Author :- JaymalaRose, the queen of flowers, the most universally recognized and beloved flower in the concern representing love, affection, compassion, purity, innocence and passion, belongs to the family Rosaceae. The genus Rosa include more then 1400 cultivars and 150 specie.
The genus Rosa is further classify into 4 sub genera, Eu Rosa, Platyrhodon, Hesperhodes, and Hulthemia, and diffuse widely throughout the northen hemisphere. The subgenus Eu Rosa includes 11 sections.
The sections Caninae and Cinnamomeae are the largest and comprise about 50 and 80 species, respectively (Wissemann, 2003) Indo-Pak subcontinent has always been the sight of attraction for the whole concern regarding its natural flora. About 25 species hit been reportable growing in this Atlantic and some of them hit contributed to the development of modern ornamental roses.
The genus Rosa is commonly subdivided into four subgenera, the largest of these is subgenus Rosa with 10 sections. Most of the genetically analysed rose species appear to be sexual and diploid (2n = 14) or tetraploid (2n = 28) although there are a some triploid (2n = 21), hexaploid (2n = 42) and octaploid species (2n = 56).
The diploid species are commonly self-incompatible whereas the polyploids are self-fertile. Pollen stainability is commonly high in all species with even ploidy levels, i.e. 2x, 4x or 6x. Rose species are commonly sexual and hit a regular meiosis but there is one deviating section, Caninae, which harbours the so-called dogroses.
Most of these are 5x but there are some taxa with 4x and 6x. Only heptad chromosomes (derived from heptad bivalents) are transmitted through the pollen grains, whereas egg cells include 21, 28 or 35 chromosomes (derived from heptad bivalents and 14, 21 or 28 univalents) depending on the ploidy level.
Apomixis occurs occasionally in the dogroses and genetic selfing is probably common since these taxa are self-fertile. Interspecific hybridization takes place spontaneously among rose species at all ploidy levels and is used as a potent tool in plant breeding.
Information about compatibility, nurture system, pollen viability, chromosome number and inheritance is essential for optimal utilization of crosses in rose breeding.
The organisms with more than digit genomes
are called polyploids. Among plants and animals, the polyploidy occurs in a binary series of 3, 4, 5, 6, 7, 8, etc., of the basic chromosome or genome number and thus is causing triploidy, tetraploidy, pentaploidy, hexaploidy, heptaploidy, octaploidy, respectively.
Ploidy levels higher than tetraploid are not commonly encountered in natural populations, but our most essential crops and ornamental flowers are polyploid, e.g., wheat (hexaploid, 6n), strawberries (octaploid, 8n), some commercial fruit and ornamental plants, liver cells of man, etc. Other examples of polyploidy among plants and animals are following.
A continuous polyploid series has been reportable in rose plant. A euploid series of basic number of 7 (monoploid) including diploids (2n= 14), triploids (21), tetraploids (28), pentaploids (35), hexapolid (42), and octaploid (56) has been reportable in different species of Rosa. Likewise, the genus Chrysanthemum has basic chromosome number 9 and has a euploidic series of diploid (2n = 18), tetraploids (4n=36), hexaploids (6n=54), octaploids (8n=72) and decaploids (10n=90) in its different species.
GENE MAPPING IN ROSE:
Parental linkage maps of a segregating accumulation of diploid rose hybrids (2n=2x =14), composed of 365 uni-parental AFLP and SSR markers, hit been constructed using a accumulation (n=88) derived from a cross between digit half-sib parents (P119 and P117).
the markers, 157 P119 markers (85 %) mapped on eight linkage groups and 133 P117 markers (78 %) on heptad linkage groups. The resulting linkage maps of P119 and P117 spanned 463 cM and 491 cM with an cipher of interval between markers of 2.9 cM and 3.7 cM, respectively.
The present genetic maps were used to identify decimal trait loci (QTLs) for digit ontogeny vigour-related traits, foliage Atlantic and chlorophyl content, using the Multiple QTL Mapping approach. Three QTLs for foliage Atlantic and digit QTLs for chlorophyl content were identified.
The QTLs accounted, in total, for 50.8 % (range 7.0-23.1 %) and 25.8 % (range 7.6-18.2 %) of the amount phenotypic variance for foliage Atlantic and chlorophyl content, respectively. The detection of highly significant major QTLs enables
Plant nurture using symbol aided selection is a second way to use a gene map. If you know where a gene is on a gene map, DNA markers that flank the gene of welfare crapper be identified.
Just like distance markers on an interstate route indicate where you are on the highway, the proximity of the DNA markers would infer the proximity of the delectable gene in the offspring.
DNA markers crapper be detected soon after seed germination, as soon as a some leaves are available to use for DNA symbol analysis. This process makes early detection of the proximity of the gene possible even though the actual expression of the trait does not occur until much later in maturation.
This is especially valuable, for example, when employed with genes that control anthesis in plants that take some years to bloom and fruit or traits much as disease status that take several years to evaluate.
Therefore, DNA markers tightly linked to a gene crapper be used by breeders to select and cull nurture lines. Also if several genes exist for status to a disease, e.g., black spot, DNA markers crapper be used to \"stack\" these genes into one rose.
Additionally, once a gene is identified, its function and the biochemical steps leading to the trait being spoken crapper be studied and its genetic control understood.
