Application of multivariate analysis to electrical penetration graphs using manual and automate waveform recognization from the planthopper Peregrinus maidis feeding on susceptible and resistant maize

The stylet penetration activities of Peregrinus maidis (Ashmead) (Homoptera: Delphacidae), vector of Maize mosaic virus (MMV) and Maize stripe virus (MStV) were studied by electrical penetration graphs (DC-EPG) on resistant and susceptible maize inbred lines. Multivariate analyses were applied to two sets of data obtained by manual and automated methods of waveform recognition from digital EPG recordings. For both methods, the variables, which mostly explained the resistance-susceptibility status of the maize lines, appeared to be related to the passive ingestion in phloem vessel and stylet pathway and to a lesser extent to active ingestion in xylem and to non-penetration. In spite of a great variability within each plant genotype, plants could be divided in three classes, susceptible, slightly resistant and resistant to the virus transmission. These results are discussed in relation to the possible mechanism of maize resistance to P. maidis and the usefulness of automated waveform recognition with the software "EPG soft" for plant breeding. (Résumé d'auteur

A method to search for optimal field allocations of transgenic maize in the context of co-existence

Spatially isolating genetically modified (GM) maize fields from non-GM maize fields is a robust on-farm measure to keep the adventitious presence of GM material in the harvest of neighboring fields due to cross-fertilizations below the European labeling threshold of 0.9%. However, the implementation of mandatory and rigid isolation perimeters can affect the farmers' freedom of choice to grow GM maize on their fields if neighboring farmers do not concur with their respective cropping intentions and crop plans. To minimize the presence of non-GM maize within isolation perimeters implemented around GM maize fields, a method was developed for optimally allocating GM maize to a particular set of fields. Using a Geographic Information System dataset and Monte Carlo analyses, three scenarios were tested in a maize cultivation area with a low maize share in Flanders (Belgium). It was assumed that some farmers would act in collaboration by sharing the allocation of all their arable land for the cultivation of GM maize. From the large number of possible allocations of GM maize to any field of the shared pool of arable land, the best field combinations were selected. Compared to a random allocation of GM maize, the best field combinations made it possible to reduce spatial co-existence problems, since at least two times less non-GM maize fields and their corresponding farmers occurred within the implemented isolation perimeters. In the selected field sets, the mean field size was always larger than the mean field size of the common pool of arable land. These preliminary data confirm that the optimal allocation of GM maize over the landscape might theoretically be a valuable option to facilitate the implementation of rigid isolation perimeters imposed by law.

Ontology-driven International Maize Information System (IMIS) for Phenotypic and Genotypic Data Exchange

The Consultative Group on International Agricultural Research (CGIAR; http://www.cgiar.org/) centres have developed the International Crop Information System (ICIS; http://www.icis.cgiar.org) for the management and integration of global information on genetic resources, and germplasm improvement for any crop. The Maize breeding programs at CIMMYT (http://beta.cimmyt.org/) have different software tools to manage phenotypic, genotypic, and environmental information for their experiments generated worldwide. These tools have the capacity of collecting information in the field, wet lab, and store it into different relational databases. The IMIS (http://imis.cimmyt.org/confluence/display/IMIS/Crop+Finder) is an implementation of the ICIS, which is a computerized database system for general, integrated management and utilization of genealogy, nomenclature, genetic, phenotypic and characterization data for maize. Data exchange within and between databases as well as retrieving information are often hampered by the variability of terms used to describe comparable objects. To overcome this problem, the Crop Ontology (CO) database (http://cropontology.org/) is developed. It provides controlled vocabulary sets for several economically important plant species and facilitates biocurators working in genebanks of plant genetic resources (PGR) and crop breeding data curation and annotation. The maize trait ontology is developed as one of subclasses of CO trait ontology providing standardized trait descriptions, scales and scale values implemented into the IMIS. This ontology-driven IMIS will allow researchers who wish to exploit comparative phenotypic and genotypic information of maize to elucidate functional aspects of each trait

Framework and Initial Analyses of Fertilizer Profitability in Maize and Cotton in Zambia

Inorganic fertilizers will play a role in government programs, but whether or not a single policy is valuable for all farmers depends upon the net gain for the farmers. The research here seeks to demonstrate how to answer the question “Is fertilizer profitable in Zambia for maize and cotton in the smallholder sector?” This study identifies the key components determining profitability and then sets up a framework to evaluate the probability of farmers to obtain profitable results with fertilizer use on maize and cotton. Several cases are selected and the results are evaluated. Private profitability for the farmer at market prices is discussed, leaving social profitability to other researchers. A simple method for farmers and extensionists to use to assess a fertilizer investment is given, to assist in more site specific analysis, given prices and environment.food security, food policy, Zambia, maize, cotton, fertilizer, Agribusiness, Q18,

The Maize Seed Industries of Brazil and Mexico: Past Performance, Current Issues, and Future Prospects

This paper describes results of a study of the main factors affecting the development of the maize seed industries in Brazil and Mexico (and, by extension, other developing countries). The authors develop a framework that researchers and policy makers can use to evaluate seed industry performance in developing countries. This framework is used to analyze the seed industries of Brazil and Mexico, where very different sets of circumstances influence seed industry development, efficiency, and structure. The analysis gives special attention to the different maize breeding strategies pursued by the public and private sectors, measures of industry competitiveness and efficiency, and the trade-offs involved in developing and producing different kinds of maize seed, particularly improved open-pollinated maize varieties versus different types of hybrids. The authors identify key seed industry issues for researchers, administrators of national maize programs, and agricultural policy makers in developing countries, especially issues related to the appropriate roles for public and private organizations in maize seed industries in the developing world.Crop Production/Industries,

Comparing Yields and Profitability in MARD's High- and Low-Input Maize Programs 1997/98 Survey Results and Analysis

This paper summarizes the results from data collected during the study’s second year, 1997/98. The analysis is based on a sample of 210 smallholder farmers in Nampula Province using three different sets of production practices: the DNER/Sasakawa- Global 2000 Program (DNER/SG) high-input package (improved open-pollinated maize, 100 kg/ha each 12-24-12 and urea fertilizer on credit); improved planting and weeding practices only (using local seed, without fertilizer); and a control group of farmers using traditional practices (no improved seed or fertilizer). The objectives of the research were to: describe the characteristics, input use patterns and yield response by group; analyze the relative contribution to yield of the different technologies, environmental factors, and management practices; and assess the profitability of the three different technology types at the farm level.food security, food policy, Mozambique, maize, Crop Production/Industries, Q18,

Correlation analysis of the transcriptome of growing leaves with mature leaf parameters in a maize RIL population

Background: To sustain the global requirements for food and renewable resources, unraveling the molecular networks underlying plant growth is becoming pivotal. Although several approaches to identify genes and networks involved in final organ size have been proven successful, our understanding remains fragmentary. Results: Here, we assessed variation in 103 lines of the Zea mays B73xH99 RIL population for a set of final leaf size and whole shoot traits at the seedling stage, complemented with measurements capturing growth dynamics, and cellular measurements. Most traits correlated well with the size of the division zone, implying that the molecular basis of final leaf size is already defined in dividing cells of growing leaves. Therefore, we searched for association between the transcriptional variation in dividing cells of the growing leaf and final leaf size and seedling biomass, allowing us to identify genes and processes correlated with the specific traits. A number of these genes have a known function in leaf development. Additionally, we illustrated that two independent mechanisms contribute to final leaf size, maximal growth rate and the duration of growth. Conclusions: Untangling complex traits such as leaf size by applying in-depth phenotyping allows us to define the relative contributions of the components and their mutual associations, facilitating dissection of the biological processes and regulatory networks underneath

Comparison of drought stress response and gene expression between a GM maize variety and a near-isogenic non-GM variety

Maize MON810, grown and commercialised worldwide, is the only cultivated GM event in the EU. Maize MON810, variety DKC6575, and the corresponding near-isogenic line Tietar were studied in different growth conditions, to compare their behaviour in response to drought. Main photosynthetic parameters were significantly affected by water stress in both GM and non –GM varieties to a similar extents. Though DKC6575 (GM) had a greater sensitivity in the early phase of stress response as compared with Tietar (non GM), after six days of stress they behaved similarly, and both varieties recovered from stress damage. Profiling gene expression in water deficit regimes and in a generalised water stress condition showed an up-regulation of many stress- responsive genes, but a greater number of differentially expressed genes was observed in Tietar, with genes belonging to transcription factor families and genes encoding HSPs, LEAs and detoxification enzymes. Since induction of these genes have been indicated from the literature as typical of stress responses, their activation in Tietar rather than in DKC6575 may be reminiscent of a more efficient response to drought. DKC6575 was also analysed for the expression of the transgene CryIAb (encoding the delta-endotoxin insecticidal protein) in water deficit conditions. In all the experiments, the CryIAb transcript was not influenced by water stress, but was expressed at a constant level.. This suggests that though possessing a different pattern of sensitivity to stress, the GM variety maintains the same expression level for the transgene