Search Results
The population structure and genetic diversity of American chestnut trees collected in nine states along the natural range of the species was evaluated using 20 isozyme loci. Genetic heterozygosity (Ht:Nei, 1978) ranged from 0.089 in the Georgia and 0.094 in the North Carolina population to 0.172 in the northernmost (Connecticut) and 0.181 in the southernmost (Alabama) population. Four populations (Pennsylvania, New York, Virginia, and Alabama) were selected for RAPD analysis using 22 loci randomly distributed across the chestnut genome. The highest level of heterozygosity was in the Alabama population. UPGMA phenograms generated for the isozyme and RAPD markers using Nei's genetic identity showed similar genetic relationships among American chestnut populations.
A linkage map was constructed of the watermelon genome using F2 and F2:3 populations segregating for resistance to race 1 and 2 of Fusarium oxysporum f. sp. niveum (FON 1 and 2). Sixty-four percent of the RAPD primers used in the parents and F1 detected polymorphism. In the F2, 143 polymorphic bands were scored, 60% of which exhibited the expected 3:1 segregation ratio. A 113 cM linkage map was constructed using Mapmaker version 3 and LOD of 4. DNA pools of Fusarium wilt resistant or susceptible F2:3 lines were created and bulked segregant analysis was used to detect molecular markers linked to FON 1 or FON 2 resistance. Four individuals per line were used to confirm linkages and construct an F2:3 linkage map. One large linkage group was detected in both generations. A large proportion of the RAPD and SSR markers were unlinked and many showed segregation distortion. Single-factor ANOVA for each pairwise combination of marker locus and resistance or morphological trait was conducted. RAPD markers with putative linkages to FON 1 and FON 2 and several morphological traits were detected.