Vegetative long-shoot buds, greenwood stems, and immature needles of 20-year-old western larch (Larix occidentalis Nutt.) were cultured to induce multiple bud formation. Explants were collected year-round and cultured on a modified Schenk and Hildebrandt (SH) medium containing 6-benzyladenine (BA) at 0, 1, 5, 10, 50, or 100 μm. Multiple buds were produced on buds and stems with terminal meristems, but not on needles or stem sections. The induction of de novo buds and development of axillary buds required BA at 1 to 10 μm; higher concentrations of BA were less effective. More explants formed multiple buds on SH than on modified Murashige and Skoog (MS) media. Multiple buds formed on more buds and stems excised during the growing season than from dormant buds. Buds cultured on media containing gibberellin died within 6 weeks; auxin caused bud elongation but no multiple buds formed. Chemical names used: N-[(trichloromethyl)thio]-4-cyclohexene-1,2-dicarboximide (captan); 6-benzyladenine (BA); 1H-indole-3-butyric acid (IBA); 1H-indole-3-acetic acid (IAA); gibberellin (GA4+7).
E.E. Chesick, D.E. Bilderback, and G.M. Blake
M. J. Davis, Ralph Baker, and Joe J. Hanan
Clonal multiplication of carnation (Dianthus caryophyllus L.) was accomplished in three stages: 1) shoot tip culture initiation stage, 2) shoot multiplication stage, and 3) rooting stage. The culture medium for the initiation stage was examined by comparing various inorganic salt mixtures, vitamin mixtures, carbohydrates, growth regulators, agars, pH’s, and additional supplements for their effect on growth and development of multiple shoots from shoot tips. When shoot tips (ca. 1 mm high) were grown on a modified Murashige and Skoog medium with 10 µM kinetin and 1 µM NAA, apical dominance was counteracted and morphologically normal shoots proliferated rapidly. Transferring these cultures after 4 wk to 100 ml flasks (one per flask) with 50 ml of same medium without agar and supplements, and with the kinetin concentration reduced to 2.5 µM, resulted in an average per original shoot tip of 28 shoots over 2 cm in height being produced in another 3 weeks. These shoots were rooted in BR-8 blocks or Jiffy-7 peat pellets under intermittent mist. Plantlets rooted in these supports were transferred easily to greenhouse conditions. Incorporation of carnation micropropagation into a pathogen-free propagative stock program should not be difficult, and might prove beneficial even if large scale use is limited by economic considerations.
Craig K. Chandler and Arlen D. Draper
N-(3-methyl-2-butenyl)-1H-purin-6-amine (2iP) has been used to promote multiple shoot formation in previous tissue culture studies with ericaceous plants (1, 3-7). Fordham et al. (3), however, found that (E)-2-methyl-4-(1H-purin-6-ylamino)-2-buren-1-ol (zeatin) was the most effective cytokinin for stimulating shoot proliferation of cultured Exbury azalea (Rhododendron sp.). This study was conducted to determine if highbush blueberry is similar to Exbury azalea in its response to zeatin.
Anne E. Sama and Harrison G. Hughes
Shoot tips, approximately 3-5mm, were isolated from corms of young greenhouse-grown plants of cocoyam, cultivar South Dade White. After preliminary evaluations, the initiation media evaluated were B5 basal salts supplemented with 0.05 μM NAA with 5μM BAP, 20μM BAP or 2μM TDZ. The above media were in the form of liquid medium in flasks on a rotary shaker, liquid medium with filter paper bridges, stationary liquid medium without filter paper and solidified medium with 0.4% agar. TDZ stimulated greater growth with multiple shoot formation. Liquid media either in the shaker or stationary form were more effective in terms of growth. Shoots were subsequently evaluated for multiplication with 1μM TDZ and 5μM BAP with 0.05μM NAA producing greater shoot numbers. Over 30 plants have subsequently been rooted and acclimatized under mist or humidity tent.
M.K. Ehlenfeldt, A.W. Stretch, and V. Brewster
The resistance of 48 highbush blueberry cultivars and selections to the blight phase of mummy berry disease, incited by the fungus Monilinia vaccinii-corymbosi (Reade) Honey, was examined in relation to percent Vaccinium angustifolium Ait. ancestry, season of fruit maturity, and shoot growth during the primary infection phase. Correlations of percent blighting with percent V. angustifolium ancestry were significant across 3 years, but correlations with fruit maturity were significant in only 2 of 3 years. Correlations of percent blighting with early shoot growth were significant in both years measured, with r values of 0.54 in 1994, 0.83 in 1995, and 0.83 across years. A multiple regression found only shoot growth highly significant for susceptibility and rendered V. angustifolium ancestry and season of fruit maturity nonsignificant. Resistant cultivars exhibiting early shoot elongation suggest that resistance can be either biochemically or escape based.
Chi Won Lee and John C. Thomas
Shoot tips and stem nodes of Asclepias erosa Torr., cultured on a modified (0.5 × major salts) Murashige and Skoog (MS) medium containing 0.54 µm (0.1 mg/liter) NAA and 44.4 µm (10 mg/liter) BA, produced multiple shoots in 5 weeks. Subcultures of the individual shoots on the same medium produced 5-12 new shoots 4 weeks later. Rooting of the resultant shoots was best accomplished by preculturing them for 48 hr on MS medium containing 246 or 492 µm (50 or 100 mg/liter) IB A prior to subculturing for 4 weeks on MS medium devoid of growth regulators. The rooted cultures were established successfully in soil. Chemical names used. NAA: 1-naphthaleneacetic acid. BA:N-(phenylmethyl)-lH-purin-6-amine. IBA: lH-indole-3-butanoic acid.
Michael E. Kane and Charles Lane
Many wetland plant species used for aquascaping and wetland revegetation projects are collected from donor wetland sites for planting elsewhere. Increased demand for wetland plants has lead to over-collection and subsequent environmental damage to these donor sites. Micropropagation provides an ecologically sound alternative to field collection and allows for production of under utilized wetland species and genotypes that are either slow-growing or difficult to propagate using conventional methods. Sagittaria latifolia Willd. (Duck-potato), a rhizomatous herbaceous wetland species, was established in vitro from surface-sterilized lateral and terminal rhizome shoot-tips cultured in liquid basal medium consisting of half-strength Murashige and Skoog mineral salts, 0.56 mM myo-inositol and 1.2 μM thiamine supplemented with 87.6 mM sucrose. Prior to multiplication, responsive Stage I cultures were indexed for cultivable bacteria and fungi. Shoot multiplication occurred in vitro through formation of multiple node rhizomes bearing terminal shoots. Duck-potato exhibited a high sensitivity to relatively low benzyladenine (BA) levels. Maximum rhizome and shoot production occurred from single shoot explants initially cultured on agar-solidified BM supplemented with 4.0 μM BA for 28 days. However, repeated subculture on BM supplemented with greater than 2.5 μM BA resulted in increased mortality, reduction in multiplication rate, or production of dormant corms. Consistent shoot multiplication (four to five shoots/explant) was possible in the presence of 1.5 μM BA. Maximum (100%) acclimatization and rooting was attained by direct sticking of Stage II microcuttings in soilless growing medium contained in 38 cell plugs. Production of salable plants bearing multiple rhizomes was possible within 6 weeks post-transplant. Preliminary observations indicate that corm formation in Sagittaria latifolia may be mediated by photoperiod.
John M. Ruter
A study was conducted with Prunus × incamp `Okame' to evaluate the effects of a pot-in-pot production system compared to a conventional above-ground system and cyclic irrigation on plant growth and water loss. Plants were grown in #7 (26-L) containers with a 8:1 pinebark:sand (v/v) substrate. Cyclic irrigation provided the same total volume of water, but was applied one, three, or four times per day. Final plant height and stem diameter, shoot and root dry weight, total biomass, and root:shoot ratio were all increased for plants grown pot-in-pot compared to above-ground. Multiple irrigation cycles increased stem diameter, shoot dry weight, and total biomass, compared to a single irrigation application. Multiple irrigation cycles decreased the root:shoot ratio. Evapotranspiration was influenced by production system, irrigation, and date. Amount of water lost as leachate was influenced by irrigation and date. Cyclic irrigation resulted in a two-fold decrease in leachate volume. Soluble salts and nitrate-nitrogen in the leachate were influenced by an interaction between production system, irrigation, and date.
Maritza I. Tapia and Paul E Read
It has been previously demonstrated that thidiazuron (TDZ) enhanced the regeneration and multiple shoot proliferation of vinifera grape cultivars. To determine the effect of TDZ on the multiplication of hybrid grapes, in vitro nodal segments from cultivars Chancellor, Leon Millot, and Valiant were cultured on MS medium supplemented with 0, 0.01, 0.05, 0.1, 0.5, and 1.0 mg TDZ/liter. After 1 month, the higher percentage of rooted shoots was obtained from the explants cultured in medium containing the lowest concentration of TDZ (0.01 mg–liter–1) independent of the genotype. Multiple shoot proliferation was favored by high concentrations of TDZ (0.5 and 1.0 mg–liter–1). An average of 0.39 and 0.39 shoots, respectively, was obtained from `Chancellor' cultures, 0.56 and 0.59 from `Leon Millot', and 1.93 and 2.38 from `Valiant'. Vitrification and teratological structures were observed in all the cultures of the three genotypes, but less vitrification occurred in `Valiant' plantlets.
Kimani Waithaka, Albert C. Hildebrandt, and Malcolm N. Dana
In vitro cultures were used to study the development of axillary bud and stolon tip explants of cultivated strawberry (Fragaria × ananassa Duch.). Explants cultured on Murashige-Skoog basal media containing kinetin at 1, 5, or 10 mg/liter developed into leafy shoots. Low concentration of kinetin (1 mg/liter) promoted the development of both types of explants into single shoots while higher concentration (10 mg/liter) promoted production of multiple leafy shoots developing from axillary buds of the earlier formed leafy shoots. NAA at 1 mg/liter promoted callus growth from both types of explants. Axillary bud explants developed into stolons when cultured on media containing gibberellic acid (GA3) at 5, 10 or 20 mg/liter. Stolon apices developed into leafy shoots while the second axillary stolon buds of the tips were inhibited when the explants were cultured on GA3-containing media. Combinations of GA3 and kinetin induced the development of axillary bud explants into structures intermediate in form between those of stolons and leafy shoots. Stolon apices and stolon axillary buds at the stolon tips developed into leafy shoots and continuing stolons, respectively, when the explants were cultured on a kinetin-containing medium for one week, and then transferred onto a GA3-containing medium. Thus, the developmental pathway of axillary strawberry buds was shown to be responsive to a balance between GA and cytokinins following removal from apical dominance.