A standardized screening procedure for tolerance to bicarbonate-induced Fe chlorosis using a commercial fertilizer mix (Plantex) as the nutrient source, high solution pH (8.5) and 1.5 m m bicarbonate to simulate a calcareous soil situation was used with a 1 vermiculite:1 perlite (v/v) support media, small pots and topping (pinching back the tops of shoots). The tolerance level of peach [Prunus persica (L.) Batsch] rootstock could be assessed by leaf visual-chlorosis ratings and Spad-502 chlorophyll readings instead of extractable leaf-chlorophyll concentration or plant Fe concentration. Although most of the tolerant genotypes had almond [P. amygdalus (Mill.) D.A. Webb] in their parentage, a few peaches (`Swat', NJ672281007) showed high to moderate levels of tolerance.
Fourteen Prunus rootstocks were evaluated against mixtures of several isolates of the root-lesion nematode Pratylenchus vulnus Allen and Jensen in three greenhouse experiments. Most of the tested rootstocks are new releases or materials in advanced stages of selection that also have incorporated root-knot nematode resistance. The plums Torinel (Prunusdomestica L.) and Redglow (P. salicina Lindl. P. munsoniana Wight and Hedrick cv. Jewel) showed a moderately resistant response; their final nematode population levels were lower or slightly higher than inoculation levels. Low nematode reproduction also was found in the peach–almond hybrid G N No 22 [P. persica (L.) Batsch P. dulcis (Mill.) D.A. Webb] and the plum Bruce (P. salicina P. angustifolia Marsh.), and although these rootstocks did not perform as well as Torinel and Redglow, they also appear to be poor hosts for P. vulnus.
Callus formation and adventitious shoot regeneration in vitro from mature stored seed were evaluated in eight ornamental cherry (Prunus) taxa: P. campanulata Maxim., P. maackii Rupr., P. sargentii Rehd., P. serrula Franch., P. serrulata Lindl., P. subhirtella Miq., P. virginiana L., and P. yedoensis Matsum. Several portions of the embryo (cotyledons and hypocotyl sections) and nine combinations of growth regulators (BA, 2,4-D, IBA, NAA, and TDZ) were compared. Effects of embryo portions and growth regulator treatments were generally small within taxa, but shoot formation differed among taxa. About 20% to 50% of the embryos from P. virginiana and P. serrula and ≈5% to 30% of those from P. maackii produced shoots. The other taxa generally did not produce shoots. Regeneration from mature stored seed in the responsive taxa represents a potential system for genetic transformation. Chemical names used: 6-benzyladenine (BA); 2,4-dichlorophenoxyacetic acid (2,4-D); indole-3-butyric acid (IBA); α-naphthaleneacetic acid (NAA); thidiazuron (TDZ).
On the basis of investigating pollination habits of 45 cultivars of Mei Hua, interspecific hybridization between Mei Hua and apricot (Prunus armeniaca). David's peach (P. davidiana) as well as siberian apricot (P. sibirica) were made from 1982 to 1991. With total number of pollination flower 17,050, 168 hybrid seed and 75 hybrid seedlings were obtained. Embryo culture in vitro was used for undeveloped young hybrid embryos. Test of freezing resistance both in artificial freezing and in overwintering for the hybrid seedlings showed that there were 5 hybrids with double and nice flower to be very hardy to low temperature. They were able to tolerate as low as -35C for 30 days in open ground, and now they were planted in northwest China's Gansu province and northeast China's Liaonin province without cold injury.
Mei (Prunus mume Sieb. et Zucc.) flower is one of the candidates for the national flower of the People's Republic of China. Several major anthocyanins from the flowers of P. mume Sieb. et Zucc. were isolated with MeOH-HOAc-water (10:1:9, v/v), and purified by paper chromatography and subsequent column chromatography. Specific chemical reactions, chromatographic and spectroscopic analyses indicated that the anthocyanins in `Nanjing Hongxu' (Nanjing red-bearded) were cyanidin 3-O-(6'-O-α-rhamnopyranosyl-β-glucopyranoside) and cyanidin 3-O-(6'-O-galloyl-3'-O-β-glucopyranosyl-β-glucopyranoside). Anthocyanins in `Nanjing Hong' (Nanjing red) were cyanidin 3-O-(6'-O-α-rhamnopyranosyl-β-glucopyranoside), cyanidin 3-O-(6'-O-galloyl-β-glucopyranoside) and cyanidin 3-O-(6'-O-E-feruloyl-βglucopyranoside). In addition to contributing to the blue flower color, the anthocyanins may improve the ability of the two cultivars to survive at low temperatures.
55 ORAL SESSION (Abstr. 473-479) Tree Fruit: Prunus Culture and Management
Leaf segments of Prunus persica L. (peach) collected from greenhouse-grown plants and from micropropagated shoots were cultured on a basal medium containing half-strength Murashige and Skoog (MS), Staba vitamins, sucrose (30 g/1) and agar (6.5 g/l); medium adjusted to pH 5.6. The influence of 6 different growth regulators at 3 concentrations (5, 10, 15 μM) were investigated using leaf explants from proliferating shoots of 'Elberta Queen' peach. With thidiazuron (TDZ), compact and multiple green calli were obtained; with benzyladenine and zeatin, lower numbers of small sized calli were obtained; with kinetin, no callus development was observed. Among auxin treatments, both Dicamba and 2,4-D resulted in friable white and yellow calli. Most of the calli produced in all treatments were formed along the cut margins of the explants. In an another experiment, leaf explants of' Bellaire' (greenhouse) and `Elberta Queen' (in vitro shoots) were used to determine the influence of a large scale concentration of TDZ (3 to 23 |iM). Explants from greenhouse and in vitro leaves resulted in higher levels of callus development at TDZ concentrations of 8-13 μM. Higher TDZ levels resulted in necrosis of leaf explants. The-influence of different carbon sources on callogenesis was investigated. We observed more green and compact calli with glucose than with sucrose and fructose at 100 mM. The influence of the glucose at 10 different concentrations (30 to 300 mM) was also investigated.
Twenty-eight Prunus species were examined in order to survey their genetic diversity. Genomic DNA was extracted from 36 varieties and used for the template DNA of PCR. DNA fingerprints were generated by random primers or semi-random primers, some primers consensus to the repeated units as telomers, and three sets of sequence-tagged primers specific to domains of chloroplast DNA (psbA, rbcL-ORF106, atpB-rbcL). PCR products generated from these three domains were digested by 12 restriction enzymes. RFLPs were detected among varieties and subjected to the UPGMA. Thirty-six varieties were classified approximately into two groups: “Plum group” and “Cherry group.” It was inferred that these two groups were divided in old time. P. tomentosa, P. japonica, P. glandurosa, and P. besseyi, which are classified into the cherries, showed the same fingerprint patterns from chloroplast DNA of the plum group; plums and cherries have a large genetic diversity. It was supposed that the diversity of plums depended on nuclear DNA, besides the diversity of cherries on both nuclear and chloroplast DNA.
Flower buds of Prunus serotina Ehrh. produced high temperature exotherms (HTEs) and low temperature exotherms (LTEs). Supercooling in P. serotina occurred during full dormancy in December and early January but disappeared thereafter, whereas no supercooling was observed in P. padus L. or P. virginiana L. Both intact and detached lnflorescences of P. serotina supercooled and froze as a unit and not as individual florets. Exotherms in dehydrated parts occurred at lower temperatures than in hydrated parts. Dormant buds of P. serotina lost the detectable exotherms when kept at -7C for 2 days, while buds stored at 3C exhibited LTEs between -20 and -26C. Dormant Morescences of P. serotina were filled with elongated procambium and pith cells. In contrast, P. padus and P. virginiana had differentiated xylem vessel elements (XVE) the entire length of the inflorescence and did not supercool. Bud scales and bud axis of P. serotina were the flower parts where water apparently migrated during storage at 3 and -7C. This was not observed for P. padus and P. virginiana flower buds. The rate of water migration from the inflorescences to bud scales and axis probably plays a role in the freezing behavior of P. serotina.
An Agrobacterium-mediated transformation system was developed for chokecherry (Prunus virginiana L.), one of the most popular native small tree or large shrub species for resource conservation and wildlife habitat in North America. Leaf tissues from in vitro plants previously maintained in MS medium with 2.5 μm BA were co-cultivated on woody plant medium (WPM) containing 10 μm BA and 200 μm acetosyringone with Agrobacterium tumefaciens strain EHA105 harboring the binary Ti plasmid pBI121 carrying the uid A gene encoding for β-glucuronidase (GUS) and the npt II gene encoding neomycin phosphotransferase II. Infected leaf explants were disinfected in sterile water and antibiotics and then transferred to WPM containing 10 μM BA and the antibiotics cefotaxime, carbenicillin, and kanamycin (CCK) for shoot regeneration at 25 °C with a 16-hour photoperiod. Agrobacterium concentration, pre-conditioning of explants, application of acetosyringone, infection time, and kanamycin tolerance of leaf tissues were evaluated for effects on transformation efficiency. Regeneration of chokecherry shoots on kanamycin-containing medium and screening by GUS histochemical assays showed that both the npt II and the uid A genes were successfully transferred into chokecherry. The transformation will be further confirmed by polymerase chain reaction (PCR) and Southern blot analyses.