A F[sub 2] linkage map of Pisum sativum L. based on both classical and molecular genetic markers
Nelson, Jeffery A.
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Linkage maps are often compiled from the analysis of many different crosses. With the advent of molecular genetic markers such as RFLPs and, more recently, RAPDs, it has become possible to generate an extensive linkage map through the analysis of a single cross. This project utilizes a single reciprocal F2 cross between two pea inbred lines (A1078-234 and PI 179449) to integrate a combination of classical Mendelian and modern molecular characters (morphological traits, isozymes, RFLPs [restriction fragment length polymorphisms] and a large number of newly generated RAPDs [random amplified polymorphic DNA]). To develop the RAPD data set efficiently, primer surveys were first performed to detect variation between the two parental lines. Primers producing polymorphisms were then used to scan 56 F2 progeny. After 100 RAPD bands were obtained, bulk segregant analysis was used to find the precise location of four previously unassigned phytochromeregulated genetic loci (denoted Pea25, Pea207, Pea2l5 and Pea315). The resulting data were analyzed by multipoint linkage analysis using the MAPMAKER computer program. One hundred twenty-nine markers were placed on the seven linkage groups of pea: 40 dominant markers derived from the A1078-234 parent ("A" characters), 72 dominant markers derived from the PI 179449 parent ("P" characters), and 17 codominant markers. All linkage groups have "A," "P," and codominant characters except I and VI, which have only "P" characters and a codominant marker. There are also nine unlinked blocks that include a total of 35 markers: two codominant characters and 33 RAPDs. Bulk segregant analysis provided evidence that Pea207 and Pea 315 reside in linkage groups II and III, respectively. The RAPDs also confirmed a rearrangement between linkage groups I and II Although several RAPDs were linked with the Pea25 Pea215 linkage block through bulk segregant analysis, the block needs to be extended further to be incorporated in the map. Given the fact that linkage groups I and IV have been assigned relatively few markers to date, the Pea25/Pea215 linkage block may well reside at one of these two locations. Based on bulk segregant survey results and the rearrangement of linkage groups I and II, the most likely first choice of assignment for the Pea 25/Pea215 linkage segment is linkage group I