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MC.G. Chávez and R. Ferrera-Cerrato

The responses of four micropropagated strawberry (Fragaria × ananassa Duch.) cultivars (`Douglas', `Tioga', `Aiko', and `Pajaro') to colonization by three vesicular-arbuscular mycorrhizal (VAM) fungi were determined under nursery conditions. Species of VAM endophytes were Glomus sp. CPH-23, Glomus macrocarpum Tul. & Tul., and Glomus versiforme Berth & Trappe. Yield in VAM plants tended to exceed that of nonVAM plants during the latter part of the harvest, but VAM effects differed widely with host-endophyte combinations. Cultivar-endophyte combinations producing the best yield were `Douglas'-Glomus sp. CPH-23, `Tioga'- G. macrocarpum, and `Aiko'- G. versiforme. The number of strawberries per plant differed significantly (P < 0.01) for `Tioga', depending on the cndophytes used. Root colonization by the endophytes varied from 25% to 75%. Yield was not related to colonization.

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Jeffrey W. Adelberg, Bill B. Rhodes, Halina T. Skorupska, and William C. Bridges

Adventitious and axillary shoots of melon (Cucumis melo L.) were cultured from explants on a modified Murashige and Skoog medium containing 10 μm BA. Explants were diversified with regard to genetic source (breeding lines Miniloup, L-14, and B-line), seed parts (apical and cotyledon tissue), seed maturity (10-40 days after pollination; DAP), and cotyledon sections with respect to apical-radicle axis (distal and proximal). Plants were screened for ploidy level by pollen morphometry. Immature cotyledons produced more tetraploid regenerants than mature cotyledons from seed of breeding line Miniloup; the highest frequency of tetraploid regenerant plants was from cotyledons of embryos harvested 18 and 22 DAP. Explants from the apical meristem of the same seeds produced fewer or no tetraploid plants. Proximal sections from immature cotyledons of three genotypes (Miniloup, L-14, B-line) produced higher frequencies of tetraploids than whole mature cotyledons or whole immature cotyledons.

Open access

Dennis P. Stimart, Peter D. Ascher, and Harold F. Wilkins

Abstract

Leaf emergence from bulblets of Lilium longiflorum Thunb. generated in vitro from bulb-scale explants incubated in the dark at either 25 or 30°C was enhanced by 3 stimuli: incubation at 4°C for 1 or more weeks after removal from culture; immersion in water at 45° for 30 minutes to 8 hours after removal from culture; or in vitro red-light irradiation. For maximum response, bulblets generated at 25° required longer treatments at either 45° or under red-light irradiation. On the other hand, bulblets generated in vitro at 30° responded least to incubation at 4°. Although all 3 environmental factors ended dormancy, variation in rates of leaf emergence and total percentage of bulblets with leaves at the end of the experiments suggested differences in the state of bulblet dormancy due to in vitro temperature and differences in the physiological action of the environmental stimuli promoting leaf emergence.

Open access

Huan Zhang, Carol Miles, Shuresh Ghimire, Chris Benedict, Inga Zasada, Hang Liu, and Lisa DeVetter

Novamont treatments) applied to tissue culture ‘WakeHaven’ raspberry in Aug. 2017 in northwestern Washington, 2017–19. Mulch laying and field maintenance. Mulches were applied on 10 Aug. 2017 with a custom-built flatbed mulch layer (Corvallis, OR) modified

Open access

Karen M. Templeton-Somers and Wanda W. Collins

Abstract

Six methods of propagating sweet potato (Ipomoea batatas L.), including 3 in vitro propagation methods, nodal propagation, and propagation by slips and cuttings from bedded roots of ‘Jewel’, were evaluated for field performance of the resulting plants and for the degree of plant-to-plant variability. The 2-year experiment (1982 and 1983) included a carryover study with plants obtained from the bedded roots of the first year's study. Plants were evaluated individually for yield, skin and flesh color, mutation frequency, dry matter, and protein content. In both years, plants propagated by stem cuttings and by slips from bedded roots produced higher yields than those propagated by tissue culture methods. Plants propagated by regeneration from cultured leaf explants were consistently lower in yield than plants obtained by all other methods. In the 1983 study, plants from stem cuttings from field-bedded roots significantly out-yielded plants from all other treatments. Stem cuttings from roots bedded in pots in a growth chamber out-yielded all tissue culture propagation methods, even though the tissue-culture explants also were obtained from these same roots. The carryover study showed that all differences in yield due to propagation method were dissipated with a single cycle of the normal propagation method for sweet potato. When yield data were analyzed according to the mother root origin of the plant material, there were significant differences among plants originating from different roots. Differences in skin color mutation frequencies due to propagation method existed in the 1982 study; however, the 1983 study demonstrated that these differences were also due to the origin of the plant material.

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Aref A. Abdul-Baki, S. A. Haroon, and R. N. Huettel

Susceptibility of tomato (Lycopersicon esculentum Mill) genotpyes to the root-knot nematode Meloydogyne incognita and to heat stress can be evaluated in a single labor- and time-saving operation using a nondestructive in vitro excised root technique. Seeds are sterilized and germinated for 2 days on 1% water agar. Five-mm root sections are grown at 28 and 35 C for 30 days on Gamborg-B medium with and without nematode inoculum. Evaluation criteria include fresh and dry weight and the appearance of juveniles, adults, gulls, and egg masses. Evidence will be presented on the breakdown of resistance to M. incognita under high temperature stress.

Free access

Mingbo Qin, Chiwon W. Lee, Alex Y. Borovkov, and Murray E. Duysen

A study was initiated to characterize key enzymes that influence sweetness in carrot (Daucus carota L.) roots. Sucrose synthase (SS), sucrose phosphate synthase (SPS), and UDP-glucose pyrophosphorylase (UDPL) genes were isolated from potato (Solanum tuberosum L.) and cloned in an anti-sense orientation into Agrobacterium tumefaciens Bin19, which has a CaMV 35S promoter. Seedling hypocotyl sections of selected carrot lines were pre-incubated on B5 medium for 2 days, co-cultivated with A. tumefaciens Bin 19 for additional 3 days, and then transferred to a modified B5 medium containing 50 g/mL kanamycin and 400 g/mL carbenicillin. In 4 weeks, 18.6%, 33.3%, and 26.7% of the cultures from a breeding line (W204-C) were found to be transformed, respectively, with SS, SPS, and UDPL as determined by kanamycin resistance. In contrast, no kanamycin-resistant calli were obtained from a commercial cultivar (Navajo) in these transformation studies. The transformed calli proliferated in the medium containing 50 g/mL kanamycin and 400 g/mL carbenicillin, whereas non-transformed calli died in the same medium. These transformed calli are currently being used to regenerate plants via asexual embryogenesis using a suspension culture. The influence of these additional genes on sugar metabolism and accumulation in root tissues of transformed carrots will be characterized in the future.

Open access

E. D. Earle and R. W. Langhans

Abstract

Small (0.5 mm high) shoot tips of Chrysanthemum morifolium ‘Giant #4 Indianapolis White’ were grown on Murashige-Skoog medium containing various levels of kinetin, NAA, and GA3. Formation of roots, single or multiple shoots, plantlets and friable, hard or leafy callus depended on the hormone levels used. Multiple shoots and green leafy callus were produced on medium containing 2.0 mg/l kinetin and 0.02 mg/l NAA. The leafy callus was suitable for subculture and subsequent reorganization of plantlets. Multiple shoots were rooted and grown into normal plants or were used to start new cultures which formed more multiple shoots. This technique will be useful for storage and propagation of Chrysanthemum and especially for detection and rapid multiplication of virus-free plants.