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Mohamed F. Mohamed, P. E. Read, and D. P. Coyne

Regeneration in vitro from the embryonic axis in Phaseolus sp. has not been reported. Two embryo sizes, 0.3-0.4 mm and 0.6-0.7 mm long at 10-12 and 21 days after pollination, respectively, were excised from 4 P. vulgaris (P.v.) and 2 P. acutifolius (P.a.) genotypes. The embryonic leaves and radicale were removed, and 0.1-0.2 mm of the embryonic axis was cultured on Gamborg's B5 medium with 0, 5, 10 and 20μ MBA. The cultures were incubated in the dark at 25°C for 2 weeks followed by 1 week in continuous cool white light (25μ MS-1m2) before transferring to the second medium (0, 2μ MBA and 2μ MBA + 4μ MGA3). The tissues from the larger embryos initiated a single shoot without PGR in 30% of 1 P.v. explants and 30-60% in 2 P.a. The other 3 P.v. formed roots only. Multiple shoots were initiated in all P.v. (15-60%) and in 2 P.a. (60 and 70%) with 5 or 10μ MBA. The tissues from the smaller embryos had single shoots for all genotypes (30-60%) without PGR. Multiple shoots were initiated in 50-80% and 75-90% of the explants from P.v. and P.a., respectively, with 5 or 10μ MBA. Excess callus formed with 20μ MBA and regeneration decreased. After 3 weeks on the second medium, 6-8 shoot s/P. v. and up to 15-20 shoots/Pa. explants were observed.

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Yan Ma, David H. Byrne, Jing Chen, and Amanda Byrne

Several rose species (Rosa rugosa, R. wichuraiana, R. setigera, R. laevigata, R. banksiae, R. roxburghii, R. odorata and hybrids) were employed to establish the appropriate nutrient media for shoot multiplication and root initiation of cultured shoots and to describe a procedure for the successful transfer to soil of plants obtained in vitro. Cultured shoot tips and lateral buds from different genotypes proliferated multiple shoots on a basal medium (MS salt, vitamins, glycine, sucrose and agar) supplemented with 0mg/l to 6mg/l 6-benzylamino purine (BA) and 0mg/l to 0.5 mg/l naphthalene acetic acid (NAA). Most rose species cultured in a modified MS medium supplemented with 2mg/l BA showed good growth and shoot proliferation. The buds nearest the apex exhibited the slowest rate of bud development. Root development was enhanced and shoot development inhibited by lowering the concentration of MS salts to quarter- and half-strength. With difficult-to-root species, rooting was improved by supplementing the media with auxin or giving them 3-7days of dark treatment.

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James E. Faust and Royal D. Heins

Axillary buds of African violet develop vegetative shoots or reproductive inflorescences. Vegetative axillary development results in a multiple-shoot plant and reduces plant quality. We determined the effect of temperature and plantlet size on axillary bud development. Plantlets were removed from leaf cuttings, graded according to stem diameter, directly stuck into pots 10 cm in diameter, and placed in greenhouses at 18, 22, or 26C. Vegetative development was related to temperature, plantlet size, and nodal position. The number of vegetative axillary shoots per plant decreased from 3.7 to 1.3; that of leaves per vegetative axillary shoot decreased from 10.3 to 4.8 as temperature increased from 18 to 26C. The eight to 10 basipetal nodes developed vegetative shoots or were devoid of axillary development. The percentage of leaf axils in which inflorescences developed increased from 14 on node eight to 100 on nodes 12 and higher. The larger plantlets at the time of transplant had 20% fewer vegetative axillary shoots, whereas reproductive inflorescence development was not affected by plantlet size.

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C.L.H. Finneseth, Desmond R. Layne, and R.L. Geneve

Clonal propagation of pawpaw is currently limited to budding and grafting. A tissue-culture system to rapidly produce clonal material would be valuable for both production and preservation of germplasm. Forced scion wood, shoots from root cuttings, and seedlings were explant sources for ontologically mature, intermediate, and juvenile ages, respectively. Preliminary data indicated that nodal explants had more rapid adventitious shoot formation than shoot tip explants. Disinfestation protocols were developed for each explant source. Nodal explants were cultured on MS medium supplemented with 10 μM BA and 0.1 μM TDZ. Within 3 weeks, 60% of the seedling explants had expanded axillary buds, while no bud expansion was observed for explants of either the intermediate or mature sources. By 6 weeks, seedling axillary shoots had elongated and were suitable for subculture. By 8 weeks, multiple adventitious buds and shoots had formed on all seedling explants. At this same time, axillary shoots began to elongate on intermediate source explants, but mature source explants appeared to be recalcitrant. Explant exudation caused medium darkening, but, by reducing the transfer interval from 4 to 2 weeks, discoloration was minimized. Mature source explants were maintained in culture and after ≈7 months, axillary bud expansion occurred in a small percentage of these explants.

Open access

Mary M. Saam, G.L. Hosfield, and J.W. Saunders

Abstract

A protocol for in vitro propagation was developed with two dry bean (Phaseolus vulgaris L.) cultivars. Shoot cultures were initiated by placing seedling shoot tips (1.0 to 1.5 cm) on Murashige and Skoog (MS) medium in which the effects of kinetin and BA alone or in combination with IAA or NAA were examined with regard to shoot multiplication and root or basal callus formation. The combination of BA (3.0 mg liter–1) and NAA (0.1 mg·liter–1) was most effective in shoot multiplication. At high concentrations of BA or kinetin (>10 mg·liter–1), shoot production and internode elongation decreased markedly and rosette-like cultures with multiple buds developed. Shoots were rooted on basal MS medium. Ramets grew to maturity in the greenhouse or field and produced fertile flowers, pods, and seeds. Chemical names used: N-(2-furanylmethyl)-1H-purin-6-amine (kinetin); N-(phenylmethyl)-1H-purin-6-amine (BA); 1H-indole-3-acetic acid (IAA); 1-naphthaleneacetic acid (NAA).

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R.E. Byers and K.S. Yoder

In 1995, BAS-125W applied at 125 to 500 mg/liter 23 days after full bloom (AFB) to `Starkrimson Delicious'/MM 106 and MM111 reduced average shoot weight and length of the longest shoots in the top and scaffold limbs by 50% at the highest rate. The number of nodes on the lower 40 cm of each shoot was increased by 1.8 times by the growth retardant. The number of pruning cuts, pruning time, and pruning weight per tree was reduce by 30%, 20%, and 29%. Fruit diameter, color, soluble solids, starch, fruit weight, and fruit number per tree were not altered by BAS-125 W. Growth suppression appeared to be greater on trees with heavier crop loads. In 1996, BAS-125W applied at 250 mg/liter 8 days after full bloom was more effective than when applied 19 days AFB to `Starkrimson Delicious'/MM 106 and MM111. Multiple applications of two, three, and four sprays to the same trees at 3-week intervals further reduced shoot growth with each application. Four applications reduced shoot weight by 72%, shoot length by 60%, and basal shoot diameter by 25%, and the number of pruning cuts, pruning time, and pruning weight per tree was reduce by 75%, 55%, and 80%, respectively. Thinning activity of NAA, Sevin, or Accel was not affected by tank mixed sprays with BAS-125W when applied to Gala/M.27 trees 20 days AFB. Tank mixing BAS-125W with combinations of Vydate + Accel or Carbaryl + Accel + Oil did not alter fruit thinning of Fuji/M.27 (at 10 mm fruit diameter). In one experiment, BAS-125 may have potentiated thinning by ethephon and NAA 10 days AFB in another experiment. BAS-125 W sprays at petal fall + 1 and 2 weeks later significantly suppressed % infection by fireblight, Erwinia amylovora, in inoculated shoots. In addition, BAS-125W reduced canker length in the first-year growth in shoots inoculated 2 weeks after treatment.

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Y.L. Qian, M.C. Engelke, M.J.V. Foster, and S. Reynolds

Turfgrass is grown under extremely variable light intensities. This presents difficult management problems, and methods are needed to improve turf performance under variable shade conditions. Two experiments were conducted to determine the influence of trinexapac-ethyl (TE) on turf performance and physiological responses of `Diamond' zoysiagrass [Zoysia matrella (L.) Merr.] under several light intensities. In a polyethylene-roofed greenhouse, `Diamond' was sodded in 12 wooden boxes (1.2 × 1.2 × 0.16 m) (Expt. 1) and 18 fiber containers (55 × 38 × 12 cm) (Expt. 2). Treatments applied to boxes or containers included three levels of shade (40%, 75%, and 88%) with and without multiple TE applications at 48 g·ha-1 of active ingredient. Without TE treatment, vertical shoot growth increased linearly with increasing shade levels. Excessive shoot growth under 75% and 88% shade exacerbated energy depletion, as evidenced by the 45% and 67% lower rhizome mass and the 37% and 65% lower total nonstructural carbohydrate content (TNC), respectively, compared with turf under 40% shade. Trinexapac-ethyl reduced excessive vertical shoot growth and increased rhizome mass and TNC. Mean turf quality was increased by 0.7 and 1.4 units for turf receiving multiple TE applications under 75% and 88% shade, respectively. Trinexapac-ethyl did not increase turf quality or TNC under 40% shade. Canopy photosynthetic rate (Pn) was not affected 4 weeks after the initial TE treatment under any shade level. However, 34 weeks after the initial TE treatment a 50% higher Pn was observed for turf treated with TE under 88% shade, possibly because of higher tiller density. Repeated TE application increased turf quality and provided more favorable physiological responses (such as TNC and Pn) under 75% and 88% shade, where conditions favored vertical shoot growth. However, little or no improvement in turf quality was observed under 40% shade, where conditions favored slow vertical shoot growth. Chemical name used: 4-(cyclopropyl-α-hydroxy-methylene)-3,5-dioxo-cyclohexanecarboxylic acid ethyl ester (trinexapac-ethyl).

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P. Prutpongse and P. Gavinlertvatana

Fifty-four out of 67 species of bamboo tested were successfully propagated in vitro. For nearly every species, multiple shoots were produced from axillary buds on stem node segments cultured on Murashige and Skoog medium containing BA. In a very few species plants could be regenerated adventitiously from callus. This method of propagation was not very efficient or reliable. Rooting occurred in media containing NAA at 2.7 to 5.4 μM. Several species could be stored in vitro on half-strength medium at room temperature > 15 months without transfer. Chemical names used: N6-benzylamino purine (BA); napthyleneacetic acid (NAA).

Open access

A. Altman and R. Goren

Abstract

Morphological changes during development of cultured citrus explants (Citrus sinensis (L.) Osbeck cv. Shamouti) were observed with a scanning electron microscope (SEM). Prophylls of resting buds, covered with epidermal hairs, were closely appressed until the growth of a new shoot; they then expanded. The addition of 10-5 m 6-benzylaminopurine to the medium resulted in the formation of several adventitious buds, surrounded by multiple prophylls, in the axil of the petiole. Abscission of the petiole from the explant involved formation of a separation zone with no evidence of new dividing cells, or active cell division and formation of callus tissue in the abscission zone.

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Logan S. Logendra, Thomas J. Gianfagna, and Harry W. Janes

A mixture of C8/C10 fatty acid methyl esters (FAME) when applied directly and exclusively to leaf axils of greenhouse-grown tomato (Lycopersicon esculentum Mill.) significantly inhibited side shoot development. Plants grown in a single cluster production system in winter produced 8.9 side shoots/plant, whereas those treated with C8/C10 FAME 45 days after sowing, produced only 0.7 side shoots/plant. Total pruning weight of the side shoots was reduced from 40.2 g/plant to 1.3 g/plant. Fruit yield increased 14% with C8/C10 FAME treatment and there was an increase in the harvest index from 0.63 to 0.70. For a spring crop, in which average daily irradiance was more than twice that in winter, overall yield increased 70% when compared to the winter crop. As in winter, side shoot number and side shoot weight/plant were significantly reduced by C8/C10 FAME, but there was no difference in crop yield between C8/C10 FAME and untreated plants. In both winter and spring, untreated plants required hand pruning three times during the production period, whereas C8/C10 FAME-treated plants were pruned only once at the time of application. A C8/C10 free fatty acid (FA) mixture was also applied to one and two-cluster plants with similar results. In the multiple cluster system, application of the C8/C10 FA mixture instead of side shoot pruning reduced plant height and increased yield from 6.4 to 7.4 kg/plant. C8/C10 FA or C8/C10 FAME treatment could be a useful labor saving strategy in greenhouse tomato production and may increase crop yield under conditions in which assimilates may be limited by environmental factors, or as a result of a high level of competition from other fruits or shoots.