Propane Dehydrogenation Using Transition Metal Cluster Catalysts

Our research seeks to determine the propane dehydrogenation (PDH) reaction pathways using various transition-metal cluster catalysts. We are studying the first step of the reaction, in which a C-H bond is broken. This has been previously shown to be the rate-limiting step of the PDH reaction. We are calculating the PDH activation energy (Ea) using the Vienna Ab-Initio Simulation Package (VASP) in conjunction with the nudged elastic band algorithm. Thus far, we have studied Pt, Ta, and Ni clusters ranging in size from 2-10 atoms. Our goal is to better understand the dependence of Ea on metal type and cluster size

The Center of Excellence in Genomics (CEG) for enhancing the utilization of molecular tools in breeding and research

ICRISAT has partnered with the Department of Biotechnology (DBT), Government of India, to establish the Center of Excellence in Genomics (CEG) at ICRISAT with financial support from the DBT. The CEG was launched through an exchange of a Memorandum of Agreement (MoA) signed by Dr William Dar, Director General of ICRISAT and Dr MK Bhan, Secretary of DBT on 13 December 2006 at a function organized at ICRISAT headquarters at Patancheru, India (see photo)

Research and field monitoring on transgenic crops by the Centro Internacional de Mejoramiento de Maíz y Trigo (CIMMYT)

The International Maize and Wheat Improvement centre (CIMMYT) aims to genetically enhance both crops and generate public sector-provided products for the resource poor, e.g., drought tolerant wheat and insect resistant maize, and through international-national partnerships facilitate the acquisition of improved germplasm for non-mandate crops in the cropping systems where maize and wheat thrives; e.g., GM-papaya through a national food security undertaking in Bangladesh. The centre also engages in public awareness campaigns in projects such as Insect Resistance Maize for Africa (IRMA), which includes food, feed and environmental safety, monitoring of resistance and establishment of refugia, non-target effects and gene flow. Monitoring of genetic resources is a wide concern among the centres of the Consultative Group on International Agricultural Research (CGIAR), with an emphasis on the quality of gene banks. Decisions, policies and procedures about monitoring should be science-based, and this requires education, an area where CIMMYT and other CGIAR centres can play an important role. There will be a need to continue to evaluate the need for, and type of monitoring, as new (and unique) products are developed and released in the emergent economies of the world

Peanut improvement: production of fertile hybrids and backcross progeny between Arachis hypogaea and A. kretschmeri

There are only a few reports of successful crosses between cultivated peanut (Arachis hypogaea L., section Arachis) and wild species from sections other than section Arachis. Many of the wild Arachis species harbor important traits necessary for the improvement of peanut. For example, Arachis kretschmeri Krapov., W.C. Gregory & C.E. Simpson (section Procumbentes) can grow under water-logged conditions and has been identified as one of the few wild species of Arachis with resistance to late leaf spot (LLS) and peanut rosette disease. Peanut rosette, caused by a combination of viruses, is an economically important disease only in Africa, while LLS, caused by Cercosporidium personatum, is an important fungal disease in Asia and the Americas as well as Africa. Interspecific hybrids between A. hypogaea and A. kretschmeri were produced by applying growth regulators to pollinated pistils and hybrid plants were obtained by germinating embryos in vitro. A total of seven hybrids were produced and confirmed by Simple Sequence Repeat (SSR) analysis. All hybrids were fertile, although initially slow growing. F1 hybrids were backcrossed to A. hypogaea and all plants in the F1BC1 generation were single-seeded with a prominent beak, characteristic of A. kretschmeri, but many of the F1BC2 pods were double-seeded resembling A. hypogaea. F1BC2 plants were moderately resistant to LLS. When a large number of seeds are obtained, the progeny will be screened for resistance to both LLS and rosette disease. Thus crosses with species outside the section Arachis may not only confer disease resistance but will also broaden the genetic base of cultivated peanut

Molecular markers for plant breeding: comparisons of RFLP and RAPD genotyping costs

Three molecular marker protocols, chemiluminescent restriction fragment length polymorphisms (c-RFLPs), radioactivity-based restriction fragment length polymorphisms (r-RFLPs), and randomly amplified DNA polymorphisms (RAPDs) were compared in terms of cost and time efficiency. Estimates of cost of supplies and time requirements were obtained from simulations of maize (Zea mays L.) genotyping experiments utilizing protocols currently in use. The increase in total cost with increasing numbers of individuals genotyped and markers analyzed is higher for RAPDs than for RFLPs. RAPDs were generally found to be more cost and time efficient for studies involving small sample sizes, while RFLPs have the advantage for larger sample sizes. Because of the shorter exposure times involved, c-RFLPs require less time than r-RFLPs to obtain a given amount of information. Variations in the protocols, such as number of re-uses of Southern blots or cost of Taq DNA polymerase per reaction of amplification, also affect the relative merits of RAPDs and RFLPs. Two examples were analyzed where molecular markers are used: a germ plasm survey and quantitative trait loci (QTL) mapping in a segregating population. No protocol was found to be the most cost and time efficient over the entire range of sample sizes and number of marker loci studied

Efficacy and Deployment of Transgenic Plants for Stemborer Management

Transgenic plants expressing Bacillus thuringiensis δ-endotoxins are now being used commercially in several crop species. These toxins have demonstrated good control of temperate (Ostrinia nubilalis) and tropical (Diatraea grandiosella and D. saccharalis) stemborers in maize. Resistance to B. thuringiensis toxins has been reported in over 11 species in both field and laboratory studies, demonstrating the need for resistance management strategies to prolong the efficacy of this valuable pest management tool within an integrated control programme. Resistance involves reduced binding of toxins to midgut epithelial cells and is generally considered to be a recessive trait. Resistance management will require the use of spatial and temporal refugia which may require unique schemes for each pest complex. Information is presented on the mode of action of cry toxins, resistance mechanisms, interaction of transgenic plants and biocontrol agents, and management/deployment strategies for transgenic maize in tropical ecologies

Marker-assisted selection: new tools and strategies

The development of molecular genetics and associated technology has facilitated a quantum leap in our understanding of the underlying genetics of the traits sought through plant breeding. The usefulness of DNA markers for germplasm characterization, and of marker-assisted selection—the manipulation through DNA markers of genomic regions that are involved in the expression of traits of interest—for single-gene transfer, has been well demonstrated. However, when several genomic regions must be manipulated, marker-assisted selection has turned out to be less useful. The efficient and effective application of marker-assisted selection for polygenic trait improvement certainly needs new technology but, more importantly, it requires the development of innovative strategies that bypass the conceptual bottlenecks imposed by current approaches

Genetic mapping of maize streak virus resistance from the Mascarene source. II. Resistance in line CIRAD390 and stability across germplasm

The streak disease has a major effect on maize in sub-Saharan Africa. Various genetic factors for resistance to the virus have been identified and mapped in several populations; these factors derive from different sources of resistance. We have focused on the Réunion island source and have recently identified several factors in the D211 line. A second very resistant line, CIRAD390, was crossed to the same susceptible parent, B73. The linkage map comprised 124 RFLP markers, of which 79 were common with the D211×B73 map. A row-column design was used to evaluate the resistance to maize streak virus (MSV) of 191 F2:3 families under artificial infestation at two locations: Harare (Zimbabwe) and in Réunion island. Weekly ratings of resistance were taken and disease incidence and severity calculated. QTL analyses were conducted for each scoring date and for the integration over time of the disease scores, of incidence, and of severity. Heritability estimates (71–98%) were as high as for the D211×B73 population. Eight QTLs were detected on chromosomes 1, 2, 3, 5 (two QTLs), 6, 8, and 10. The chr1-QTL explained the highest proportion of phenotypic variation, about 45%. The QTLs on chromosomes 1, 2, and 10 were located in the same chromosomal bin as QTLs for MSV resistance in the D211×B73 population. In a simultaneous fit, QTLs explained together 43–67% of the phenotypic variation. The QTLs on chromosomes 3, 5, and 6 appeared to be specific for one or the other component of the resistance. For the chr3-QTL, resistance was contributed by the susceptible parent. There were significant QTL × environment interactions for some of the variables studied, but QTLs were stable in the two environments. They also appeared to be stable over time. Global gene action ranged from partial dominance to overdominance, except for disease severity. Some additional putative QTLs were also detected. The major QTL on chromosome 1 seemed to be common to the other sources of resistance, namely Tzi4, a tolerant line from IITA, and CML202 from CIMMYT. However, the distribution of the other QTLs within the genome revealed differences in Réunion germplasm and across these other resistance sources. This diversity is of great importance when considering the durability of the resistance

Propane Dehydrogenation Using Transition Metal Cluster Catalysts

Our research seeks to determine the propane dehydrogenation (PDH) reaction pathways using various transition-metal cluster catalysts. We are studying the first step of the reaction, in which a C-H bond is broken. This has been previously shown to be the rate-limiting step of the PDH reaction. We are calculating the PDH activation energy (Ea) using the Vienna Ab-Initio Simulation Package (VASP) in conjunction with the nudged elastic band algorithm. Thus far, we have studied Pt, Ta, and Ni clusters ranging in size from 2-10 atoms. Our goal is to better understand the dependence of Ea on metal type and cluster size

Genetic mapping of maize streak virus resistance from the Mascarene source. I. Resistance in line D211 and stability against different virus clones

Maize streak virus (MSV) disease may cause significant grain yield reductions in maize in Africa. Réunion island maize germplasm is a proven source of strong resistance. Its genetic control was investigated using 123 RFLP markers in an F2 population of D211 (resistant) × B73 (susceptible). This population of 165 F2:3 families was carefully evaluated in Harare (Zimbabwe) and in Réunion. Artificial infestation was done with viruliferous leafhoppers. Each plant was rated weekly six times after infestation on a 1–9 scale previously adjusted by image analysis. QTL analyses were conducted for each scoring date, and for the areas under the disease, incidence and severity progress curves. The composite interval mapping method used allowed the estimation of the additive and dominance effects and QTL × environment interactions. Heritabilities ranged from 73% to 98%, increasing with time after infestation. Resistance to streak virus in D211 was provided by one region on chromosome 1, with a major effect, and four other regions on chromosomes 2, 3 (two regions) and 10, with moderate or minor effects. Overall, they explained 48–62% of the phenotypic variation for the different variables. On chromosome 3, one of the two regions seemed to be more involved in early resistance, whereas the second was detected at the latest scoring date. Other QTLs were found to be stable over time and across environments. Mild QTL × environment interactions were detected. Global gene action appeared to be partially dominant, in favor of resistance, except at the earliest scoring dates, where it was additive. From this population, 32 families were chosen, representing the whole range of susceptibility to MSV. They were tested in Réunion against three MSV clones, along with a co-inoculation of two of them. Virulence differences between clones were significant. There were genotype × clone interactions, and these were more marked for disease incidence than for severity. Although these interactions were not significant for the mean disease scores, it is suggested that breeders should select for completely resistant genotypes