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- Author or Editor: David Byrnes x
- HortScience x
Fruit and ornamental breeders were surveyed about their use of molecular markers in either their breeding programs or in their related research programs. Responses were obtained from over 100 fruit and ornamental breeding programs from throughout the world. Of these, less than 50% used molecular markers in their programs. The two most common uses of these markers were for studies in plant identification and diversity. These were followed by the use of markers in developing molecular maps, in discovering molecular tags and/or trying to identify the genes for specific plant traits, for marker assisted selection, and finally, for the elucidation of plant taxonomy. In conclusion, although there is much research in this area, few programs are actually using markers in the context of an applied breeding program. The major reason for this situation is the lack of available markers and the cost of using these markers to screen large numbers of progeny. Those that use markers in their breeding tend to use them to verify the genotype of the parents or confirm the genotype of selected seedlings rather than screen unselected seedlings.
The diploid cultivated plum, or the Japanese plum is a group of plants in which several plum species have been incorporated. Within the cultivated plum two germplasm pools are recognizable: the California and the Southeastern groups. A comparison of the isozyme variability at 11 loci between the two groups shows that the California germplasm is two to three fold less variable in terms of both percent of polymorphic loci and mean heterozygosity than the Southeastern germplasm. The greater isozyme variability within the Southeastern germplasm is due to the alleles derived from P. angustifolia and P. cerasifera which have been used as sources of disease resistance in the development of plums adapted to the humid plum growing areas of the southeastern United states.
Poor germination in Rosa has been an obstacle to breeding programs for years. Rose breeders generally stratify rose seed under cool, moist conditions for 4-10 weeks by planting directly into the seedling flat/bed or in a small container followed by planting the germinating seed into the seedling flat/bed. This experiment used 9 genotypes and compared these two approaches combined with variations in the stratification media (sand, perlite, sphagnum moss and Sunshine Mix #4). Over all stratification media and genotypes, germination was not influenced by whether the seed was stratified directly in the seedling flat/bed or in a small container. However, the process of transplantation of the delicate germinating seed from the small container to the flat/bed resulted in greater mortality of the germinating seedlings. he stratification media affected the germination of the rose seed. Sunshine Mix #4 gave the best germination as compared to all other media types tested. As expected the germination of the genotypes varied greatly, ranging from 0.7% to 37.1%.
Abstract
Genetic analysis of five presumptive isozyme loci in apricot (Prunus armeniaca L. and related species) revealed that the variation observed was controlled by two or three alleles in a simple Mendelian manner. This increases the number of known simply inherited traits in apricot from one to six. Linkage was not detected between MDH-1 and MDH-2.
Abstract
I would like to clarify the difference between two words that are frequently misused in our publications. I suppose the words “pollenizer” and “pollinator” have been confused since their invention, given their consistent misuse in at least one major pomology text (Tree Fruit Production by Tesky and Shoemaker). A pollinator is the agent of pollen transfer, which, in many species, are bees or some other insects; a pollenizer is the source of pollen, which is usually a flowerproducing plant. One recent paper talks of “planting of pollinators”, which brings up visions of planting bees in the orchard, and of “pollinator frequencies”, which indicates the author is referring to bee hive density, when the author was really referring to the density of trees as pollen sources. Another author was describing parentage of some tree fruits and said that cultivar A “was the progeny of unrelated unknown pollinators of” cultivar B. How fruit trees can be the progeny of fruit insects is beyond me! Of course, the authors meant to use the word “pollenizer”, not “pollinator”. Similar mistakes have been made throughout the literature equally by professionals in a range of disciplines.
Seedlings from three interspecific backcross rose populations derived from a F1 population were used to study inheritance of several traits in roses. Three F1 plants (WOB13, WOB21, and WOB26) from the hybridization of the diploid parents Rosa wichuraiana and `Old Blush' were backcrossed to `Old Blush' to produced three populations to observe the segregation of several morphological and disease resistance traits. The segregating rose traits in the backcrosses are no prickles on stems, non-recurrent blooming habit, white single flowers, black spot resistance, and powdery mildew resistance present in the Rosa wichuraiana parent compared to prickles on stems, recurrent blooming habit, pink double flowers, black spot susceptible, and powdery mildew susceptible present in the `Old Blush' parent. Visual data was collected for the segregating traits using color standards and rating scales as appropriate. The three populations expressed the segregating traits to varying degrees. Under the environmental conditions at College Station, Texas the population `Old Blush' × WOB26 had a greater expression of the traits for no prickles on stems, recurrent blooming habit, disease resistance to black spot, and disease resistance to powdery mildew, which are traits desired in breeding programs. The segregation of flower color (white/pink), and flower type (single, semi double, and double) were similar in all three populations.
The hybrid origin of 23 rose (Rosa spp.) accessions was examined with three isozymes: acid phosphatase (E.C.3.1.3.2), malate dehydrogenase (E.C.1.1.1.37), and phosphoglucose isomerase (E.C.5.3.1.9). All three isozymes were useful for interspecific hybrid verification. This procedure was effective if the putative parents were known and differed in isozyme phenotype. To verify the origin of hybrid species or cultivars with hybrid origins, isozymes were useful but limited by the number of generations since the original hybridization and the number of accessions of the putative parental species assayed.