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Zhaohui Li, Yan Ma, Wanyuan Yin, Dekui Zang, and Xianfeng Guo

reports of cutting propagation of P. tatarinowii have been published. The present study was performed to explore stem cutting techniques for P. tatarinowii . The specific objectives were, first, to screen the appropriate exogenous auxin treatment and

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Sunghee Guak, Michael Beulah, Norman E. Looney, and Leslie H. Fuchigami

Three experiments were conducted at two locations, two at Summerland, British Columbia, Canada and one at Corvallis, Ore., to evaluate synthetic auxins (MCPB-ethyl or NAA) and ethephon as blossom thinners for `Fuji' apple [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.]. These experiments also involved application of carbaryl at 1000 mg·L-1 in the postbloom period. All blossom thinners were sprayed at 85% full bloom while carbaryl was applied at 11-mm fruit diameter. Within these experiments, MCPB-ethyl at up to 20 mg·L-1 or NAA at up to 21 mg·L-1 increased whole flower cluster removal linearly with rate; however, with the Corvallis experiment MCPB-ethyl failed to result in any thinning. Neither auxin treatment consistently reduced fruit set on the remaining clusters, resulting in “clustering”. Bloom-time application of ethephon at 100 mg·L-1 with NAA further reduced crop load. Carbaryl reduced total crop load by increasing both whole cluster removal and number of sites with a single fruit. Return flowering was not improved by the auxin treatments except where there was very excessive crop reduction. Ethephon or carbaryl promoted return flowering with the carbaryl effect being more pronounced. However, this carbaryl effect was significantly countered by the bloom-time auxin whereas ethephon overcame the negative effects of the auxin treatments. The combined use of ethephon and carbaryl was effective in terms of both crop reduction and return flowering benefits. Chemical names used: 1-naphthyl N-methylcarbamate (carbaryl); 2-chloroethylphosphonic acid (ethephon); ethyl 4-(4-chloro-2-methylphenoxy) butanoate (MCPB-ethyl); and 2-(1-naphthyl) acetic acid (NAA).

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Jules Janick, Anna Whipkey, S.L. Kitto, and J. Frett

Shoot proliferation of Japanese plum yew [Cephalotoxus harringtonia (Forbes) K. Koch] derived either from a seedling or from a mature clone was achieved in a medium based on Murashige and Skoog salts supplemented with vitamins and casein hydrolysate in the presence of 10% (v/v) coconut water. Rooting was unsuccessful from microcuttings proliferated on agar-based medium, but, when cultured in liquid medium on membrane rafts, detached shoots rooted under mist in greenhouse conditions with or without auxin treatments. Rooted microcuttings successfully acclimated to greenhouse conditions.

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Mateja Štefančič, Franci Štampar, and Gregor Osterc

The influence of two exogenously applied auxins (IAA and IBA) on the root and shoot development of leafy cuttings was analyzed at 'GiSelA 5', the dwarfing cherry rootstock. IBA (indole-3-butyric acid) hindered the callus formation in the early period of root development and it was more successful than IAA (indole-3-acetic acid) in promoting earlier root development. IBA also influenced the stronger shoot growth and the development of acrobasal type of the rooting system, and induced higher number of roots. Those parameters are very important for the quality and survival of the new plants and they are not the consequence of the higher IAA content in the rooting zones of cuttings in the first days of root development. Both auxin treatments had no effect on the final percent of the rooted cuttings neither on the survival of cuttings, but they increased the percent of rooted cuttings without callus. The root system with callus proved less qualitative, because the cuttings with such root system developed significantly less roots per rooted cutting and their shoot length was shorter than those of the cuttings without callus at both auxin treatments. Exogenously applied auxins were not crucial for root formation, however their application resulted in higher percent of more qualitative 'GiSelA 5' leafy cuttings. IBA proved as the most efficient treatment and it additionally induced earlier root formation.

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Clare Bowen-O'Connor, John Hubstenberger, Dawn Van Leeuwen, and Rolston St. Hilaire

Double-node microshoots of bigtooth maple (Acer grandidentatum Nutt.) were rooted in vitro on Driver-Kuniyuki Walnut (DKW) tissue culture media containing indole acetic acid (IAA). Microshoots represented six sources from three locations within Texas and New Mexico. Microshoots were placed in Phytatrays II™ containing DKW media with no plant growth regulator (DKW0) to reduce the high cytokinin levels used for shoot proliferation. Microshoots were induced to form roots for 15 days by placing them on DKW media containing IAA at 0.01, 1, 2.5, 5, 10, 15 or 20 μmol. Rooting frequency, the number of leaves and callus area were recorded every 30 days for 60 days. Rooting frequency increased up to 29% as IAA concentration increased (P= 0.004). However, as much as 71% of shoots for one of the three Guadalupe Mountain, Texas, sources rooted without auxin treatment after 30 days. The IAA concentration also affected the number of leaves per shoot (P= 0.0228) which averaged seven and callus area (P= <0.0001) which averaged 52 mm2. Average leaf size was 307 mm2. We conclude that IAA induces rooting in microshoots of bigtooth maple after 15 days of root induction. However, one source rooted without auxin treatment. The presence of callus does not interfere with root formation.

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William M. Proebsting

Douglas-fir clones have a wide range of rooting potential, but the species is generally considered difficult to root. We have reported previously that NAA is approximately 14-times more active than IBA in the clones tested, with an optimum of about 5 to 10 mM NAA. In contrast, other programs routinely use about 25 mM IBA to propagate Douglas-fir cuttings, a concentration that is relatively inactive in our clones. To address questions raised by these observations, we have incorporated auxin treatments into our long term program to select Douglas-fir clones with high rooting potential. We collect 20 cuttings of each clone identified in Christmas tree plantations, and retain clones rooting ≥ 80%. Beginning in 1991, we treated 10 cuttings of each clone with 5 mM NAA, the other 10 cuttings with 25 mM IBA. Over three years, 1158 clones received the split treatments. Of 222 clones rooting ≥ 80%) approximately half rooted ≥ 80% in response to NAA only. The remainder either responded to IBA or to both NAA and IBA. These results support our previous observations that NAA stimulates rooting of Douglas-fir better than IBA. However, they also suggest that there may be clones sensitive to IBA or to both NAA and IBA.

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Barbara M. Reed

Cultures of 49 Pyrus species and cultivars and one Pyronia (Pyrus × Cydonia hybrid) selection were screened in vitro to determine a rooting method suitable for a wide range of germplasm. Auxin treatment was required for rooting in most cases. Eighteen of the 50 accessions rooted with a 15 sec. 10 mM indole-3-butyric acid (IBA) dip followed by growth on medium with no growth regulators (NCR). Medium with 10 μM IBA for one week followed by NCR medium produced 12 rooted accessions, but NCR medium alone produced little or no rooting. A 15 sec. dip in 10 mM naphthaleneacetic acid (NAA) followed by NCR medium was tested on 29 accessions which rooted poorly on the other three treatments. Twice as many (28%) rooted on NAA as on either IBA treatment (14% each). Additional treatments combining IBA with darkness or higher temperature were also tested and were successful for some cultivars. P. calleryana, P. koehnei, P. pashia, P. hondoensis, P. ussuriensis, P. betulifolia, P. regelii, P. pyrifolia hybrid cv. Shinseiki and the Pyronia selection failed to root. Twenty two of the 32 P. communis cultivars rooted on at least one treatment.

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Carlos A. Lazcano, Fred T. Davies Jr., Sharon A. Duray, Andres Estrada-Luna, and Victor Olalde-Portugal

Mature cladodes of prickly-pear cactus (Opuntia amyclaea Tenore. cv. Reina) were treated with five wounding methods and four concentrations of potassium salt indolebutyric acid (K-IBA) to stimulate adventitious root formation. K-IBA from 4144 to 41,442 μm (1000 to 10,000 mg·L-1) increased root number and root dry weight; however, root length was decreased at 41,442 μm (10,000 mg·L-1). Root number and root dry weight were higher with wounding methods that had larger wounded surface areas. K-IBA altered rooting polarity and stimulated adventitious root formation along the wounded cladode surfaces. Treatments without suberization had a higher percentage of rotted cladodes. This research validates the commercial practice in Mexico of suberizing cladodes early in the propagation cycle. Auxin application could be of commercial benefit for enhanced rooting in the clonal regeneration of new selections for prickly-pear cactus orchards. The wounding methods and auxin treatments utilized make an excellent classroom demonstration for manipulating rooting polarity.

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April L. Warner and R. Daniel Lineberger

Cotyledon explants and zygotic embryos of Lycopersicon esculentum H132, OH8442, and OH2253 were cultured on Murashige and Skoog medium containing varying concentrations of 2,4-D and NAA with and without 10-7 M zeatin. NAA above 10-5 M and 2,4-D above 10-6 M inhibited root formation from cotyledons. Zygotic embryos were removed from developing ovules at the globular, heart, and torpedo stages and later germinated on hormone-free medium. Globular structures that resembled immature zygotic embryos were produced at NAA concentrations between 10-4 and 10-3 M and 2,4-D concentrations between 10-5 and 10-4 M. Treatments reported to enhance maturation and germination of somatic embryos of other species, including subculture to a hormone-free medium with and without activated charcoal, the addition of an ABA treatment subsequent to the auxin treatment, isolation of individual structures from the explant, and a liquid medium rinse containing activated charcoal, have not been successful in stimulating further development of the globular structures.

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Carole H. Saravitz, Frank A. Blazich, and Henry V. Amerson

Adventitious shoots developed on cotyledons of Virginia pine (Pinus virginiana Mill.) excised from seeds germinated for 3, 6, or 9 days and cultured on media containing 0.5 to 10 mg/liter benzyladenine (BA). Shoot regeneration was greatest (46 shoots per embryo) on cotyledons from seeds germinated for 6 days and placed on medium containing 10 mg/liter BA. Shoots were excised and elongated on medium lacking BA. Following elongation, shoots were placed on media containing 0 to 40 mg/liter indolebutyric acid (IBA) for 14 days followed by transfer to the same medium lacking auxin. Without IBA treatment, percent rooting was 3% and increased to 50% for concentrations of 5 to 40 mg/liter. Rooted shoots averaged 2.0 roots per shoot without auxin treatment, 3.3 roots when treated with 5 mg/liter IBA and root number increased linearly with increased IBA concentration up to 40 mg/liter (4.5 roots). Plant lets were transferred to growing medium and acclimated successfully to greenhouse conditions.