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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.
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.
Abstract
The mean inbreeding and coancestry coefficients of Japanese-type plums grown in California and the southeastern United States were one-half or less of those calculated for peach. The three most important founding clones for the major California cultivars were ‘Santa Rosa’, ‘Eldorado’, and ‘Gaviota’; for the plums of the southeastern United States they were ‘Methley’, ‘Santa Rosa’, and ‘Mariposa’. The species background of both groups of plums was ≈50% P. salicina, although the sources of P. salicina differed between groups. For the California cultivars, the other half was composed of P. simonii and P. americana, whereas, for the southeastern group, the major contributing species was P. cerasifera, with lesser contributions from P. simonii, P. americana, P. angustifolia, and P. munsoniana.
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.
Despite the hundreds of existing stone fruit (Prunus spp.) cultivars used for fresh market, there is a continuing need to develop new stone fruit cultivars as the requirements of the industry change. Over the last 20 years there has been a shift toward private breeding as the public sector decreases its support of these long-range programs. As a result there are fewer public breeding programs and many of those still operating protect their releases and partially fund their programs with royalty payments. Other trends that are shaping the development of new stone fruit cultivars are a need for smaller or more easily managed tree architecture, a trend toward the use of fewer agricultural chemicals, the expansion of production zones into the milder winter zones to allow year-round availability of stone fruit, a general diversification of fruit types being marketed, the increased awareness of the health benefits of fruit consumption, the need for better and more consistent quality, and given the global marketing of these fruit the increased need for enhanced postharvest qualities. The breeding programs of the world are responding to these trends and working toward developing the cultivars for the world markets of the future.
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%.
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.
Abstract
A nondestructive method for evaluating the salt tolerance of Prunus seedlings was devised for greenhouse sand-culture with 60 days of saline drip irrigation. The treatments contained half-strength Hoagland's solution using distilled water and supplementary chloride and sulfate salts of Na, Ca, and Mg to reach 1.5 dS·m–1 for control, 4.5 dS·m–1 for the first trial, and 6.0 dS·m–1 for the second and third trial screenings. After 60 days of irrigation with 6.0 dS·m–1 Nemaguard, the standard peach [P. persica (L.) Batsch] rootstock averaged 46% of the fresh weight, 53% of the volume, 66% of the height, and 74% of the foliar health ratings of the control seedlings. Percent of control values were compared for a tentative ranking of salt tolerance: ‘Titan’ almond × Nemaguard and P. mexicana Wats. > Nemaguard and Nemared > Myrobalan plum (P. cerasifera J.F.Ehrh.) and bitter almond (P. amygdalus var. amara Focke.). Correlation coefficients were used in selecting useful sets of evaluation parameters. Height was rejected as a screening parameter. Final fresh weight and a final foliar health rating are recommended for cursory screenings of Prunus germplasm. The last three weekly foliar health scores are useful for comparing rates of decline. Volume displacements are useful for comparing root vs. shoot growth.