. Of the patients, 21.7% were children, with case fatality proportions of 1% for those less than 5 years. The highest mortality was in those above 60 years, at 18.6%. Case fatality varied by region: East Asia and Pacific 10.2% (21 of 206), Sub-Saharan Africa 4.3% (8 of 188), South Asia 0% (0 of 35), North America 13.6% (25 of 184), and Europe and Central Asia 14.3% (9 of 63). Mortality in low-income and low-middle-income countries combined was 4% as compared with 14% in high-income countries. Organ dysfunction scores calculated on presentation in 560 patients where full data were available revealed Sequential Organ Failure Assessment (SOFA) scores on presentation were significantly associated with mortality and hospital length of stay. Patients in East Asia and Pacific (48%) and North America (24%) had the highest SOFA scores of >12. Multivariable analysis demonstrated that initial SOFA score and age were independent predictors of hospital survival. There was variability across regions and income groupings for the critical care management and outcomes of SARI. Intensive care unit-specific factors, geography and management features were less reliable than baseline severity for predicting ultimate outcome. These findings may help in planning future outbreak severity assessments, but more globally representative data are required

Using research to prepare for outbreaks of severe acute respiratory infection

Abstract Severe acute respiratory infections (SARI) remain one of the leading causes of mortality around the world in all age groups. There is large global variation in epidemiology, clinical management and outcomes, including mortality. We performed a short period observational data collection in critical care units distributed globally during regional peak SARI seasons from 1 January 2016 until 31 August 2017, using standardised data collection tools. Data were collected for 1 week on all admitted patients who met the inclusion criteria for SARI, with follow-up to hospital discharge. Proportions of patients across regions were compared for microbiology, management strategies and outcomes. Regions were divided geographically and economically according to World Bank definitions. Data were collected for 682 patients from 95 hospitals and 23 countries. The overall mortality was 9.5%. Of the patients, 21.7% were children, with case fatality proportions of 1% for those less than 5 years. The highest mortality was in those above 60 years, at 18.6%. Case fatality varied by region: East Asia and Pacific 10.2% (21 of 206), Sub-Saharan Africa 4.3% (8 of 188), South Asia 0% (0 of 35), North America 13.6% (25 of 184), and Europe and Central Asia 14.3% (9 of 63). Mortality in low-income and low-middle-income countries combined was 4% as compared with 14% in high-income countries. Organ dysfunction scores calculated on presentation in 560 patients where full data were available revealed Sequential Organ Failure Assessment (SOFA) scores on presentation were significantly associated with mortality and hospital length of stay. Patients in East Asia and Pacific (48%) and North America (24%) had the highest SOFA scores of >12. Multivariable analysis demonstrated that initial SOFA score and age were independent predictors of hospital survival. There was variability across regions and income groupings for the critical care management and outcomes of SARI. Intensive care unit-specific factors, geography and management features were less reliable than baseline severity for predicting ultimate outcome. These findings may help in planning future outbreak severity assessments, but more globally representative data are required