CIMMYT Library Blog

Published in:  BMC Plant Biology 2010, 10:143 / 10.1186/1471-2229-10-143 

Relationship, evolutionary fate and function of two maize co-orthologs of rice GW2 associated with kernel size and weight 

Qing Li, Lin Li, Xiaohong Yang, Marilyn L Warburton, Guanghong Bai, Jingrui Dai, Jiansheng Li, Jianbing Yan 

Background: In rice, the GW2 gene, found on chromosome 2, controls grain width and weight. Two homologs of this gene, ZmGW2-CHR4 and ZmGW2-CHR5, have been found in maize. In this study, we investigated the relationship, evolutionary fate and putative function of these two maize genes. Results: The two genes are located on duplicated maize chromosomal regions that show co-orthologous relationships with the rice region containing GW2. ZmGW2-CHR5 is more closely related to the sorghum counterpart than to ZmGW2-CHR4. Sequence comparisons between the two genes in eight diverse maize inbred lines revealed that the functional protein domain of both genes is completely conserved, with no nonsynonymous polymorphisms identified. This suggests that both genes may have conserved functions, a hypothesis that was further confirmed through linkage, association, and expression analyses. Linkage analysis showed that ZmGW2-CHR4 is located within a consistent quantitative trait locus (QTL) for one-hundred kernel weight (HKW). Association analysis with a diverse panel of 121 maize inbred lines identified one single nucleotide polymorphism (SNP) in the promoter region of ZmGW2-CHR4 that was significantly associated with kernel width (KW) and HKW across all three field experiments examined in this study. SNPs or insertion/deletion polymorphisms (InDels) in other regions of ZmGW2-CHR4 and ZmGW2-CHR5 were also found to be significantly associated with at least one of the four yield-related traits (kernel length (KL), kernel thickness (KT), KW and HKW). None of the polymorphisms in either maize gene are similar to each other or to the 1 bp InDel causing phenotypic variation in rice. Expression levels of both maize genes vary over ear and kernel developmental stages, and the expression level of ZmGW2- CHR4 is significantly negatively correlated with KW. Conclusions: The sequence, linkage, association and expression analyses collectively showed that the two maize genes represent chromosomal duplicates, both of which function to control some of the phenotypic variation for kernel size and weight in maize, as does their counterpart in rice. However, the different polymorphisms identified in the two maize genes and in the rice gene indicate that they may cause phenotypic variation through different mechanisms.

Published in:  S. Afr. J. Plant & Soil 2010, 27(3) 

Targeting of early to intermediate maize hybrids for yield performance and yield stability using SREG model 

P.S. Setimela, J. Crossa and M. Bänziger 

The effectiveness of targeting and predicting maize (Zea mays.L) hybrid performance is difficult when the magnitude of genotype x environment (GE) interaction and yield prediction cannot be interpreted and is only based on genotypes (G) and GE means. The traditional analysis of variance (ANOVA) is not sufficient in predicting and giving information into the patterns of genotypes and environments that give rise to GE interaction. The objectives of this study were to show the usefulness of G plus GE interaction (GGE) using the properties of GGE biplot based on the site regression (SREG) model analysis of a biplot in predicting yield performance and stability of early to intermediate maturing hybrids (EIHYB) grown in southern Africa. The SREG analysis model was based on regional trial data of EIHYB from three seasons (2005 – 2007) across 30 environments under four different management practices: well fertilized/rain fed conditions, managed nitrogen stress, managed drought stress, and managed low pH stress. GGE biplots were constructed using the first two principal components (PC1 and PC2) derived from singular value decomposition of environment-centered multi-environmental trials. The PC1 scores of the hybrids and the environments were plotted against their respective PC2 scores to effectively show mean performance and stability for grain yield across years and environments; discriminativeness vs. representativeness of test locations across the years and which-won-where. The SREG model showed that maize hybrids were under major environmental and GE interactions. In spite of large variation from year to year maize hybrids responded positively to better environmental conditions relative to grain yield performance and key environmental patterns could be established.

Published in:  ACTA AGRONÓMICA. 59 (2) 2010, p 162-169 

Evaluación de poblaciones F2 de maíz de alta calidad de proteína en los Llanos Orientales de Colombia/ Evaluation of maize genotypes with high quality protein for the Eastern Plains of Colombia 

Claudia Milena Pérez P.,Luis Alberto Narro L. y Óscar Eduardo Checa C. 

RESUMEN: Doscientas cincuenta y tres familias F2 de alta calidad de proteína (ACP) provenientes del CIMMYT (Centro Internacional de Mejoramiento de Maíz y Trigo) fueron evaluadas en dos ensayos diferentes en Menegua, una localidad ubicada en el departamento del Meta de los Llanos Orientales de Colombia. El diseño experimental utilizado fue de alpha lattice con 2 repeticiones y en cada ensayo se incluyó testigos ACP y normales. Los datos fueron analizados siguiendo el método REML (Restricted maximum Likelihood Method) del procedimiento GLM de SAS 9.1.3. Los criterios principales de selección fueron rendimiento de grano y textura de grano. Se seleccionaron 44 F2s con rendimiento superior al del testigo ACP y comparable al rendimiento de los testigos normales. La textura de grano de las familias seleccionadas fue semi-cristalino con buena dosis de genes modificadores lo que indica que el gen o2 está presente. El paso siguiente será seguir el proceso de autofecundación de las familias F2 hasta llegar a F5 en que se hará los cruzamientos con probadores a fin de identificar líneas deseables para la formación de híbridos y sintéticos.  

ABSTRACT: The objective of the work was to select genotypes with high quality protein maize (QPM) and adapted to acid soils. Corn populations F2 of QPM were evaluated in the eastern plains of Colombia, by the International Maize and Wheat Improvement Center (CIMMYT) México. Populations were divided in two groups of 70 and 90 genotypes. The experimental designs consisted on a Alpha Lattice of 10×7 and 10×9, with two repetitions, were. The main criteria of selection were grain yield (t/ha) and texture of endosperm, as indicator of modifier genes. The experiments were analyzed using the procedures MIXED and GLM with the Maxima method Restricted Probability (REML) of SAS 9.1.3. With the Alpha Lattice of 10×7, the results indicated that under conditions of acidity, the best genotype, accession 54 with 4,86t/ha, was similar to the commercial hybrid H-108 check. This material showed good texture also. In the Alpha Lattice of 10×9, the commercial material with greater yield was HEZC- 318 (7.57 t/ha) and the best accession, 33 and 77 did not out yield it, but the texture was good. The evaluation for modification of endosperm with the light table, 44 families F2 showed the presence of the gene opaque 2 that transfers the ACP characteristics and high yield.

Published in:  Field Crops Research 117 (2010) 101–112 / 10.1016/j.fcr.2010.02.001 

Genetic gains for grain yield in high latitude spring wheat grown in Western Siberia in 1900–2008 

A. Morgounov, V. Zykin, I. Belan, L. Roseeva, Yu. Zelenskiy, Hugo Ferney Gomez-Becerra, H. Budak, F. Bekes  

Short season high latitude (50◦N–56◦N) spring wheat (Triticum aestivum L.) is grown on approximately 7 million ha in Western Siberia with average yield of 1.5–2.0 t/ha. A historical set of 47 varieties developed and grown in the region between 1900 and 2000 was evaluated at a trial in Siberian Research Institute of Agriculture (Omsk) in 2002–2008. The genetic gains for grain yield and associated changes in agronomic traits were analyzed for three maturity groups (early, medium and late) and four breeding periods (before 1930, 1950–1975, 1976–1985 and after 1985). The overall yield was 3.71 t/ha for modern varieties versus 2.18 t/ha for old varieties representing 0.7% increase per year in the course of 100 years. The genetic gains between the breeding periods indicated that the rate of progress for the early and medium maturity groups was more or less comparable from one breeding period to the other. For the late maturity group there was an obvious and sharp decline in genetic gain with time. Modern varieties were also characterized by average response to environmental mean and good grain yield stability evaluated according to Eberhart and Russell (1966). Thousand kernel weight and number of grains per unit area were linearly correlated with grain yield and genetic gain over time suggested their importance for breeding progress. Resistance to leaf rust insomemodern varieties sustained and contributed to stability of genetic gains. The yield increase over time was not associated with plant height reduction and incorporation of Rht genes. The maturity range of the newer varieties is narrower compared to old germplasm as they tend to belong to medium maturity group. Translocation 1B.1R had limited contribution to Western Siberian germplasm being observed in only three varieties. The increase in adaptation, yield potential and its stability has been reached due to gradual accumulation of favorable genes through diverse crosses, robust selection and testing system. Resistance to leaf rust and other prevalent pathogens is of paramount importance for future progress.

Published in:  Outlook on AGRICULTURE 2010  39( 2) 121–126 

Assessing the impact of adaptive agricultural research on accelerating technology deployment: The case of zero tillage wheat in India 

Olaf Erenstein and Vijay Laxmi 

A critical assumption in the impact assessment of an agricultural R&D effort is whether the effort in question has a substitute – that is, whether the innovation would also happen under other settings. This paper takes the case of zero tillage wheat in India to explore diverging counterfactual scenarios whereby, in the ‘without’ case, the innovation would not have been introduced or would have been introduced only with a ten-year or five-year lag. The authors quantify how the assumed counterfactual scenario affects various impact assessment indicators. They show that, even when assuming a conservative five-year lag and based on induced supply-shift gains alone, the investment in zero tillage R&D by the international agricultural research system was highly beneficial. The ability of zero tillage to combine cost savings and yield gains, its wide applicability and significant R&D spill-ins contributed to the high returns. The case thus highlights the high potential gains from successful adaptive research, even if the main effect is only to accelerate technology deployment.

Published in:  Plant Breeding 2010 / 10.1111/j.1439-0523.2010.01802.x 

Frequency of photoperiod-insensitive Ppd-A1a alleles in tetraploid, hexaploid and synthetic hexaploid wheat germplasm 

A. R. Bentley, A. S. Turner, N. Gosman, F. J. Leigh, M. Maccaferri, S. Dreisigacker, A.Greenland And D. A. Laurie 

Differences in photoperiod sensitivity are widely used in wheat breeding to provide adaptation to diverse agronomic environments. Two photoperiod insensitive (PI) mutations in the A genome (Ppd-A1a alleles) were previously identified using near-isogenic lines of tetraploid durum wheat. We show that these Ppd-A1a alleles predominate in modern durum wheat but are absent from wild tetraploid wheat and from onventional hexaploid wheat, suggesting they were selected for improved adaptation during durum cultivation. To increase genetic diversity in hexaploid wheat, synthetic hexaploid wheat lines were developed at CIMMYT by hybridizing elite durum lines with Aegilops tauschii accessions. Ppd-A1a alleles from durum wheat were found in 71.4% of 447 synthetic hexaploids and 9.6% of 115 advanced selections. Backcrosses to hexaploid wheat showed that the durum Ppd-A1a alleles conferred a PI phenotype and that one allele was intermediate between known B and D genome mutations, providing a new source of flowering time variation in hexaploid wheat and the potential for novel combinations of PI alleles.

Published in:  Rev. Fitotec. Mex. 2010 Vol. 33 (1): 29 – 36 

Transferencia del gen lr14a de trigos harineros a trigos cristalinos y expresión de la resistencia a roya de la hoja / Transfering the lr14a gene from bread wheat to durum and its expression against leaf rust 

Julio Huerta Espino*, Ravi P. Singh, H. Eduardo Villaseñor Mir, Ernesto Solís Moya, Eduardo Espitia Rangel  y S. Gerardo Leyva Mir 

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’. have been determined, but not in durum wheat. The Lr14a gene was transferred to the cultivar ‘Altar C84’ using the monogenic bread wheat line ‘RL6013’ (Selkirk/6*Thatcher) with the durum wheat ‘Altar C84’ and a backcross to ‘Altar C84’. 

The origin of the resistance gene Lr14a against leaf rust (Puccinia triticina E.) is the tetraploid wheat ‘Yaroslav emmer’ (Triticum dicoccum L.). In Mexico, all the important rust races attacking bread wheat (T. aestivum L.) are virulent to this gene. However, races attacking durum wheat are avirulent to Lr14a. The presence of Lr14a in several bread wheat cultivars and wild tetraploid species have been determined, but not in durum wheat. The Lr14a gene was transferred to the cultivar ‘Altar C84’ using the monogenic bread wheat line ‘RL6013’ (Selkirk/6*Thatcher) with the durum wheat ‘Altar C84’ and a backcross to ‘Altar C84’. In order to determine the genetics of the resistance of the durum wheat cultivar ‘Jupare C2001’ resistant to the leaf rust race that overcome the ‘Altar C84’ resistance, and to determine if ‘Jupare C2001’ carries Lr14a, ‘Jupare C2001’ was crossed with ‘Altar C84’ and ‘Altar C84’+Lr14a. The response of Lr14a to the infection of leaf rust in seedlings to races BBG/BN and BCG/BN which are virulent to ‘Altar C84’ is heterogeneous whit large urenidiums (X to X+ in the 0-4 scale) in both bread and durum ‘Altar C84’ background. In adult plant stage to the same races, Lr14a confers near immunity. For better and effective expression of the resistance that Lr14a gene confers against the leaf rust races preferably attacking bread wheat,  In order to determine the genetics of the resistance of the durum wheat cultivar ‘Jupare C2001’ resistant to the leaf rust race that overcome the ‘Altar C84’ resistance, and to determine if ‘Jupare C2001’ carries Lr14a, ‘Jupare C2001’ was crossed with ‘Altar C84’ and ‘Altar C84’+Lr14a. The response of Lr14a to the infection of leaf rust in seedlings to races BBG/BN and BCG/BN which are virulent to ‘Altar C84’ is heterogeneous whit large urenidiums (X to X+ in the 0-4 scale) in both bread and durum ‘Altar C84’ background. In adult plant stage to the same races, Lr14a confers near immunity. For better and effective expression of the resistance that Lr14a gene confers against the leaf rust races preferably attacking bread wheat, is necessary the ‘Altar C84’ gene.

Nele Verhulst, Bram Govaerts

Part B — User guide

Bram Govaerts, Nele Verhulst