Method for spore production of Leptosphaeria maculans

To enable the epidemiology of Leptosphaeria maculans a pathogen of brassicas to be studied a method for producing spores was required Sporulation of L maculans was assessed on V8juice agar and PDA under two light conditions Five L maculans isolates subcultured with three replicates on each agar were incubated under continuous cool white fluorescent lights at room temperature or 1212 h lightdark at 20C After 9 days incubation colony diameter was measured and spores counted Spore suspensions were produced by pouring 10 ml of sterile water onto each colony and scraping the surface with a sterile glass rod and spores counted using a haemocytometer For all isolates colony diameter was greater on V8juice agar (372526 mm) compared to PDA (123501 mm) under both conditions Isolates subcultured on V8juice agar (979106/plate) gave a higher spore concentration than PDA (355105/plate) Light condition significantly affected spore production but not colony diameter as the highest spore suspension concentration was obtained from those isolates subcultured on V8 juice agar under continuous cool white fluorescent at room temperature (186107/plate) while the lowest concentration was obtained from isolates subcultured on PDA at 20C with 1212 h lightdark (900104/plate) The results have determined the best method for spore production for subsequent experiments

Number of Open Florets on a Flowering Stem Influences Postharvest Life of Antirrhinum majus L.

Flowering stems from three commercial inbreds and their F1 hybrids of Antirrhinum majus L. were cut when the first eight basal florets opened. Tops of the stems were removed above the eighth floret and florets were removed leaving two, four, six, or eight open florets on a stem. A completely random design with 10 replications was used. Flowering stems were placed in plastic storage containers 35 × 23 × 14 cm (L × W × H) with 2.5 L deionized water for postharvest evaluation. Evaluation took place under continuous cool-white fluorescent light (9 μmol·m–2·s–1) at 24°C Postharvest life was determined as the number of days from cutting to discard when 50% of the open florets on a flowering stem wilted, turned brown, or dried. Results showed postharvest life increased as the number of open florets on a stem decreased. Mean postharvest life increased as much as 4.7 days when only two florets remained on a stem. These results indicate a direct relationship between number of florets on a cut flower stem and postharvest life.

OPTIMIZING CALLUS INITIATION USING STOLON NODAL SEGMENTS OF BUFFALOGRASS NE84-609 AND A RESPONSE SURFACE DESIGN

The concept that greater callus mass will induce competence was investigated. The second most immature nodal segments were removed from heavily fertigatcd greenhouse grown plants. Shoots initiated from those nodes were only cut back to one-third their total length. They were subjected to the following treatments: (1) dicamba from 1μM to 5μM in increments of 1.0; (2) B5 medium salt concentrations from 1/3x to 5/3x in increments of 1/3; (3) sucrose levels from 2% to 10% in increments of 2; (4) casein hydrolysate from 0 to 200mg/l in increments of 50. The experiment consisted of twenty-five different treatment combinations in a central composite rotatable second order design. Explants were placed in continuous cool white fluorescent light at 26°C. Dicamba, B5 salts, and sucrose had significant effects on callus mass (p<.12), while casein hydrolysate had no notable effects on callus mass (p ≥ .57). It was determined that optimum response occurred at 5/3x concentration of B5 salts, 10% sucrose, and 5.0μM dicamba. White, compact calli were observed in treatment combinations that yielded callus fresh weights of two-hundred milligrams or higher.

PLANT REGENERATION IN VITRO FROM THE EMBRYONIC AXIS OF COMMON AND TEPARY BEANS

Regeneration in vitro from the embryonic axis in Phaseolus sp. has not been reported. Two embryo sizes, 0.3-0.4 mm and 0.6-0.7 mm long at 10-12 and 21 days after pollination, respectively, were excised from 4 P. vulgaris (P.v.) and 2 P. acutifolius (P.a.) genotypes. The embryonic leaves and radicale were removed, and 0.1-0.2 mm of the embryonic axis was cultured on Gamborg's B5 medium with 0, 5, 10 and 20μ MBA. The cultures were incubated in the dark at 25°C for 2 weeks followed by 1 week in continuous cool white light (25μ MS-1m2) before transferring to the second medium (0, 2μ MBA and 2μ MBA + 4μ MGA3). The tissues from the larger embryos initiated a single shoot without PGR in 30% of 1 P.v. explants and 30-60% in 2 P.a. The other 3 P.v. formed roots only. Multiple shoots were initiated in all P.v. (15-60%) and in 2 P.a. (60 and 70%) with 5 or 10μ MBA. The tissues from the smaller embryos had single shoots for all genotypes (30-60%) without PGR. Multiple shoots were initiated in 50-80% and 75-90% of the explants from P.v. and P.a., respectively, with 5 or 10μ MBA. Excess callus formed with 20μ MBA and regeneration decreased. After 3 weeks on the second medium, 6-8 shoot s/P. v. and up to 15-20 shoots/Pa. explants were observed.

Artificial Light Enhances Red Pigmentation, but Not Ripening, of Harvested `Anna' Apples

Mature-green `Anna' apples (Malus domestics Borkh.) reddened after harvest as a result of exposure to continuous cool-white fluorescent light. Color development was most rapid at 20C but most intense at 13C. At 2C, although the induction of red pigmentation was the slowest, a 72-hr exposure rendered color not significantly different from that of red, commercially harvested fruit. The development of color was light-intensity dependent, approaching saturation at 14.5 W·m-2 (at 13 C). No differences in fruit ripening were found between fruit that developed color under artificial light and red fruit from the commercial harvest, in spite of some stimulation of ethylene production during illumination.