A tetraploid F 2 progeny segregating for resistance to black spot, growth habit, and absence of prickles on the stem and petioles was used to construct genetic linkage maps of rose. The F 1 of the progeny, 90-69, was created by crossing a black spot-resistant amphidiploid, 86-7, with a susceptible tetraploid, 82-1134. The F 1 was open-pollinated to obtain 115 seedlings. AFLP and SSR markers were used to eliminate seedlings produced through cross-fertilization. The remaining progeny set of 52 F 2 plants was used to study the inheritance of 675 AFLPs, one isozyme, three morphological and six SSR markers. AFLP markers were developed with three combinations of restriction enzymes, EcoRI/MseI, KpnI/MseI and PstI/MseI. Most of the markers appear to be in simplex or single-dose and segregated 3:1 in the progeny. One linkage map was constructed for each parent using only the single-dose markers. The map of 86-7 consists of 171 markers assigned to 15 linkage groups and covering more than 902 cM of the genome. The map of 82-1134 consists of 167 markers assigned to 14 linkage groups and covering more than 682 cM of the genome. In the AFLP analysis, EcoRI/MseI generated nearly twice as many markers per run than PstI/MseI. Markers developed with three restriction enzyme combinations showed a mixed distribution throughout the maps. A gene controlling the prickles on the petiole was located at the end of linkage group 7 on the map of 86-7. A gene for malate dehydrogenase locus 2 was located in the middle of linkage group 4 on the map of 86-7. These first-generation maps provide initial tools for markerassisted selection and gene introgression for the improvement of modern tetraploid roses.
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. ABSTRACTField observations, chromosome counts, flavonoid chemistry, breeding system data, hybridization experiments, and a quantitative analysis of twelve morphological features combine to show that the North and Central American populations of B. pilosa sensu Sherif actually include three distinct species: B. odorata (n = 12), B. alba (n = 24), and B. pilosa (n = 36). All these taxa are square-stemmed, white-rayed or discoid annuals with linear, obcompressed-quadrangulate achenes, but each species can be distinguished morphologically by differences in ray length and width, in outer phyllary length, width and shape and chemically by differences in the chalcones accumulated in their leaves. New combinations are proposed and two varieties, B. odorata var. oaxacensis and B. odorata var. chilpancingensis, are described as new. Descriptions, distribution maps, synonymies, and a key to all taxa are provided. BIDENS PILOSA L. (Asteraceae) is a widely distributed subtropical and tropical weed with its center of diversification in Mexico.Throughout its range, this taxon is recognized by its annual habit, square stem, and linear, obcompressed-quadrangulate, attenuate achenes. However, many characters within this taxon are highly variable. For example, the plants may be erect or decumbent; leaflets may be simple, tripartite, or highly dissected; heads may be discoid or radiate, if radiate the rayflorets may be white, yellowish or roseus; the ray-florets may be minute (2-4 mm) to long (15-20 mm); and the achenes may be awnless or 2-5 awned.Sherff (1937) used these morphological characters to separate B. pilosa into six varieties: var. pilosa, var. minor, var. radiata, var. bimucronata, var. calcicola, and var. alausensis. The most widely distributed varieties, var. pilosa and var. minor, are cosmopolitan throughout tropical and subtropical regions. The other four varieties have a more narrow geographic range, occurring primarily in the Western Hemisphere. The habitats these varieties occupy range from disturbed regions on dry or moist mountains and high mountain plateaus and valleys to tropical lowlands.Since Sherffs taxonomic treatments are based primarily on herbarium specimens, he did not realize that many of these morphological vari-
We have constructed a genetic linkage map of peach [Prunus persica (L.) Batsch] consisting of RFLP, RAPD and morphological markers, based on 71 F2 individuals derived from the self-fertilization of four F1 individuals of a cross between 'New Jersey Pillar' and KV 77119. This progeny, designated as the West Virginia (WV) family, segregates for genes controlling canopy shape, fruit flesh color, and flower petal color, size and number. The segregation of 65 markers, comprising 46 RFLP loci, 12 RAPD loci and seven morphological loci, was analyzed. Low-copy genomic and cDNA probes were used in the RFLP analysis. The current genetic map for the WV family contains 47 markers assigned to eight linkage groups covering 332 centi Morgans (cM) of the peach nuclear genome. The average distance between two adjacent markers is 8 cM. Linkage was detected between Pillar (Pi) and double flowers (Dl) RFLP markers linked to Pi and flesh color (γ) loci were also found. Eighteen markers remain unassigned. The individuals analyzed for linkage were not a random sample of all F2 trees, as an excess of pillar trees were chosen for analysis. Because of this, Pi and eight other markers that deviated significantly from the expected Mendelian ratios (e.g., 1∶2∶1 or 3∶1) were not eliminated from the linkage analysis. Genomic clones that detect RFLPs in the WV family also detect significant levels of polymorphism among the 34 peach cultivars examined. Unique fingerprint patterns were created for all the cultivars using only six clones detecting nine RFLP fragments. This suggests that RFLP markers from the WV family have a high probability of being polymorphic in crosses generated with other peach cultivars, making them ideal for anchor loci. This possibility was examined by testing RFLP markers developed with the WV family in three other unrelated peach families. In each of these three peach families respectively 43%, 54% and 36% of RFLP loci detected in the WV family were also polymorphic. This finding supports the possibility that these RFLP markers may serve as anchor loci in many other peach crosses.
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