Plantlets of Chrysanthemum x morifolium were grown in vitro either in cellulose plugs (Sorbarods) that were saturated with liquid culture medium or on agar-solidified medium. After transplantation and exposure to an atmosphere of reduced humidity, plantlets in Sorbarods wilted less but transpired more water than plantlets taken bare-rooted from agar. These effects indicated a superior water uptake by the roots in Sorbarods, which was attributed to an increase in number of roots, a reduction in the damage they sustained during transplantation and improved contact between roots and substrate. Various potential advantages in the use of Sorbarods in conjunction with liquid medium are discussed.

Plantlets of Vitis vinifera L. `Moscato Bianco' were grown in vitro in cellulose plugs (Sorbarods) saturated with a modified Murashige and Skoog rooting medium. Both the inclusion of 0.5-l mg paclobutrazol/liter in the rooting medium and the use of culture vessels that reduce the relative humidity from 100% to 94% improved resistance of plantlets to wilting after transplanting. Maximum benefit was obtained with a combination of paclobutrazol and reduced humidity; it resulted in smaller stomatal apertures, shorter stems, reduced leaf area, and more and thicker roots. Chemical names used: (2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl) pentan-3-01 (paclobutrazol).

Greenhouse screening using infested toothpicks was compared to field evaluation of soybean [Glycine max (L.) Merr.) breeding lines for resistance to stem canker disease, caused by southern strains ofDiaporthe phaseolorum (Cke. & E11. (Sacc.) var. caulivora Athow and Caldwell (Dpc). Field screenings are reliable indicators of resistance, but often the disease does not develop naturally in field screening nurseries. Thirty‐seven random F4:6 lines from the cross ‘Hutton’ (susceptible ) ✕ ‘Tracy M’ (resistant) were evaluated for their reaction to Dpc in the field (two locations, 2 yr) under natural infestation and infection conditions, and in the greenhouse (three experiments) with artificial inoculation using infested toothpicks. Our objectives were to compare field and greehouse screening and to determine the usefulness of greenhouse inoculation in predicting the yield and disease reaction of breeding lines when these lines were subjected to natural field infection conditions. Field screening based on symptoms and yield was highly effective in identifying resistant genotypes. Heritabilities for yield and disease ratings in the field were 87 and 92%, respectively. The toothpick inoculation procedure used in the greenhouse was effective with each of three Dpc isolates (different in geographic origin from the field location) in identifying the genotypes that showed highest levels of disease resistance in the field. Phenotypic correlations between greenhouse ratings and yield in the infested field ranged from −0.71 to −0.61. Results indicated that selection based on greenhouse screening can be an effective alternative to field screening when resistance is derived from Tracy M.

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