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  • Author or Editor: James P. Prince x
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Pepper (Capsicum spp.) has the same basic chromosome number as tomato and other solanaceous plant species (2n = 2x = 24). By using the probes mostly from a tomato map, we have generated three molecular maps of pepper from interspecific F2 crosses of C. frutescens BG 2814-6, C. chinense PI 159234 and C. annuum `NuMex RNaky' with restriction fragment length polymorphisms, isozymes, random amplified polymorphic DNAs, and morphological traits. The best developed map is from C. annuum × C. chinense F2 cross, which currently has 366 markers covered 1081 cM in 18 linkage groups. Three linkage groups were assigned to three chromosomes based on primary trisomics. Several disease resistance genes including monogenic resistance to potyviruses and quantitative trait loci for resistance to tobacco mosaic virus and cucumber mosaic virus have been mapped. The distribution of allele frequency and marker segregation ratios have been analyzed. Chi-square analyses of all clones showed more skewing of segregation ratios in C. annuum × C. chinense population than the other two populations. The skewing occurs throughout the genome and tends towards heterozygote and one of the parents. The order of markers among three pepper maps will be compared and the comparisons of synteny between pepper and tomato maps will be described. A composite of three pepper maps will be presented using JoinMap software.

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Garlic has been propagated exclusively by asexual means since time immemorial. The recent discovery of male fertile garlic accessions allowed studies on genetics and garlic improvement. Single nucleotide polymorphism (SNP) and random amplified polymorphic DNA (RAPD) based genetic linkage map was developed for garlic using a segregating population derived from one plant of PI 540316. Progenies segregated for male fertility and other morphological characters. Distortion of segregation was observed for most of the markers. This was expected due to the segregation of recessive deleterious alleles present in the garlic genome. The map contained 23 loci distributed on five linkage groups. It covered 319 cM with the average of 18 cM between loci. Linkage with the male fertility (Mf) locus was established with SNP marker AOB155 (26.7 cM).

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Garlic (Allium sativum L.) has been cultivated by asexual propagation since time immemorial. The discovery of male-fertile garlic accessions has opened a venue for genetic studies and improvement through sexual recombination. An S1 family of 84 plants was generated from a single male-fertile heterozygous plant from the U.S. Dept. of Agriculture Plant Introduction 540316 and used to identify the first genetic linkages in garlic based on single nucleotide polymorphisms, simple sequence repeats, and randomly amplified polymorphic DNAs. Thirty-seven markers formed nine linkage groups covering 415 centimorgans (cM) with average distance of 15 cM between loci; other 16 loci remained unlinked. A male fertility locus was placed on the map. This first genetic map of garlic is a seminal step toward the genetic improvement of garlic and eventual marker-assisted breeding.

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