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  • Author or Editor: Virgil Esensee x
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Crosses and self's were made among Fragaria × ananassa Duchn. cv. `Douglas' and `Fern' and Fragaria chiloensis (L.) Duchn. Seeds were surface sterilized, germinated and then grown on MS media (no vitamins, sucrose or hormones) with NaCl concentrations of 0 to 0.5% or 0.5% KCl. Polyethylene glycol (PEG), of corresponding water potentials, was used to induce drought stresses. Whole plant dry weights were evaluated after 50 days. Differences in salt tolerance were associated with genotype; progeny involving crosses with F. chiloensis showed greater salt tolerance. Increases in concentration of PEG caused decreased growth. The use of salt containing media may be used to evaluate strawberry seedlings for salt tolerance and, similarly, PEG may be used to evaluate for drought stress in vitro.

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There is need for backup storage of clonally propagated plant cultivars of numerous taxa. Initial tests, using a protocol developed for dormant apple buds that includes desiccation and slow freezing prior to immersion in liquid nitrogen (-196 C), was not effective with `Valiant' grape. Accordingly, replicates of V. vinifera `Riesling', V. riparia, `Valiant' and a V. amurensis × riparia cross were also tested for survival at –196 C, following desiccation to 25% & 18% water (fwb) and direct immersion into liquid nitrogan. Visual and electrolyte leakage ratings following nine days of dehydration in moist peat were used to assess viability. Direct immersion of desiccated samples resulted in survival for some buds of `Valiant' and a V. amurensis × riparia cross. V. riparia showed some survival when field hydrated and at 25% water, while all buds desiccated to 18% survived. `Riesling' did not survive desiccation, and was killed by all -196 C treatments. The apple protocol was partially effective, in combination with desiccation to 18% in `Valiant' and V. riparia. This is the first report of grape bud survival in liquid nitrogen and more detailed studies are planned.

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Spinach (Spinacia oleracea L.) seed germination can be inhibited by high temperatures. An understanding of thermoinhibition in spinach is critical in predicting germination and emergence events. The purpose of this study was 3-fold: 1) to determine seed germination percentage and rate of spinach genotypes—`Cascade', `ACX 5044', `Fall Green', and `ARK 88-354'—exposed to constant and alternating temperatures; 2) to determine the nature and extent of inhibition imposed by the pericarp; and 3) to investigate leachate and oligosaccharide involvement in thermoinhibition. Germination inhibition began at >20 °C constant temperature and was totally suppressed at 35 °C. Alternating temperatures at 30/15 °C (12-hour day/12-hour night) resulted in greater germination than a constant 30 °C. The genotype sensitivity to supraoptimal temperatures was in the order of `ARK 88-354' ≤ `Fall Green' < `ACX 5044' < `Cascade', but the highly thermoinhibited `Cascade' seeds retained the ability to germinate when shifted to lower incubation temperatures. The pericarp inhibited germination, since seeds deprived of the pericarp had ≈90% germination at 30 °C. `ACX 5044' and `Cascade' had higher ABA content in the pericarp than `ARK 88-354' and `Fall Green'. Before imbibition at 30 °C, raffinose levels in each genotype were in the order of `ARK 88-354' > `Fall Green' > `Cascade'. After 48 hours of imbibition, sucrose and glucose levels were highest and raffinose levels were lowest in `ARK 88-354' and `Fall Green' seeds, while `Cascade' seeds remained less active metabolically. These data suggest that the pericarp apparently acts as a physical barrier as well as a source of inhibitors during thermoinhibition.

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