Considerable differences exist in the tolerances of onion inbreds to CIPC. Inbreds derived from ‘Iowa Yellow Globe’ were the most tolerant among the inbreds evaluated. Seedlings grown in the laboratory on agar containing the herbicide responded similarly to treated plants in field plots. The laboratory technique provides a fast, efficient method of screening large numbers of inbreds under controlled conditions.
Seedstalk height of carrot (Daucus carota L.) was reduced as the post-vernalization temperature increased from 15/21° to 27/32°C (night/day) with no significant effect on flowering and seed formation. Seedstalks of ‘Royal Chantenay ’ carrot were most affected by the high temperatures and ‘Scarlet Nantes’ were the least affected while ‘Danvers 126’ was intermediate. Few plants had macroscopic seedstalk development 6 weeks after vernalization although the temperature during this period had a permanent influence on ultimate seedstalk height. Carrots grown at 27/32° during the initial 6 weeks following vernalization and then transferred to the optimum 15/21° grew no taller than plants held at 27/32°. Vernalization temperatures of 0°, 5°, and 10° for 10 weeks did not affect the percentage of plants flowered, time of bolting, or rate of seedstalk elongation. Ultimate seedstalk height was reduced only in ‘Royal Chantenay’ vernalized at 10°. Flowering was decreased by post-vernalization temperatures of 27/32° and 2l/27°C when carrots were stored only 5 weeks at 5° but not, after storage for 10 weeks or more. Increasing the vernalization time to 10 weeks hastened the rate of bolting in all three cultivars and increased ultimate seedstalk height in only ‘Royal Chantenay’ and ‘Danvers 126.’ Temperature during the first year of root growth, foliage removal from mature roots prior to storage, and photoperiod following vernalization did not affect seedstalk elongation or flowering.
Flowering of rhubarb (Rheum spp.) was affected by plant age and vernalization temperature and by vernalization time in young crowns. Year-old crowns flowered after storage at 0°C or 5°C for 3 months or more. All 19 week-old crowns flowered after storage at 0°C for 3 months or more and some flowered after storage at 5°C. The 16 week-old crowns flowered only after 4½ and 6 months storage at 0°C. None of the 13 week-old crowns flowered. There was no flowering of crowns stored at 10°C regardless of age or length of storage. Growing temperature and photoperiod following vernalization did not influence flowering.
Reaction to Xanthomonas phaseoli (E.F. Smith) Dowson, cause of common blight disease in beans, Phaseolus vulgaris L., was inherited quantitatively in the cross early flowering susceptible cv. Great Northern (GN) 1140 × late flowering tolerant line ‘GN Nebr. #1, sel. 27’. F1 populations showed partial dominance for susceptibility at 25 days and nearly complete dominance at 43 days after inoculation. Genes controlling delayed flowering, under long photoperiod and high temp, and tolerant reaction were linked. Early, blight tolerant advanced lines were not obtained by pedigree selection. They were obtained, however, by the backcross method, using ‘GN Nebr. #1, sel. 27’ as the recurrent parent. Different photoperiod × temp regimes in growth chambers induced flowering at the same or different times in nearly-isogenic lines of the same age. Vegetative plants exhibited higher levels of tolerance and lower bacterial populations than did plants in the pod stage. The bacterial population in susceptible ‘GN 1140’ was higher than in early and late tolerant lines.