Submitted to: Cucurbit Genetics Cooperative Report
Publication Type: Research Notes
Publication Acceptance Date: November 30, 2001
Publication Date: N/A
Interpretive Summary: Molecular marker analysis is a tool that has been derived from the modern biotechnological revolution. Molecular markers are made from DNA (a substance that resides in every cell that is the basis of life) that is used as place markers on the chromosome (single units of DNA that contain genes) to marker the location of genes (the points on the chromosome that provide differences between individuals). Molecular markers associated with melon DNA were identified in this study. For these molecular markers to be useful in genetics studies, their mode of inheritance (the way they are passed from parent to offspring) must be known. This study was designed to determine the genetic inheritance of 195 molecular markers in melon. This information allows the scientist working melon to use these molecular markers for genetic analyses. These genetic analyses allow for a more precise description of the DNA differences between melon plants. If these differences are known, the melon breeder can more creatively use the knowledge to develop better strains of melons.
Technical Abstract: Genetic markers have been employed in diversity analysis and the construction of maps in melon. The use of random amplified polymorphic DNA (RAPD) has allowed for discrimination of elite and unadapted germplasm. Because of their relative low cost and low technological attributes they have been valuable for diversity analysis. However, except for the mapping of several RAPD marker loci by Baudracco-Arnas and Pitrat in 1996, the genetics RAPD markers in melon has not been widely characterized. This is likely due to the relatively low level of RAPD polymorphisms (approx 15-20 percent) in melon. The bands used for diversity analysis are repeatable, but their genetic attributes have not been characterized. This report details the genetics of RAPD markers assessed in F2 progeny segregating in four melon populations (crosses). The primers examined yielded between 25 to 40 percent polymorphisms (band differences between parents) depending on the cross. Potentially useful bands were characterized as having a mobility between 200 to 2,500 bp. Putative loci were then identified as those possessing bands that were reproducible and bright and used for segregation analysis. On average, there was a 17 percent recovery of potentially useable bands (loci) from the survey of 1,500 primers. Based on segregation analysis (3:1 ratio), 195 loci were identified (about 3.3 percent recovery on average). The loci characterized in this study can be used by geneticists for genomic mapping and genetic analyses. If a tight linkage is found (less than 5cM), then marker-trait associations can increase breeding efficiency. The characterization of these markers makes them available to germplasm curators for genetic analyses of populations.