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Abstract
Significant differences in firmness were detected when the Instron Universal Testing Machine was used to test fruit firmness in a group of 13 sour cherry (Prunus cerasus L.) cultivars and selections. Deformation testing of intact fruit resulted in the establishment of seven statistically distinct firmness groups. Selections and cultivars that were firmer than ‘Montmorency’ were identified. Differences in skin strength, as determined by an Instron puncture test, were not as distinct. At harvest, firmness was not correlated with soluble solids content, fruit removal force or fruit weight, indicating the inadequacy of any of these parameters alone as an index of fruit maturity. Deformation testing with the Instron can be used to accurately assess whole fruit firmness in sour cherry breeding programs. Modification of the puncture test would be required to increase the precision in detecting differences in skin strength.
The ability to pre-screen apple populations for fruit color at an early seedling stage would be advantageous. In progeny of the cross `Rome Beauty' × `White Angel' red/yellow color variation was found to be highly correlated with the genotype at Idh-2, an isozyme locus that was heterozygous in both parents. We postulate that the red/yellow color variation was produced by a single gene linked to I&-2 and also heterozygous in both parents. This population was also screened with over 400 primers to detect randomly amplified polymorphic (RAPD) markers for fruit color. DNA extraction procedures were developed for bark, and DNA was extracted from bark samples and leaves. Red and yellow fruited individuals were examined in bulk. Several markers have been found that are linked to red color. A high density map is being constructed in this region. These markers are being examined in other crosses segregating for fruit color. The application of these markers will be discussed in relation to the inheritance and manipulation of fruit color.
Abstract
Flower bud survival following a freeze of –26°C was determined for ‘Redhaven’ peach [Prunus persica (L.) Batsch,] on its own roots and on eight other root-stocks. ‘Redhaven’ on GF655-2 and on ‘Amandier’ (GF677) had the lowest flower bud survival, with those on ‘Citation’ and ‘Damas’ (GF1869) having the highest percent survival. The effect of the rootstock on the number of flower buds per node and on the relative survival of these two bud types (single vs. paired) was not significant.
Abstract
Significant differences in total fruit firmness (skin and flesh) and flesh firmness were detected when the Instron Universal Testing Machine was used to perform puncture tests on whole fruit of 29 sweet cherry (Prunus avium L.) cultivars and selections. The ratio of flesh firmness to total firmness varied greatly among selections. Selections that were firmer than commercial cultivars were identified. Correlations between the firmness values and soluble solids content, fruit removal force, fruit weight, and the dimensions of the fruit were either small or not significant. The Instron was found to be an effective means of obtaining information on components of firmness in sweet cherry. The ability to assess both total firmness and flesh firmness is important for the selection and evaluation of firmness in breeding.
The S-alleles of 55 apple (Malus ×domestica Borkh.) cultivars and selections were determined using an allele-specific polymerase chain reaction (PCR) amplification system for 11 different S-alleles (S2, S3, S4, S5, S7, S9, S24, S26, S27, Sd, Sf). Four cultivars had S-alleles different than those predicted by their parentage. Three commercial cultivars of unknown pedigrees had S-genotypes that suggested `Delicious' and `Golden Delicious' were the parents. S-genotyping results supported controlled pollination test results. The genotypes of the five triploid cultivars examined were consistent with the unreduced gamete being contributed by the female parent. Although a large number of S-genotypes is available in apple, artificial selection or repeated use of the same cultivars as parents appears to have significantly restricted the number of compatibility groups associated with commercial clones. In controlled reciprocal crosses between two cultivars of known S-genotypes, the segregation of S-genotypes and S-alleles was 1:1:1:1, the ratio expected for random pairing of alleles.
Abstract
Fruit from 33 sweet cherry (Prunus avium L.) and 21 sour cherry (P. cerasus L.) genotypes were harvested at two stages of maturity (green and ripe). Unblemished fruit were inoculated with a suspension containing 103, 104, or 105 conidia of Monilinia fructicola (Wint.) Honey per ml, misted for 24 hours at 20C, then incubated 6 days at 20C and 95% to 97% RH. Percent fruit infection was determined and analyzed separately for sweet and sour genotypes. The effects of genotype, inoculum concentration, and stage of maturity, and all interactions between these factors, were significant. Sweet cherries were significantly more susceptible to infection than sour cherries at the green fruit stage, but not at harvest maturity.
Abstract
Foliar nutrient concentrations of ‘Redhaven’ peach [Prunus persica (L.) Batsch.] on its own roots and budded on eight rootstocks [vegetatively propagated GF 655-2, ‘Damas’ (GF 1869), ‘Amandier’ (GF 677), and ‘Citation’, and seedlings of ‘Hal-ford’, ‘Lovell’, ‘Bailey’, and ‘Siberian C’] were analyzed for two seasons. Rootstocks selected for calcareous soils (‘Amandier’, ‘Damas’, and GF 655-2) were the most efficient in accumulation of nutrients other than Mg and B, for which they were the least efficient. For N and P, the levels of foliar nutrients were within proposed sufficiency ranges, regardless of the rootstock. Foliar levels of K and Zn were below the sufficiency range for all rootstocks tested. Differences among rootstocks were most evident in the foliar levels of Ca, Mg, Fe, Mn, B, and Cu. Rootstock had a small but significant effect on the foliar nutrient concentration.
Molecular markers (isozyme and DNA) have been used to map apple and have helped to elucidate the inheritance of some morphological traits. In this project random amplified polymorphic DNA (RAPD) and isozyme markers were used to create maps for `Wijcik McIntosh, a columnar (reduced branching) sport of `McIntosh' and NY 75441-67, an advanced selection from the multiple disease resistance breeding program. NY 75441-67 is resistant to scab source of resistance from M. floribunda) and resistant to cedar apple rust. `Wijcik McIntosh' is being used in the breeding program as a source of the dominant gene, Co, for reduced branching, but there is also interest in this genotype because of the tremendous variation in plant form observed in progenies segregating for columnar habit. Some of these form variants may be of greater commercial interest than the parental material. Morphological traits examined in this progeny included plant height, stem diameter, suckering, branching habit, spur production, and internode length. The usefulness of molecular markers to pre-select for components of plant form is being examined. Molecular markers promise to aid our understanding and manipulation of quantitative morphological traits.
We mapped DNA polymorphisms generated by 41 sets of Simple Sequence Repeat (SSR) primers, developed independently in four laboratories. All primer sets gave polymorphisms that could be located on our `White Angel' x `Rome Beauty' map for apple [Malus sylvestris (L.) Mill. Var. domestica (Borkh.) Mansf.]. The SSR primers were used to identify homologous linkage groups in `Wijcik McIntosh', NY 75441-58, `Golden Delicious', and `Liberty' cultivars for which relatively complete linkage maps have been constructed from isozyme and Random Amplified Polymorphic DNA (RAPD) markers. In several instances, two or more SSRs were syntenic, and except for an apparent translocation involving linkage group (LG) 6, these linkages were conserved throughout the six maps. Twenty-four SSR primers were consistently polymorphic, and these are recommended as standard anchor markers for apple maps. Experiments on a pear (Pyrus communis L.) population indicated that many of the apple SSRs would be useful for mapping in pear. However some of the primers produced fragments in pear significantly different in size than those in apple.