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2.
Euphytica ; 215(4): 80, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31057179

RESUMO

After drought, a major challenge to smallholder farmers in sub-Saharan Africa is low-fertility soils with poor nitrogen (N)-supplying capacity. Many challenges in this region need to be overcome to create a viable fertilizer market. An intermediate solution is the development of maize varieties with an enhanced ability to take up or utilize N in severely depleted soils, and to more efficiently use the small amounts of N that farmers can supply to their crops. Over 400 elite inbred lines from seven maize breeding programs were screened to identify new sources of tolerance to low-N stress and maize lethal necrosis (MLN) for introgression into Africa-adapted elite germplasm. Lines with high levels of tolerance to both stresses were identified. Lines previously considered to be tolerant to low-N stress ranked in the bottom 10% under low-N confirming the need to replace these lines with new donors identified in this study. The lines that performed best under low-N yielded about 0. 5 Mg ha-1 (20%) more in testcross combinations than some widely used commercial parent lines such as CML442 and CML395. This is the first large scale study to identify maize inbred lines with tolerance to low-N stress and MLN in eastern and southern Africa.

3.
Plant Methods ; 14: 49, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29946344

RESUMO

Background: Grain yield, ear and kernel attributes can assist to understand the performance of maize plant under different environmental conditions and can be used in the variety development process to address farmer's preferences. These parameters are however still laborious and expensive to measure. Results: A low-cost ear digital imaging method was developed that provides estimates of ear and kernel attributes i.e., ear number and size, kernel number and size as well as kernel weight from photos of ears harvested from field trial plots. The image processing method uses a script that runs in a batch mode on ImageJ; an open source software. Kernel weight was estimated using the total kernel number derived from the number of kernels visible on the image and the average kernel size. Data showed a good agreement in terms of accuracy and precision between ground truth measurements and data generated through image processing. Broad-sense heritability of the estimated parameters was in the range or higher than that for measured grain weight. Limitation of the method for kernel weight estimation is discussed. Conclusion: The method developed in this work provides an opportunity to significantly reduce the cost of selection in the breeding process, especially for resource constrained crop improvement programs and can be used to learn more about the genetic bases of grain yield determinants.

4.
Curr Opin Plant Biol ; 45(Pt B): 226-230, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-29779966

RESUMO

In sub-Saharan Africa (SSA) and Asia maize yields remain variable due to climate shocks. Over the past decade extensive progress has been made on the development and delivery of climate-resilient maize. In 2016 over 70000 metric tonnes of drought-tolerant maize seed was commercialized in 13 countries in SSA, benefiting an estimated 53 million people. Significant progress is also being made with regard to the development and deployment of elite heat-tolerant maize varieties in South Asia. Increased genetic gain in grain yield under stress-prone environments, coupled with faster replacement of old/obsolete varieties, through intensive engagement with seed companies is essential to protect maize crops grown by smallholders from the changing climates in SSA and Asia.


Assuntos
Zea mays/fisiologia , Ásia , Clima , Produtos Agrícolas/fisiologia
5.
Crop Prot ; 89: 202-208, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27812235

RESUMO

A study was conducted to assess the performance of maize hybrids with Bt event MON810 (Bt-hybrids) against the maize stem borer Busseola fusca (Fuller) in a biosafety greenhouse (BGH) and against the spotted stem borer Chilo partellus (Swinhoe) under confined field trials (CFT) in Kenya for three seasons during 2013-2014. The study comprised 14 non-commercialized hybrids (seven pairs of near-isogenic Bt and non-Bt hybrids) and four non-Bt commercial hybrids. Each plant was artificially infested twice with 10 first instar larvae. In CFT, plants were infested with C. partellus 14 and 24 days after planting; in BGH, plants were infested with B. fusca 21 and 31 days after planting. In CFT, the seven Bt hybrids significantly differed from their non-Bt counterparts for leaf damage, number of exit holes, percent tunnel length, and grain yield. When averaged over three seasons, Bt-hybrids gave the highest grain yield (9.7 t ha-1), followed by non-Bt hybrids (6.9 t ha-1) and commercial checks (6 t ha-1). Bt-hybrids had the least number of exit holes and percent tunnel length in all the seasons as compared to the non-Bt hybrids and commercial checks. In BGH trials, Bt-hybrids consistently suffered less leaf damage than their non-Bt near isolines. The study demonstrated that MON810 was effective in controlling B. fusca and C. partellus. Bt-maize, therefore, has great potential to reduce the risk of maize grain losses in Africa due to stem borers, and will enable the smallholder farmers to produce high-quality grain with increased yield, reduced insecticide inputs, and improved food security.

6.
Plant Methods ; 11: 35, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26106438

RESUMO

BACKGROUND: Recent developments in unmanned aerial platforms (UAP) have provided research opportunities in assessing land allocation and crop physiological traits, including response to abiotic and biotic stresses. UAP-based remote sensing can be used to rapidly and cost-effectively phenotype large numbers of plots and field trials in a dynamic way using time series. This is anticipated to have tremendous implications for progress in crop genetic improvement. RESULTS: We present the use of a UAP equipped with sensors for multispectral imaging in spatial field variability assessment and phenotyping for low-nitrogen (low-N) stress tolerance in maize. Multispectral aerial images were used to (1) characterize experimental fields for spatial soil-nitrogen variability and (2) derive indices for crop performance under low-N stress. Overall, results showed that the aerial platform enables to effectively characterize spatial field variation and assess crop performance under low-N stress. The Normalized Difference Vegetation Index (NDVI) data derived from spectral imaging presented a strong correlation with ground-measured NDVI, crop senescence index and grain yield. CONCLUSION: This work suggests that the aerial sensing platform designed for phenotyping studies has the potential to effectively assist in crop genetic improvement against abiotic stresses like low-N provided that sensors have enough resolution for plot level data collection. Limitations and future potential uses are also discussed.

7.
Heredity (Edinb) ; 114(3): 291-9, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25407079

RESUMO

One of the most important applications of genomic selection in maize breeding is to predict and identify the best untested lines from biparental populations, when the training and validation sets are derived from the same cross. Nineteen tropical maize biparental populations evaluated in multienvironment trials were used in this study to assess prediction accuracy of different quantitative traits using low-density (~200 markers) and genotyping-by-sequencing (GBS) single-nucleotide polymorphisms (SNPs), respectively. An extension of the Genomic Best Linear Unbiased Predictor that incorporates genotype × environment (GE) interaction was used to predict genotypic values; cross-validation methods were applied to quantify prediction accuracy. Our results showed that: (1) low-density SNPs (~200 markers) were largely sufficient to get good prediction in biparental maize populations for simple traits with moderate-to-high heritability, but GBS outperformed low-density SNPs for complex traits and simple traits evaluated under stress conditions with low-to-moderate heritability; (2) heritability and genetic architecture of target traits affected prediction performance, prediction accuracy of complex traits (grain yield) were consistently lower than those of simple traits (anthesis date and plant height) and prediction accuracy under stress conditions was consistently lower and more variable than under well-watered conditions for all the target traits because of their poor heritability under stress conditions; and (3) the prediction accuracy of GE models was found to be superior to that of non-GE models for complex traits and marginal for simple traits.


Assuntos
Genômica/métodos , Polimorfismo de Nucleotídeo Único , Característica Quantitativa Herdável , Zea mays/genética , Cruzamento , Interação Gene-Ambiente , Genótipo , Modelos Genéticos , Modelos Estatísticos , Fenótipo , Estresse Fisiológico , Água/fisiologia
8.
Theor Appl Genet ; 126(11): 2671-82, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23921956

RESUMO

Maize was first domesticated in a restricted valley in south-central Mexico. It was diffused throughout the Americas over thousands of years, and following the discovery of the New World by Columbus, was introduced into Europe. Trade and colonization introduced it further into all parts of the world to which it could adapt. Repeated introductions, local selection and adaptation, a highly diverse gene pool and outcrossing nature, and global trade in maize led to difficulty understanding exactly where the diversity of many of the local maize landraces originated. This is particularly true in Africa and Asia, where historical accounts are scarce or contradictory. Knowledge of post-domestication movements of maize around the world would assist in germplasm conservation and plant breeding efforts. To this end, we used SSR markers to genotype multiple individuals from hundreds of representative landraces from around the world. Applying a multidisciplinary approach combining genetic, linguistic, and historical data, we reconstructed possible patterns of maize diffusion throughout the world from American "contribution" centers, which we propose reflect the origins of maize worldwide. These results shed new light on introductions of maize into Africa and Asia. By providing a first globally comprehensive genetic characterization of landraces using markers appropriate to this evolutionary time frame, we explore the post-domestication evolutionary history of maize and highlight original diversity sources that may be tapped for plant improvement in different regions of the world.


Assuntos
Internacionalidade , Zea mays/genética , América , Análise por Conglomerados , Loci Gênicos , Variação Genética , Geografia , Repetições de Microssatélites/genética , Filogenia , Análise de Componente Principal
9.
J Biosci ; 37(5): 843-55, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23107920

RESUMO

Maize (Zea mays L.) is not only of worldwide importance as a food, feed and as a source of diverse industrially important products, but is also a model genetic organism with immense genetic diversity. Although it was first domesticated in Mexico, maize landraces are widely found across the continents. Several studies in Mexico and other countries highlighted the genetic variability in the maize germplasm. Applications of molecular markers, particularly in the last two decades, have led to new insights into the patterns of genetic diversity in maize globally, including landraces as well as wild relatives (especially teosintes) in Latin America, helping in tracking the migration routes of maize from the centers of origin, and understanding the fate of genetic diversity during maize domestication. The genome sequencing of B73 (a highly popular US Corn Belt inbred) and Palomero (a popcorn landrace in Mexico) in the recent years are important landmarks in maize research, with significant implications to our understanding of the maize genome organization and evolution. Next-generation sequencing and high-throughput genotyping platforms promise to further revolutionize our understanding of genetic diversity and for designing strategies to utilize the genomic information for maize improvement. However, the major limiting factor to exploit the genetic diversity in crops like maize is no longer genotyping, but high-throughput and precision phenotyping. There is an urgent need to establish a global phenotyping network for comprehensive and efficient characterization of maize germplasm for an array of target traits, particularly for biotic and abiotic stress tolerance and nutritional quality. 'Seeds of Discovery' (SeeD), a novel initiative by CIMMYT with financial support from the Mexican Government for generating international public goods, has initiated intensive exploration of phenotypic and molecular diversity of maize germplasm conserved in the CIMMYT Gene Bank; this is expected to aid in effective identification and use of novel alleles and haplotypes for maize improvement. Multi-institutional efforts are required at the global level to systematically explore the maize germplasm to diversify the genetic base of elite breeding materials, create novel varieties and counter the effects of global climate changes.


Assuntos
Variação Genética , Genoma de Planta , Haplótipos , Fenótipo , Sementes/genética , Zea mays/genética , Alelos , Evolução Biológica , Bancos de Espécimes Biológicos , Mapeamento Cromossômico , Sequenciamento de Nucleotídeos em Larga Escala , Cooperação Internacional , México , Filogenia , Polimorfismo de Nucleotídeo Único , Sementes/classificação , Zea mays/classificação
10.
Theor Appl Genet ; 125(7): 1487-501, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22801872

RESUMO

Quality control (QC) genotyping is an important component in breeding, but to our knowledge there are not well established protocols for its implementation in practical breeding programs. The objectives of our study were to (a) ascertain genetic identity among 2-4 seed sources of the same inbred line, (b) evaluate the extent of genetic homogeneity within inbred lines, and (c) identify a subset of highly informative single-nucleotide polymorphism (SNP) markers for routine and low-cost QC genotyping and suggest guidelines for data interpretation. We used a total of 28 maize inbred lines to study genetic identity among different seed sources by genotyping them with 532 and 1,065 SNPs using the KASPar and GoldenGate platforms, respectively. An additional set of 544 inbred lines was used for studying genetic homogeneity. The proportion of alleles that differed between seed sources of the same inbred line varied from 0.1 to 42.3 %. Seed sources exhibiting high levels of genetic distance are mis-labeled, while those with lower levels of difference are contaminated or still segregating. Genetic homogeneity varied from 68.7 to 100 % with 71.3 % of the inbred lines considered to be homogenous. Based on the data sets obtained for a wide range of sample sizes and diverse genetic backgrounds, we recommended a subset of 50-100 SNPs for routine and low-cost QC genotyping, verified them in a different set of double haploid and inbred lines, and outlined a protocol that could be used to minimize errors in genetic analyses and breeding.


Assuntos
Técnicas de Genotipagem/métodos , Técnicas de Genotipagem/normas , Endogamia , Clima Tropical , Zea mays/genética , Alelos , Heterogeneidade Genética , Loci Gênicos/genética , Genótipo , Haploidia , Filogenia , Polimorfismo de Nucleotídeo Único/genética , Controle de Qualidade , Seleção Genética
11.
BMC Genomics ; 13: 113, 2012 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-22443094

RESUMO

BACKGROUND: Knowledge of germplasm diversity and relationships among elite breeding materials is fundamentally important in crop improvement. We genotyped 450 maize inbred lines developed and/or widely used by CIMMYT breeding programs in both Kenya and Zimbabwe using 1065 SNP markers to (i) investigate population structure and patterns of relationship of the germplasm for better exploitation in breeding programs; (ii) assess the usefulness of SNPs for identifying heterotic groups commonly used by CIMMYT breeding programs; and (iii) identify a subset of highly informative SNP markers for routine and low cost genotyping of CIMMYT germplasm in the region using uniplex assays. RESULTS: Genetic distance for about 94% of the pairs of lines fell between 0.300 and 0.400. Eighty four percent of the pairs of lines also showed relative kinship values ≤ 0.500. Model-based population structure analysis, principal component analysis, neighbor-joining cluster analysis and discriminant analysis revealed the presence of 3 major groups and generally agree with pedigree information. The SNP markers did not show clear separation of heterotic groups A and B that were established based on combining ability tests through diallel and line x tester analyses. Our results demonstrated large differences among the SNP markers in terms of reproducibility, ease of scoring, polymorphism, minor allele frequency and polymorphic information content. About 40% of the SNPs in the multiplexed chip-based GoldenGate assays were found to be uninformative in this study and we recommend 644 of the 1065 for low to medium density genotyping in tropical maize germplasm using uniplex assays. CONCLUSIONS: There were high genetic distance and low kinship coefficients among most pairs of lines, clearly indicating the uniqueness of the majority of the inbred lines in these maize breeding programs. The results from this study will be useful to breeders in selecting best parental combinations for new breeding crosses, mapping population development and marker assisted breeding.


Assuntos
Cruzamento , Técnicas de Genotipagem/métodos , Polimorfismo de Nucleotídeo Único/genética , Zea mays/genética , África , Marcadores Genéticos/genética , Técnicas de Genotipagem/economia , Células Germinativas/metabolismo , Zea mays/citologia
12.
Genetica ; 138(6): 619-31, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20107870

RESUMO

The maize landraces in the North East Himalayan (NEH) region in India, especially in the Sikkim state, are morphologically highly diverse. The present study provides details of phenotypic and molecular characterization of a set of 48 selected maize landrace accessions, including the 'Sikkim Primitives' which have a unique habit of prolificacy (5-9 ears on a single stalk). Multi-location phenotypic evaluation of these 48 accessions revealed significant genetic variability for grain yield and its components, leading to identification of several promising accessions. Cluster analysis and PCA using nine morpho-agronomic characters clearly separated 'Sikkim Primitives' from the rest of the accessions. PCA revealed two principal components describing 90% of the total variation, with hundred kernel weight, ear length, ear diameter, number of kernels per ear and flowering behaviour forming the most discriminatory traits. The accessions were genotyped using 42 microsatellite or simple sequence repeat (SSR) markers using a 'population bulk DNA fingerprinting strategy', with allele resolution using an automated DNA Sequencer. The study revealed a high mean number of alleles per SSR locus (13.0) and high Polymorphism Information Content (PIC) value of 0.60. The analysis also led to identification of 163 private/unique alleles, differentiating 44 out of 48 accessions. Six highly frequent SSR alleles were detected at different loci (phi014, phi062, phi090, umc1266, umc1367 and umc2250) with individual frequencies >/=0.75. Some of these SSR loci were reported to tag specific genes/QTL for some important traits, indicating that chromosomal regions harboring these SSR alleles were not selectively neutral. Cluster analysis using Rogers' genetic distance also revealed distinct genetic identity of the 'Sikkim Primitives' from the rest of the accessions in India, including Sikkim. Mantel's test revealed significant and positive correlation between the phenotypic and molecular genetic dissimilarity matrices. The study was the first to portray the patterns of phenotypic and molecular diversity in the maize landraces from the NEH region in India.


Assuntos
Repetições de Microssatélites/genética , Zea mays/genética , Alelos , Índia , Fenótipo , Polimorfismo Genético , Locos de Características Quantitativas , Zea mays/classificação
13.
Folia Microbiol (Praha) ; 53(1): 35-43, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18481216

RESUMO

The cyanobionts isolated from 10 Azolla accessions belonging to 6 species (Azolla mexicana, A. microphylla, A. rubra, A. caroliniana, A. filiculoides, A. pinnata) were cultured under laboratory conditions and analyzed on the basis of whole cell protein profiles and molecular marker dataset generated using repeat sequence primers (STRR(mod) and HipTG). The biochemical and molecular marker profiles of the cyanobionts were compared with those of the free-living cyanobacteria and symbiotic Nostoc strains from Anthoceros sp., Cycas sp. and Gunnera monoika. Cluster analysis revealed the genetic diversity among the selected strains, and identified 3 distinct clusters. Group 1 included cyanobionts from all the 10 accessions of Azolla, group 2 comprised all the symbiotic Nostoc strains, while group 3 included the free-living cyanobacteria belonging to the genera Nostoc and Anabaena. The interrelationships among the Azolla cyanobionts were further revealed by principal component analysis. Cyanobionts from A. caroliniana-A. microphylla grouped together while cyanobionts associated with A. mexicana-A. filiculoides along with A. pinnata formed another group. A. rubra cyanobionts had intermediate relationship with both the subgroups. This is the first study analyzing the diversity existing among the cultured cyanobionts of diverse Azolla species through the use of biochemical and molecular profiles and also the genetic distinctness of these free-living cyanobionts as compared to cyanobacterial strains of the genera Anabaena and Nostoc.


Assuntos
Cianobactérias/classificação , Cianobactérias/genética , Gleiquênias/microbiologia , Variação Genética , Simbiose , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Técnicas de Cultura , Cianobactérias/isolamento & purificação , Cianobactérias/metabolismo , Dados de Sequência Molecular , Filogenia
14.
Microbiol Res ; 161(3): 187-202, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-16765835

RESUMO

A set of 30 Anabaena strains, isolated from diverse geographical regions of India, were characterized using morphological and physiochemical attributes as well as molecular marker profiles. Significant differences were observed among the Anabaena strains with regard to the shape and size of trichomes and individual cells within a filament, besides qualitative and quantitative aspects of phycobiliprotein accumulation and activities of enzymes involved in nitrogen metabolism. Analyses of molecular polymorphisms in a selected set of 13 Anabaena strains, using primers based on repetitive sequences in the genome, led to unambiguous differentiation of the strains as well as understanding of their genetic relationships. Informative morphological, physio-chemical and molecular characters have been identified that could aid in differentiation and utilization of Anabaena strains as bioinoculants or as sources of pigments.


Assuntos
Anabaena/classificação , Anabaena/citologia , Anabaena/fisiologia , Primers do DNA , Genoma Bacteriano , Índia , Complexos de Proteínas Captadores de Luz/análise , Complexos de Proteínas Captadores de Luz/metabolismo , Nitrogênio/metabolismo , Polimorfismo Genético , Especificidade da Espécie
15.
Theor Appl Genet ; 110(8): 1384-92, 2005 May.
Artigo em Inglês | MEDLINE | ID: mdl-15841363

RESUMO

We have mapped the quantitative trait loci (QTLs) conferring resistance to sorghum downy mildew (Peronosclerospora sorghi; SDM) and Rajasthan downy mildew (P. heteropogoni; RDM), two species of DM prevalent throughout India. QTL mapping was carried out on a backcross population of 151 individuals derived from a cross between CM139 (susceptible parent) and NAI116 (highly resistant to both SDM and RDM). Heritability estimates were 0.74 for SDM and 0.67 for RDM. Composite interval mapping combined with a linkage map constructed with 80 simple sequence repeat (SSR) markers resulted in the identification of three QTLs (one each on chromosomes 2, 3 and 6) for SDM resistance and two QTLs (one each on chromosomes 3 and 6) for RDM resistance, all of which were contributed by NAI116. The significance of the major QTL on chromosome 6 (bin 6.05) that confers resistance to diverse DMs in tropical Asia, including SDM and RDM in India, was also verified. The results confirmed that some common QTLs contribute to both SDM and RDM resistance, while additional loci might specifically govern resistance to SDM. The QTL information generated in this study provide information that will aid in undertaking an integrated breeding strategy for the transfer of resistance to SDM and RDM in maize lines using marker-assisted selection.


Assuntos
Mapeamento Cromossômico , Imunidade Inata/genética , Oomicetos , Doenças das Plantas/microbiologia , Locos de Características Quantitativas , Zea mays/genética , Cruzamento/métodos , Cruzamentos Genéticos , Índia , Repetições Minissatélites/genética , Zea mays/microbiologia
16.
Folia Microbiol (Praha) ; 48(1): 59-64, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-12744078

RESUMO

Twenty Tolypothrix strains, including 15 strains of T. tenuis, three strains of T. ceylonica and one strain each of T. nodosa and T. bouteillei, were evaluated for their phycobiliprotein content and composition. Significant differences among the Tolypothrix strains were found at both inter- and intra-specific levels in the production of phycobiliprotein constituents--phycocyanin (PC), allophycocyanin (APC) and phycoerythrin (PE). Four specific parameters, viz. PC or PE content, total phycobiliprotein and total protein content, and percentage of phycobiliproteins, in a mixture of total proteins were used to select four T. tenuis and one T. ceylonica strain as useful for phycobiliproteins production.


Assuntos
Proteínas de Bactérias/biossíntese , Cianobactérias/classificação , Cianobactérias/metabolismo , Biossíntese de Proteínas , Proteínas de Bactérias/química , Biotecnologia/métodos , Meios de Cultura , Cianobactérias/crescimento & desenvolvimento , Complexos de Proteínas Captadores de Luz , Pigmentos Biológicos/biossíntese , Proteínas/análise , Especificidade da Espécie
17.
Theor Appl Genet ; 107(3): 544-51, 2003 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-12759731

RESUMO

Downy mildew is one of the most destructive diseases of maize in subtropical and tropical regions in Asia. As a prerequisite for improving downy mildew resistance in maize, we analyzed quantitative trait loci (QTLs) involved in resistance to the important downy mildew pathogens--Peronosclerospora sorghi (sorghum downy mildew) and P. heteropogoni (Rajasthan downy mildew) in India, P. maydis (Java downy mildew) in Indonesia, P. zeae in Thailand and P. philippinensis in the Philippines--using a recombinant inbred line population derived from a cross between Ki3 (downy mildew resistant) and CML139 (susceptible). Resistance was evaluated as percentage disease incidence in replicated field trials at five downy mildew 'hotspots' in the four countries. Heritability estimates of individual environments ranged from 0.58 to 0.75 with an across environment heritability of 0.50. Composite interval mapping was applied for QTL detection using a previously constructed restriction fragment length polymorphism linkage map. The investigation resulted in the identification of six genomic regions on chromosomes 1, 2, 6, 7 and 10 involved in the resistance to the downy mildews under study, explaining, in total, 26-57% of the phenotypic variance for disease response. Most QTL alleles conferring resistance to the downy mildews were from Ki3. All QTLs showed significant QTL x environment interactions, suggesting that the expression of the QTL may be environment-dependent. A strong QTL on chromosome 6 was stable across environments, significantly affecting disease resistance at the five locations in four Asian countries. Simple-sequence repeat markers tightly linked to this QTL were identified for potential use in marker-assisted selection.


Assuntos
Imunidade Inata/genética , Oomicetos , Doenças das Plantas/genética , Locos de Características Quantitativas/genética , Zea mays/genética , Ásia , Mapeamento Cromossômico , Cruzamentos Genéticos , Repetições Minissatélites/genética , Fenótipo
18.
Diabetes Res Clin Pract ; 27(2): 127-32, 1995 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-7607050

RESUMO

The exocrine and endocrine pathophysiology of chronic calcific pancreatitis of the tropics (CCPT) remains elusive. The objective of this study was to evaluate the spectrum and correlates of the exocrine and endocrine pancreatic dysfunction in CCPT. Thirty-seven consecutive patients with a clinico-radiological diagnosis of CCPT were stratified into three subgroups: CCPT-normal glucose tolerance (NGT), CCPT-abnormal glucose tolerance (IGT) and CCPT-diabetes mellitus (DM). Ten ketosis resistant young diabetic (KRDY) patients, 10 classical insulin dependent diabetes mellitus (IDDM) patients and 18 healthy matched controls were included for comparison. Fecal chymotrypsin (FCT) levels and blood C-peptide levels (basal and post i.v. glucagon stimulation) were estimated for assessing the exocrine and endocrine pancreatic functions, respectively. Sonography was performed to evaluate the pancreatic size and ductal diameter. Pancreatic exocrine-endocrine correlation was examined by studying the C-peptide/fecal chymotrypsin ratio (CP/FCT) (CP/FCT of normal controls = 1). Mean FCT levels in all 3 subgroups of CCPT (NGT: 3.4 micrograms/g; IGT: 0.82 microgram/g; DM: 2.4 micrograms/g) were very low (87-96% reduction in exocrine pancreatic dysfunction; mean FCT in healthy controls was 22.8 micrograms/g) (P < 0.0001). In contrast, KRDY and IDDM patients displayed 50-54% reduction in pancreatic acinar function (P < 0.001). Basal and stimulated C-peptide levels progressively fell in the 3 CCPT subsets (NGT: 0.23 and 0.46 > IGT: 0.14 and 0.29 > DM 0.10 and 0.14) (P < 0.01). CCPT patients exhibited pancreatic atrophy and ductal dilation (> 3 mm).(ABSTRACT TRUNCATED AT 250 WORDS)


Assuntos
Peptídeo C/sangue , Calcinose/fisiopatologia , Quimotripsina/análise , Diabetes Mellitus Tipo 1/fisiopatologia , Diabetes Mellitus Tipo 2/fisiopatologia , Ilhotas Pancreáticas/fisiopatologia , Pâncreas/fisiopatologia , Pancreatite/fisiopatologia , Adolescente , Adulto , Idade de Início , Análise de Variância , Glicemia/metabolismo , Doença Crônica , Feminino , Glucagon , Intolerância à Glucose/fisiopatologia , Teste de Tolerância a Glucose , Humanos , Masculino , Pâncreas/diagnóstico por imagem , Pancreatite/diagnóstico por imagem , Valores de Referência , Clima Tropical , Ultrassonografia
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