Project Number: 5320-21000-010-00
Project Type: Appropriated

Start Date: Sep 27, 2003
End Date: Sep 26, 2008

Objective:
Produce new knowledge about the molecular biology & genetics of selected tropical crop plants. Analyze genomic structures to identify markers linked to important agronomic traits. Improve germplasm through genetic transformation for increased resistance to pathogens & pests. Determine the genomic structure of, and identify markers linked to important agronomic traits in selected tropical crop plants. Develop improved germplasm with increased resistance to pathogens and pests through genetic transformation. Develop transgene constructs that mitigate potential environmental and biosafety risks of transgenic plants. Assess the potential environmental and biosafety risks of transgenic plants. Develop approaches for managing risks of transgenic plants. Assess the potential commercial application of transgenic plants that are developed. Improve control of transgene expression & create tissue specific & other desired patterns of expression by developing new gene promoters. Identify and characterize regulatory controls over metabolism to improve quality & yield.

Approach:
Cross lines of papaya to produce families segregating for important agronomic traits and for mapping of extracted DNA with molecular markers. DNA analysis will be based on a variety of techniques to characterize genetic diversity and to identify markers co-segregating with phenotype characters to assist breeders in marker assisted selection. Tissue cultures will be genetically transformed with available and newly developed gene constructs. Risk mitigating gene constructs that consists of short-linked segments of genes or computer-generated consensus sequences derived from sequences of a family of genes or gene segments will be developed. Tissue cultures will be genetically transformed with borrowed and developed gene constructs then regenerated into plants for evaluation for resistance to pathogens and enhanced agronomic traits. Promising transgenic lines will be evaluated for potential environmental and biosafety risks under laboratory, greenhouse, field, and simulated commercial conditions. Farming and cultural practices combined with transgenic constructs will be evaluated for managing the risks of viral strains that may arise from recombination of attacking viruses and transgenes. Gene expression will be studied as a function of promoter and enhancer elements engineered for site-specific integration and tissue-specific expression. Genes for altering metabolism will be used in transformation in attempts to improve specific yield and quality parameters of the crops. FY03 Program Increase $178,830. Formerly 5320-21000-008-00D (9/03). FY04 Program Increase $322,088.