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  • Author or Editor: Susan K. Brown x
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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.

Open Access

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.

Open Access

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.

Open Access

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.

Open Access

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.

Free access

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.

Open Access

Despite the demonstrated importance of gibberellins (GAs) as regulators of fruit tree stature, information on their in vivo metabolism in apple vegetative tissues is still lacking. To determine whether the GA content and metabolism differs between dwarf and standard phenotypes and the influence of rootstocks, [14C]GA12, a common precursor of all GAs in higher plants, was applied to vigorously growing apple (Malus ×domestica) shoots collected from the scion cultivar Redcort on MM.106, a growth-promoting rootstock, and dwarf and standard seedlings on their own roots from progeny 806 (a cross between a breeding selection with reduced stature and an advanced breeding selection with a standard tree form). Twenty-one metabolites were identified by high-performance liquid chromatography (HPLC) and used as tracers for the purification of endogenous GAs. The existence of endogenous and [2H]-labeled GA12, GA15, GA53, GA44, GA19, GA20, and GA3 was demonstrated by gas chromatography–mass spectrometry (GC-MS); GA20 was the major GA present, with slightly less GA19 and GA44, and with GA3 present at approximately one-third the level of GA20. Despite specific searching, neither GA4, GA7, GA1, nor GA29 was found, showing that [14C]GA12 is metabolized mainly through the 13-hydroxylation pathway and that GA3 is a bioactive GA in apple vegetative tissues. The invigorating rootstock led to a slow GA metabolic rate in ‘Redcort’. For self-rooted plants, the same GAs were identified in dwarf and standard seedlings from progeny 806, although standard plants metabolized at twice the speed of dwarf plants. Young branches of dwarf 806 plants treated with GA3 were one-third longer with more nodes but similar in internode length. We conclude that the dwarf phenotype in progeny 806 is not caused by a lack of certain GAs in the GA biosynthesis pathway downstream of GA12.

Free access

Genetic linkage maps were created for three apple (Malus ×domestica Borkh.) cultivars using data from two progenies (`Wijcik McIntosh' xNY 75441-67 and `Wijcik McIntosh' xNY 75441-58). The maps consist primarily of randomly amplified polymorphic DNA (RAPD) markers, but also contain six isozyme loci and four morphological markers (Rf , fruit skin color; Vf , scab resistance; Co, columnar growth habit; Ma, malic acid). Maps were constructed using a double pseudotestcross mapping format and JoinMap mapping software. An integrated `Wijcik McIntosh' map was produced by combining marker data from both progenies into a single linkage map. Homologous linkage groups from paternal maps were paired with their counterparts in the `Wijcik McIntosh' map using locus bridges composed of markers heterozygous in both parents of a progeny. The `Wijcik McIntosh' map consists of 238 markers arranged in 19 linkage groups spanning 1206 cM. The NY 75441-67 map contains 110 markers in 16 linkage groups and the NY 75441-58 map consists of 183 markers in 18 linkage groups. The average distance between markers in the maps was ≈5.0 cM.

Free access

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.

Free access