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Singh, R.P.

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Singh
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Singh, R.P.

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  • Maladies et ravageurs du ble: guide d'identification au champ
    (CIMMYT, 1987) Prescott, J.M.; Abeyo Bekele Geleta; Bowman, J.; Burnett, P.A.; De Milliano, W.A.J.; Ransom, J.K.; Saari, E.E.; Singh, R.P.
    Depourvus de chlorophylle, ce en quoi ils different des autres plantes, les champignons n'ont done pas de capacite de photosyntese. Au lieu d'elaborer leur propre nourriture, ils absorbent des elements nutritifs qu'ils puisent dans les tissus marts ou vivants de l'hote. Ils se propagent de diverses manieres et peuvent etre transmis par la graine ou le sol, ou disperses par le vent, l'eau (de pluie ou d'arrosage), les insectes, les animaux et l'homme. L'infection par les champignons pathogenes est liee a divers facteurs: en general, leur reproduction requiert la presence d'eau a la surface de l'h6te et depend a la fois de la sensibilite de ce dernier, de la densite d'inoculum et de la temperature ambiante, et d'autres facteurs du milieu. Si certains champignons ne s'attaquent qu'a une ou a quelques especes hotes, d'autres par contre s'attaquent indistinctement a plusieurs d'entre elles. Les sympt6mes et l'evolution de la maladie dependent egalement de l'interaction entre le parasite et l'hote. Selan la nature des champignons qui sont a l'origine de la maladie, les symptomes peuvent etre semblables ou differents, ainsi leur identification categorique devra etre basee sur leur morphologie. Sauf indication contraire, les champignons dont ii sera traits ici sont ceux qui attaquent le ble tendre, le ble dur et le triticale.
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  • Morpho-physiological traits associated with cold stress tolerance in tropical maize (Zea mays L.)
    (Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2010) Zaidi, P.; Yadav, M.; Maniselvan, P.; Khan, R.; Shadakshari, T.V.; Singh, R.P.; Pal, D.
    Winter season maize (Zea mays L.) has emerged a new crop in many parts of South and Southeast Asia, where the crop has to face low temperature regimes (<5°C) for few weeks during vegetative growth stage. The objective of this study was to identify the morphological and physiological traits associated with cold stress tolerance during vegetative growth period, when maximum dry matter is accumulated and floral primodia are formed. A total of 80 cultivars, including hybrids and open pollinated varieties (OPVs) from International Maize and Wheat Improvement Center (CIMMYT) and Indian maize program were evaluated in replicated trials at Indian Agricultural Research Institute (IARI), New Delhi and at Regional Research Station, Haryana Agriculture University, Karnal, India during the winter season, where critical period of vegetative growth and floral primodia developmental stage was exposed to <10°C temperature. Data on various growth and developmental traits and key physiological traits were recorded during the low temperature regime. Except ears per plant and physiological maturity, the cold stress significantly affected all the growth and developmental traits and also physiological traits studied. However, significant genotypic variability was observed for most of the traits studied. Genotypes with relatively high leaf appearance and extension rate, less cold injury symptoms and cell membrane damage showed good level of cold tolerance in terms of reproductive behavior and eventually grain yield under cold stress. These secondary traits could be used in selection index along with days to anthesis, anthesis-silking interval (ASI) and grain yield for selection and improvement of tropical maize for low temperature adaptation.
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  • Genetic analysis of water-logging tolerance in tropical maize (Zea Mays L.)
    (Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2010) Zaidi, P.; Maniselvan, P.; Srivastava, Ashish; Yadav, P.; Singh, R.P.
    Approximately 80% of maize (Zea mays L.) in South and Southeast Asia is grown as a rain-fed crop, where temporary excessive soil moisture or water-logging during the summer-rainy season is one of the major production constraints in large areas of this region. The present genetic study analyzed the tolerance of tropical maize to water-logging stress. Elite maize inbred lines with known stable performance in terms of improved grain yield under water-logging stress were crossed using half-diallel (7 x 7) and line × tester (8 × 3) mating designs, in which four lines were common in both the mating designs. F1 progenies (excluding reciprocals) and their parents were evaluated under managed water-logging stress at knee high stage (V7-8 growth stage) at the maize research farm, Indian Agricultural Research Institute, New Delhi, India (28.4°N, 77.1°E, 228.1 masl). In addition, the same set of entries was simultaneously evaluated under a normal moisture regime. Analysis showed that both general combining ability (GCA) and specific combining ability (SCA) effects were statistically significant. However, the GCA effect was comparatively higher (P<0.01) than the SCA effect (P<0.05). This result suggests that both additive and non-additive factors affect the expression of tolerance to water-logging stress in tropical maize. Analysis of the diallel and L × T dataset showed that water-logging tolerance in maize followed an additive-dominance genetic model, with additive gene effects dominating. Our findings suggest that reciprocal recurrent selection would be an effective approach for improving water-logging tolerance in tropical maize. Evaluating S1 progeny per se and their test-crosses under managed water-logging stress, discarding susceptible fraction and combining the selected best lines in terms of per se and test-cross performance could result in improved water-logging tolerant population. The new lines derived from the improved population could be used in developing water-logging tolerant synthetic varieties to exploit the additive gene effects and hybrids to exploit the non-additive gene action.
    Publication
  • Stability in performance of quality protein maize under abiotic stress
    (Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2008) Zaidi, P.; Vasal, S.K.; Maniselvan, P.; Jha, G.C.; Mehrajjudin; Singh, R.P.
    Quality protein maize (QPM) has emerged an affordable and viable option to alleviate protein malnutrition and reduce animal feed costs, given that its grain protein contains more than double the lysine and tryptophan concentrations of normal endosperm maize. For commercial success, QPM cultivars must be competitive with normal maize in productivity and should show stable performance across environments, especially with respect to yield and protein quality traits. In the tropics, drought and low-nitrogen (N) fertility are major constraints to maize productivity. In this study, we analyze the stability of performance of CIMMYT tropical and subtropical elite QPM hybrids across stressed (drought and low N) and unstressed environments. In general, stress significantly affected all agronomic traits except male flowering. The effect was comparatively large under drought stress. Among the quality traits, grain protein, tryptophan, and lysine contents showed significant variation across environments. There was an increase in grain protein (12.7%) and in lysine (10.3%) and tryptophan contents (8.1%) under drought stress, while levels of these grain quality traits were reduced under low N by 17.0, 12.5, and 15.6%, respectively. However, the effect of stressed environments was comparatively small on protein quality traits, including tryptophan and lysine content in protein. The variation in protein quality across environments was statistically significant but largely due to genotypic variability. Variation due to environment and genotype by environment (G x E) interaction was statistically non-significant for protein quality traits, except in the case of lysine content in protein, where G x E was significant. Our results suggest that grain yield and grain protein content are the most unstable traits, whereas tryptophan followed by lysine content are the most stable, across stressed and unstressed environments.
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  • Relationship between drought and excess moisture tolerance in maize (Zea mays L.)
    (Southern Cross Publishing Group, 2008) Zaidi, P.; Yadav, M.; Singh, D.; Singh, R.P.
    Maize crops grown during summer-rainy season in Asian tropics are prone to face both drought and excess moisture stress due uneven distribution patterns of monsoon rains in the region. We attempted to identify the relationship between drought and excess moisture tolerance through evaluation of a set of elite maize inbred lines, including lines with known performance under drought, excess moisture and normal inbred lines with unknown performance under either of the stresses. Under normal moisture, performance of normal lines was slightly better than drought and excess moisture lines. However, under stress condition performance of normal lines was very poor with average yield 9.1% under drought and 18.7% under excess moisture stress in comparison to normal moisture. On the other hand, drought lines yielded up to 61.8% under drought and 52.1% under excess moisture in comparison to their yields under normal moisture. Performance of excess moisture lines was also good across stress environments with average yield 68.2% under excess moisture and 35.6% under drought. Relationship between yields under drought and excess moisture stress was strong and significant with drought lines (R2 = 0.587**), but it was relatively weak with excess moisture lines (R2 = 0.288*), while the relationship highly weak with normal lines (R2 = 0.043ns). Our results suggest that improved performance of drought tolerant lines across environments might be related to constitutive changes in stress-adaptive secondary traits such as - anthesis-silking interval <5.0 days, reduced barrenness, delayed senescence and minimum loss of leaf chlorophyll under stress conditions. These constitutive changes with selection and improvement for flowering stage drought tolerance might resulted in improved performance of genotypes under both drought and excess moisture stress, without any yield penalty under normal moisture.
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  • Identification and mapping of leaf, stem and stripe rust resistance quantitative trait loci and their interactions in durum wheat
    (Springer Verlag, 2012) Singh, A.K.; Pandey, M.P.; Singh, A.K.; Knox, R.; Ammar, K.; Clarke, J.M.; Clarke, F.R.; Singh, R.P.; Pozniak, C.; DePauw, R.M.; McCallum, B.D.; Cuthbert, R.; Randhawa, H.S.; Fetch, T.
    Leaf rust (Puccinia triticina Eriks.), stripe rust (Puccinia striiformis f. tritici Eriks.) and stem rust (Puccinia graminis f. sp. tritici) cause major production losses in durum wheat (Triticum turgidum L. var. durum). The objective of this research was to identify and map leaf, stripe and stem rust resistance loci from the French cultivar Sachem and Canadian cultivar Strongfield. A doubled haploid population from Sachem/Strongfield and parents were phenotyped for seedling reaction to leaf rust races BBG/BN and BBG/BP and adult plant response was determined in three field rust nurseries near El Batan, Obregon and Toluca, Mexico. Stripe rust response was recorded in 2009 and 2011 nurseries near Toluca and near Njoro, Kenya in 2010. Response to stem rust was recorded in field nurseries near Njoro, Kenya, in 2010 and 2011. Sachem was resistant to leaf, stripe and stem rust. A major leaf rust quantitative trait locus (QTL) was identified on chromosome 7B at Xgwm146 in Sachem. In the same region on 7B, a stripe rust QTL was identified in Strongfield. Leaf and stripe rust QTL around DArT marker wPt3451 were identified on chromosome 1B. On chromosome 2B, a significant leaf rust QTL was detected conferred by Strongfield, and at the same QTL, a Yr gene derived from Sachem conferred resistance. Significant stem rust resistance QTL were detected on chromosome 4B. Consistent interactions among loci for resistance to each rust type across nurseries were detected, especially for leaf rust QTL on 7B. Sachem and Strongfield offer useful sources of rust resistance genes for durum rust breeding.
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  • Breeding for enhanced zinc and iron concentration in CIMMYT spring wheat germplasm
    (Czech Academy of Agricultural Sciences, 2011) Velu, G.; Singh, R.P.; Huerta-Espino, J.; Peña, Roberto; Ortiz-Monasterio, I.
    Micronutrient malnutrition, resulting from dietary deficiency of important minerals such as zinc (Zn) and iron (Fe), is a widespread food-related health problem. Genetic enhancement of crops with elevated levels of these micronutrients is one of the most cost effective ways of solving global micronutrient malnutrition problem. Development and dissemination of high Zn and Fe containing high-yielding, disease-resistant wheat varieties by International Maize and Wheat Improvement Center (CIMMYT) is initially targeted for the Indo-Gangetic plains of South Asia, a region with high population density and high micronutrient malnutrition. The most promising sources for grain Zn and Fe concentrations are wild relatives, primitive wheats and landraces. Synthetic hexaploids were developed at CIMMYT by crossing Aegilops taushii and high Zn and Fe containing accessions of T. dicoccon. Current breeding efforts at CIMMYT have focused on transferring genes governing increased Zn and Fe from T. spelta, T. dicoccon based synthetics, land races and other reported high Zn and Fe sources to high yielding elite wheat backgrounds.
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  • Evaluation of CIMMYT germplasm for resistance to leaf spotting diseases of wheat
    (Czech Academy of Agricultural Sciences, 2011) Singh, P.K.; Duveiller, E.; Singh, R.P.
    The leaf spotting disease complex is a major biotic constrain in enhancing grain production in the major wheat growing regions. Two leaf spotting diseases, tan spot, caused by an ascomycete fungus Pyrenophora tritici-repentis, and Stagonospora nodorum blotch besides causing average yield losses of 5?10%, cause significant losses in grain quality by red smudge, black point and grain shriveling. Conservation agriculture in combination with wheat monoculture involving cultivation of susceptible cultivars has resulted in frequent onset of leaf spots epidemics worldwide. Development of resistant wheat cultivars, in conjunction with crop rotation, will provide an effective, economical, and environmentally safe means of controlling leaf spot. International Maize and Wheat Improvement Center (CIMMYT), Mexico has initiated major efforts to mitigate the threat of tan spot. Efforts include screening of wheat germplasm, identification of new sources of resistance, characterization of new tan spot resistance genes through classical and molecular genetic analysis, incorporation of resistance into adapted cultivars, and assessing the variability in the tan spot fungus. Screening studies reveal that elite CIMMYT germplasm has high level of resistance to tan spot caused by P. tritici-repentis race 1. These germplasm have diverse genetic make-up and the resistance is likely broad based. Association mapping studies done with CIMMYT germplasm reconfirmed the presence of previously identified genomic regions for tan spot resistance; however, novel genomic regions on long arm of chromosomes 6A and 7B have also been identified. Studies done to date indicate that CIMMYT germplasm possess high level diverse genetic based resistance to tan spot of wheat. Efforts are in place to develop desired wheat cultivars with tan spot resistance. Virulence studies indicate presence of P. tritici-repentis race 1 only with some variability in level of toxin Ptr ToxA produced in each of the 76 isolates studied.
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  • Transferencia del gen Lr14a de trigos harineros a trigos cristalinos y expresion de la resistencia a roya de la hoja
    (Sociedad Mexicana de Fitogenética, 2010) Huerta-Espino, J.; Singh, R.P.; Villaseñor Mir, H.E.; Solís Moya, E.; Espitia-Rangel, E.; Leyva Mir, S.G
    El origen del gen de resistencia Lr14a a roya de la hoja causada por Puccinia triticina E. es el trigo tetraploide 'Yaroslav emmer' (Triticum dicoccum L.). En México, todas las razas de trigo harinero (T. aestivum) importantes son virulentas a este gen. Sin embargo, las razas que atacan trigos cristalinos o duros son avirulentas a Lr14a. Se ha determinado la presencia de Lr14a en trigo harinero y en especies silvestres tetraploides, pero no en trigos cristalinos o trigos duros (T. turgidum spp durum). El gen Lr14a se transfirió a la variedad cristalina 'Altar C84' a partir de la cruza de ésta con la línea monogénica de trigo harinero 'RL6013' (Selkirk/6*Thatcher) y una retrocruza hacia 'Altar C84'. Para determinar la genética de la resistencia de la variedad 'Jupare C2001', resistente a la raza de roya de la hoja que venció la resistencia de 'Altar C84', y determinar si 'Jupare C2001' posee Lr14a, se cruzó con 'Altar C84' y con 'Altar C84' +Lr14a. La respuesta del gen de resistencia a roya de la hoja Lr14a a la infección en plántula a las razas BBG/BN y BCG/BN que son virulentas en 'Altar C84', es de heterogénea con uredinios grandes (X a X+) en la escala de 0–4, tanto en trigos harineros como en 'Altar C84', mientras que confiere casi inmunidad en planta adulta a estas mismas razas. La cruza de 'Jupare C2001' con 'Altar C84' +Lr14a indicó que 'Jupare C2001' no posee Lr14a, y que la resistencia de esta última se basa en dos genes complementarios dominantes. Para el funcionamiento efectivo de la resistencia que el gen Lr14a confiere en trigos cristalinos en respuesta a las razas de roya de la hoja que preferentemente atacan trigos harineros, es necesaria la presencia del gen de 'Altar C84'.
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  • Genetica de la resistencia a roya amarilla en plantas adultas de trigo harinero
    (Sociedad Mexicana de Fitogenética, 2009) Villaseñor-Espin, O.M.; Huerta-Espino, J.; Leyva Mir, S.G; Villaseñor Mir, H.E.; Singh, R.P.; Sandoval Islas, J.S.; Espitia-Rangel, E.
    La roya lineal amarilla del trigo (Triticum aestivum L.) causada por Puccinia striiformis f. sp. tritici es una enfermedad de creciente importancia en los Valles Altos de México, pues llega a causar perdidas en el rendimiento mayores a 60 % y deteriora la calidad del grano. Las variedades de trigo harinero 'Juchi F2000', 'Nahuatl F2000' y 'Tlaxcala F2000' fueron Iiberadas por el Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias en el año 2000 para siembras de temporal 0 secano, que mostraron diferentes grados de infección por esta enfermedad. Para determinar la genética de la resistencia a roya amarilla de las tres variedades, estas se cruzaron con la variedad susceptible 'AvocetYrA'. Los progenitores y 148 familias F3 por cruza se evaluaron durante el Verano 2002 en Toluca, Estado de México, bajo una incidencia natural de roya amarilla. Con los resultados de las familias F3 se determinó que la resistencia de planta adulta a roya amarilla en 'Juchi F2000' esta regalada por tres genes menores de efectos aditivos, y que en 'Nahuatl F2000' y 'Tlaxcala F2000' está condicionada por tres 0 cuatro genes de la misma naturaleza. Un gen en común en las tres variedades fue Yr18, que confiere resistencia parcial de planta adulta a roya amarilla. La progenie de 'Nahuatl F2000' manifestó mayor nivel de resistencia, 10 que indica fue contiene más genes 0 genes diferentes y más efectivos; por ello, a través de una cruza triple entre las tres variedades podría aumentarse el nivel de resistencia a roya amarilla.
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