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T.J. Montagno, P.S. Jourdan and S. Z. Berry

Unilateral incompatibility has limited the direction of crossing between L. esculentum and L. hirsutum; the latter can only serve as the pollen parent. In an attempt to introduce the L. hirsutum cytoplasm into L. esculentum, thirty-three somatic hybrid plants have been regenerated following four separate fusions between leaf protoplasts of L. hirsutum PI 126445 and etiolated hypocotyl protoplasts of L. esculentum (`OH7870', `OH832', and `OH8245'). A 33% PEG solution supplemented with 10% DMSO was used as the fusogen. Selection of fusion products was based on treatment of L. hirsutum protoplasts with 1 mM iodoacetic acid and non-regenerability of the L. esculentum genotypes. Hybridity was initially confirmed by intermediate morphology, including leaf shape, type of trichomes, flower shape, stigma placement, and fruit size and color. Isozyme analysis for GOT, PGM, and 6-PDH verified hybridity. Six of the hybrids produced viable seed upon selfing. At least some of the hybrids contained chloroplast DNA from L. hirsutum, indicating that the wild species cytoplasm may be present in these plants.

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T.J. Montagno, S.Z. Berry and P.S. Jourdan

L. hirsutum has been previously reported as recalcitrant to culture and plant regeneration. We have modified tomato protoplasm culture protocols and obtained high frequencies of plant regeneration from leaf protoplasts of L. hirsutum PI 126445, LA 94, and LA 1393, as well as from 8 interspecific hybrids of PI 126445 (male parent) with L. esculentum `Floradade', `Marglobe', `Tropic', `OH7870', `OH7983', `OH832', `OH8243', and `OH8245'. Protoplasts were isolated from 3-week old low light pretreated seedlings and cultured in modified LCM containing 1 mg/L NAA 0.5 m /L BA, and 0.5 mg/L 2,4-D. Cultures were kept in the dark at 30 C, diluted every 3 days with LCM containing only 0.75 mg/L BA and gradually moved to the light. After 2-3 weeks, colonies of 1-2 mm were transferred to solid MS medium containing 0.5 mg/L BA and 0.05 mg/L NAA. Calli containing dark green bud primordia were then placed on MS with 2% sucrose and 2 mg/L zeatin riboside for shoot production.

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Adam F. Newby, James E. Altland, Daniel K. Struve, Claudio C. Pasian, Peter P. Ling, Pablo S. Jourdan, J. Raymond Kessler and Mark Carpenter

Greenhouse growers must use water more efficiently. One way to achieve this goal is to monitor substrate moisture content to decrease leaching. A systems approach to irrigation management would include knowledge of substrate matric potentials and air-filled pore space (AS) in addition to substrate moisture content. To study the relationship between substrate moisture and plant growth, annual vinca (Catharanthus roseus L.) was subject to a 2 × 2 factorial combination of two irrigation treatments and two substrates with differing moisture characteristic curves (MCCs). A gravimetric on-demand irrigation system was used to return substrate moisture content to matric potentials of −2 or −10 kPa at each irrigation via injected drippers inserted into each container. Moisture characteristic curves were used to determine gravimetric water content (GWC), volumetric water content (VWC), and AS at target substrate matric potential values for a potting mix consisting of sphagnum moss and perlite and a potting mix consisting of sphagnum moss, pine bark, perlite, and vermiculite. At each irrigation event, irrigation automatically shut off when the substrate-specific weight of the potted plants associated with the target matric potential was reached. Irrigation was triggered when the associated weight for a given treatment dropped 10% from the target weight. VWC and AS differed between substrates at similar matric potential values. Irrigating substrates to −2 kPa increased the irrigation volume applied, evapotranspiration, plant size, leaf area, shoot and root dry weight, and flower number per plant relative to irrigating to −10 kPa. Fafard 3B had less AS than Sunshine LB2 at target matric potential values. Plants grown in Fafard 3B had greater leaf area, shoot dry weight, and root dry weight. Leachate fraction ranged from 0.05 to 0.08 and was similar across all treatment combinations. Using data from an MCC in conjunction with gravimetric monitoring of the container–substrate–plant system allowed AS to be determined in real time based on the current weight of the substrate. Closely managing substrate matric potential and AS in addition to substrate water content can reduce irrigation and leachate volume while maintaining plant quality and reducing the environmental impacts of greenhouse crop production.