Anita N. Azarenko

NITROGEN PARTITIONING IN APPLE AS AFFECTED BY TIMING AND TREE GROWTH HABIT

SummaryNine year old standard-(Std) ‘Topred Delicious’ and spur-type ‘Redspur Delicious’ apple trees (Malus domestica Borkh.) on Mailing 7A (M.7A) rootstocks were fertilized with ground-applied ammonium nitrate or foliarly-applied urea depleted in 15N on various dates. The treatments consisted of a ground application in spring (March) (SG), a pre-harvest ground application in August (PHG), a foliar spray in fall (September) (FF), or a combination of each of the last two treatments with SG (SG/PHG and SG/FF). All trees received a total of 120 g N each with the exception of FF trees, which received half the dose. Labelled N from the SG application was allocated preferentially to the fruit, leaves, shoots, and branches and to a lesser extent to the roots. Leaves on young shoots had higher concentrations of 15N label than those on older shoots or spurs, indicating an increasing dependence of the tree on soil N from spring to summer. The amount of N allocated to above-ground tissues decreased as the season pro...

Identification of random amplified polymorphic DNA (RAPD) markers for self-incompatibility alleles in Corylus avellana L.

Abstract Random amplified polymorphic DNA (RAPD) markers were identified for self-incompatibility (SI) alleles that will allow marker-assisted selection of desired S-alleles in hazelnut (Corylus avellana L.). DNA was extracted from young leaves collected from field-planted parents and 26 progeny of the cross OSU 23.017 (S1S12)×VR6-28 (S2S26) (OSU23×VR6). Screening of 10-base oligonucleotide RAPD primers was performed using bulked segregant analysis. DNA samples from 6 trees each were pooled into four ‘bulks’, one for each of the following: S1 S2, S1 S26, S2 S12, and S12 S26. ‘Super bulks’ of 12 trees each for S1, S2, S12, and S26 were then created for each allele by combining the appropriate bulks. The DNA from these four super bulks and from the parents was used as a template in the PCR assays. A total of 250 primers were screened, and one RAPD marker each was identified for alleles S2 (OPI07750) and S1 (OPJ141700). OPJ141700 was identified in 13 of 14 S1 individuals of the cross OSU23×VR6 used in bulking and yielded a false positive in 1 non-S1 individual. This same marker was not effective outside the original cross, identifying 4 of 5 S1 progeny in another cross, ‘Willamette’×VR6-28 (‘Will’×VR6), but yielded false positives in 4 of 9 non-S1 individuals from the cross ‘Casina’×VR6-28 (‘Cas’×VR6). OPI07750 served as an excellent marker for the S2 allele and was linked closely to this allele, identifying 12 of 13 S2 individuals in the OSU23×VR6 population with no false positives. OPI07750 was found in 4 of 4 S2 individuals from ‘Will’×VR and 7 of 7 S2 individuals of ‘Cas’×VR6 with no false positives, as well as 10 of 10 S2 individuals of the cross OSU 296.082 (S1S8)×VR8-32 (S2S26), with only 1 false positive individual out of 21 progeny. OPI07750 was also present in 5 of 5 cultivars carrying the S2 allele, with no false-positive bands in non-S2 cultivars, and correctly identified all but 2 S2 individuals in 57 additional selections in the breeding program. In the OSU23×VR6 population, the recombination rate between the marker OPJ141700 and the S1 allele was 7.6% and between the OPI07750 marker and the S2 allele was 3.8%. RAPD marker bands were excised from gels, cloned, and sequenced to enable the production of longer primers (18 or 24 bp) that were used to obtain sequence characterized amplified regions (SCARs). Both the S1 and S2 markers were successfully cloned and 18 bp primers yielded the sole OPJ141700 product, while 24-bp primers yielded OPI07750 as well as an additional smaller product (700 bp) that was not polymorphic but was present in all of the S-genotypes examined.

Does the genome of Corylus avellana L. contain sequences homologous to the self-incompatibility gene of Brassica?

Self-incompatibility is a genetic mechanism enforcing cross-pollination in plants. Hazelnut (Corylus avellana L.) expresses the sporophytic type of self-incompatibility, for which the molecular genetic basis is characterized only in Brassica. The hypothesis that the hazelnut genome contains homologs of Brassica self-incompatibility genes was tested. The S-locus glycoprotein gene (SLG) and the kinase-encoding domain of the S-receptor kinase (SRK) gene of B. oleracea L. were used to probe blots of genomic DNA from six genotypes of hazelnut. Weak hybridization with the SLG probe was detected for all hazelnut genotypes tested; however, no hybridization was detected with PCR-generated probes corresponding to two conserved regions of the SLG gene. One of these PCR probes included the region of SLG encoding the 11 invariant cysteine residues that are an important structural feature of all S-family genes. The present evidence suggests that hazelnut DNA hybridizing to SLG differs significantly from the Brassica gene, and that the S-genes cloned from Brassica will not be useful for exploring self-incompatibility in hazelnut.

Postharvest nitrogen application effect on ovule longevity of ‘cornice’ pear trees

Abstract Low fruit set and cropping are common characteristics of ‘Cornice’ pear (Pyrus communis L.) trees in spite of a high bloom density. An experiment was conducted to study the effect of late season nitrogen (N) application on ovule longevity of this cultivar. Mature trees were given a single foliar application of 0% (control), 5%, or 10% (w/v) aqueous urea immediately after harvest. Ovule senescence was detected by fluorescence microscopy. Ovule longevity was extended and fruit set was increased by fall urea. Flower density and fruit fresh weight were not affected.

Endogenous IAA levels and development of coffee flower buds from dormancy to anthesis

Dormant coffee (Coffea arabica L.) flower buds require water stress to stimulate regrowth. A xylem specific water-soluble dye, azosulfamide, was used to quantify water uptake of buds after their release from dormancy by water stress. In non-stressed flower buds, the rate of water uptake was generally slower and variable compared to stressed flower buds, where the rate of uptake tripled from 1 to 3 days after rewatering and preceded the doubling of fresh and dry weight of buds. Free, ester and amide IAA levels of developing flower buds were measured by gas chromatography-mass spectrometry-selective ion monitoring using an isotope dilution technique with [13C6]IAA as an internal standard. Throughout development, the majority of IAA was present as amide IAA. The proportions of amide and free IAA increased one day after plants were released from water stress, and preceded the doubling of fresh and dry weight. Free and conjugated IAA content per bud remained stable during the period of rapid flower growth until one day before anthesis.