Search Results

You are looking at 1 - 6 of 6 items for

  • Author or Editor: C. Bernard x
Clear All Modify Search

Abstract

One of the most important decisions a grower makes when formulating plans for planting is what cultivar to select. The experienced grower has observed the evolution of cultivars and is intensely aware of the vast improvements that have been made through plant breeding. Much of the increase in crop productivity can be attributed to the disease resistance, environmental adaptability, and increased yield potential incorporated into cultivars by public and private plant breeders.

Open Access

Abstract

Celery (Apium graveolens L.) seeds germinated at 10°C for 14 days produced shorter and more uniform radicles (0– mm) than seeds germinated for 8 days at 24° (0–10 mm). Removal of seed leachates improved the germination of celery seeds in the light. Celery seeds germinated at 10° prior to sowing emerged faster, and produced more uniform plants than those not pregermihated, and were not thermodormant when incubated at 32°.

Open Access

One hundred twenty-eight field samples of 25 potato stem sections were analyzed for detecting bacterial ring rot (BRR). Samples containing more than 105, between 105 and 104, and <104 immunofluorescing BRR cells per milliliter of sample, detected using immunofluorescence-antibody staining with MAb9A1, were used to compare the efficiency of two other detection methods. Samples were screened with a digoxigenin-labeled DNA probe (Bh1 2, 0.6 kbp) detected by chemioluminescence on nylon membrane. Samples also were screened with a PCR test using primers derived from the sequence of the Bh12 probe. DNA probe tests on these three bacterial concentrations showed a detection efficiency of 100%, 76.8%, and 8.0%, respectively, whereas detection efficiencies of 100%, 100%, and 84.5% were obtained with PCR tests. Almost all positive samples gave the expected 403 bases ethidium-bromide-stained band when the amplified products were analyzed on 1.4% agarose gel. Thus, the PCR test was a sensitive detection method for screening bacterial ring rot of potato.

Free access

Abstract

Forty-seven enzymes and general protein of fruit, seed, and cotyledons of Cucumis sativus L. var. sativus and var. hardwickii (Royle) Kitamura were examined by horizontal starch gel electrophoresis to provide information on enzyme activity, stability, resolution, and variability. Of the 5 extraction buffers tested, a Tris base/Tris HC1 buffer at pH 7.1 provided consistent, clear resolution of the enzymes tested. Further studies of several enzymes revealed: 1) 30% DMSO buffer extended the storage life of phosphogluconate dehydrogenase (PGD); 2) the appearance of additional bands to glucosephosphateisomerase (GPI) and disappearance of bands from PGD zymograms occurred when extracts were stored for 7–8 days at 10°C; 3) the zymogram patterns of glutathione reductase (GR), isocitrate dehydrogenase (IDH), malate dehydrogenase (MDH), and phosphoglucomutase (PGM) were not affected under this storage regime; and 4) zymograms of cotyledonary tissue of seedlings grown under flourescent light in either a 9 or 12 hr light photoperiod at 30°/26° and 22°/18° day/night temperatures for 14 days then stored for 120 days at –18° were similar to fresh extracts. Polymorphisms were observed in GPI, GR, IDH, peptidase, PGD, and PGM. No variety specific electromorphs were observed between hardwickii and sativus, thus supporting the conspecific hypothesis regarding these 2 varieties. Twenty-four of 46 plant introductions and 5 of 11 inbred lines were variable for 1 or more of the 6 polymorphic isozymes.

Open Access

Detailed information on the geographic distribution of a crop is important in planning efficient germplasm conservation strategies but is often not available, particularly for minor crops. Using germplasm collection data from Kenya, Tanzania, and Uganda, we used distribution modeling to predict the distribution of sweetpotato [Ipomoea batatas L. (Lam.)] in sub-Saharan Africa. We used a consensus modeling approach using the following algorithms: genetic algorithm for rule set prediction (GARP), maximum entropy, BIOCLIM, and DOMAIN. The predicted distribution encompasses known sweetpotato production areas as well as additional areas suited for this crop species. New geographic areas where at least three models predicted presence were in Angola, Cameroon, Central African Republic, The Congo, Democratic Republic of Congo, Gabon, Ghana, Angola, Ethiopia, Mozambique, Rwanda, and the Central African Republic. This information can be used to fill gaps in current sweetpotato germplasm collections as well as to further enhance the current presence-only based distribution model. Our approach demonstrates the usefulness of considering several models in developing distribution maps.

Free access

Helianthus verticillatus Small (whorled sunflower) is a federally endangered plant species found only in the southeastern United States that has potential horticultural value. Evidence suggests that H. verticillatus is self-incompatible and reliant on insect pollination for seed production. However, the identity of probable pollinators is unknown. Floral visitors were collected and identified during Sept. 2017 and Sept. 2018. Thirty-six species of visitors, including 25 hymenopterans, 7 dipterans, 2 lepidopterans, and 2 other insect species, were captured during 7 collection days at a site in Georgia (1 day) and 2 locations in Tennessee (6 days). Within a collection day (0745–1815 hr), there were either five or six discrete half-hour collection periods when insects were captured. Insect visitor activity peaked during the 1145–1215 and 1345–1415 hr periods, and activity was least during the 0745–0845 and 0945–1015 hr periods at all three locations. Visitors were identified by genus and/or species with morphological keys and sequences of the cox-1 mitochondrial gene. The most frequent visitors at all sites were Bombus spp. (bumblebees); Ceratina calcarata (a small carpenter bee species) and members of the halictid bee tribe Augochlorini were the second and third most common visitors at the two Tennessee locations. Helianthus pollen on visitors was identified by microscopic observations and via direct polymerase chain reaction of DNA using Helianthus-specific microsatellites primers. Pollen grains were collected from the most frequent visitors and Apis mellifera (honeybee) and counted using a hemocytometer. Based on the frequency of the insects collected across the three sites and on the mean number of pollen grains carried on the body of the insects, Bombus spp., Halictus ligatus (sweat bee), Agapostemon spp., and Lasioglossum/Dialictus spp., collectively, are the most probable primary pollinators of H. verticillatus.

Open Access