Alejandro Zamora
Graduate Student
153 Biotechnology Building
Cornell University
Ithaca, New York 14853-2703
Tel: 607 254-6753
Fax: 607 255-6249
e-mail: az42@cornell.edu
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My research at Cornell has involved the dissection of the genomic elements that determine the adaptive and economically essential characteristic of increased disease resistance, and in understanding the mechanisms involved in the evolution of these genes, and the genome structure itself, that lead to this resistance. This in turn should allow for the design of better plant breeding strategies that use the diversity found in genetic resources more efficiently and lead to more rapid development of substantially improved plant varieties.
My investigation is based in the new paradigm that landraces and wild germplasm accessions hold in their genomes a treasure trove of genetic resources useful for breeding including disease resistance alleles, adaptation to difficult and changing environments and better quality in terms of nutrients and thus taste. Therefore, a good part of my research has dealt with elucidating the mechanisms that allow plants withstand the selective pressure imposed by the multitude of potentially pathogenic microorganisms, and more specifically the threat of anthracnose. Some of the questions I have addressed include: What are the genes involved in the molecular interaction between sorghum and the anthracnose fungus Colletotrichum sublineolum? Which of these are unique to sorghum and which are found also in other species of cereals, especially in the closely related commodities sugarcane and corn? Is there evidence of adaptive evolution in the sets of orthologous genes from different cereal species? And finally, is there evidence of recent selective events in current populations?
To explore for answers to these questions I have used a reverse genetics approach, based on the expression profile of thousands of sorghum genes, and then used comparative genomics to identify those genes that are not only highly upregulated as a consequence of inoculation with the pathogen, but that are also divergent as a result of recurrent events of positive selection. These divergent and positively selected genes can be functionally essential in terms of disease resistance, therefore their identification is a first step leading to the selection of functionally useful polymorphisms from the germplasm and to the improvement of cultivars via marker assisted selection or genetic engineering with modified versions of these genes. I’m currently writing two scientific articles intended for peer-reviewed journals detailing the results of my research done during my Ph.D.
Some questions that I’d like to address in the future include : What was the origin of these genes and how have they evolved? What is the effect of particular alleles and genotypic combinations for the loci analyzed in the susceptible/resistant phenotype?
My M.Sc. thesis dealt with the identification and characterization of native genetic resources of rice in Costa Rica. It involved two years of intensive field work collecting rice plants from rivers, marshes and swamps, all over Costa Rica and later the morphological description, taxonomic analysis and a population genetic structure analysis of one of the species. Doing this work I become conscious of the great diversity of genetic resources, both in terms of species and genetic diversity within species, that is available not only of rice, but for many other crop species and became very interested in the value of these genetic resources in breeding, particularly for disease resistance. I decided at this point to learn how to use and preserve them appropriately, which is why I came to Cornell.