Nine heat-tolerant tomato [Lycopersicon esculentum (Mill.)] breeding lines, four heat-tolerant cultivars, and four heat-sensitive cultivars were evaluated in the greenhouse under high temperature (39C day/28C night) and in the field. Criteria for heat tolerance included flowering, fruit set, yield, fruit quality, and seed production. Under high-temperature conditions, the group of heat-tolerant lines, the heat-tolerant cultivars, and the heat-sensitive cultivars produced, respectively, the following per plant: flowers, 186, 94, and 55; fruit set 70%, 52%, and 30%; yield, 410, 173, and 11 g; and normal mature fruit, 72%, 37%, and 7%. Yields of heat-tolerant lines under high temperature in the greenhouse ranged from 118% to 31% of their respective yields in the field. Yields of heat-tolerant cultivars were 62% of those in the field. In contrast, yields of heat-sensitive cultivars under high temperature were < 1% of their respective yields in the field. High temperature induced flower abscission, reduced fruit set and yield, and increased the incidence of abnormalities. Major fruit abnormalities with high temperatures included cracks, blossomed rot, watery tissue, and small, immature fruits. Production of viable seeds under the high-temperature regime was severely reduced or totally inhibited regardless of the heat-tolerance level exhibited by the line or cultivar. The failure of heat-sensitive and most heat-tolerant cultivars or lines to produce viable seeds under such a high temperature suggests that a lower level of heat stress than that applied in these experiments could allow the production of enough seeds to test the relationship between heat tolerance in a genotype and its ability to produce viable seeds under high temperature. The results indicate that certain lines have high tolerance to heat and, therefore, could provide valuable sources of plant material for physiological studies to establish the physiological and molecular bases of heat tolerance. Some of the heat-tolerant lines might also serve as excellent germplasm sources in breeding heat-tolerant tomato cultivars.
Aref A. Abdul-Baki
Nicolas C. Strange, John K. Moulton, Ernest C. Bernard, William E. Klingeman III, Blair J. Sampson, and Robert N. Trigiano
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.
Qi Zhang, August C. Gabert, and James R. Baggett
A new sterile mutant designated pollen sterile (PS) found in pickling cucumber (Cucumis sativus L.) is characterized by normal corolla in staminate and pistillate flowers, normal fertility in the female, and absence of pollen in otherwise normal-appearing staminate flowers. All F1 plants from PS × male fertile (MF) sib-matings were MF, and F2 progeny segregated 3 MF: 1 PS. Sib-matings of PS segregates with sister MF segregates produced either 1 MF: 1 PS ratios or all normal plants. Thus, PS is controlled by a single recessive gene. The PS gene is not allelic to apetalous (ap), but was shown to be allelic to male sterile-2 (ms-2) and is designated ms-2 PS. It was not possible to determine possible allelic relationships between ms-2 PS and ms-1 because of strong male and female sterility of the available ms-1 material. F1 generations from gynoecious-PS and monoecious-PS crossed with monoecious, gynoecious (silver-ion treated), and hermaphroditic parents produced no PS plants and sex types did not influence PS levels in F2 progenies, indicating it is not possible to maintain the PS mutants through crosses with different cucumber sex types. It was not possible to change the expression of PS by applying cytokinin, IAA, or GA3, and there were no changes in response to temperature and fertilizer treatment. Unlike gynoecy, which is responsive to some external factors, PS is unresponsive. The results suggest that the use of PS in cucumber F1 hybrid seed production is not practical. Chemical names used: indole acetic acid (IAA), gibberellin (GA3).
Saquib Waheed, Yuan Peng, and Lihui Zeng
In fruit trees, flowering is a key event followed by fruit development and seed production. Gigentea (GI), a clock-associated gene, is known to contribute to photoperiodic flowering and circadian clock control in Arabidopsis thaliana. However, its functions in woody fruit trees remain unclear. In this study, a 2000 bp promoter fragment of the longan (Dimocarpous longan) DlGI gene was isolated from the genomic DNA of longan ‘Honghezi’ by polymerase chain reaction amplification. The DlGI promoter contained two main types of potential cis-acting elements: light-responsive and hormone-responsive elements. The promoter was fused with the β-glucuronidase (GUS) reporter gene of pBI121 to generate the pDlGI:GUS construct. GUS histochemical staining of transgenic A. thaliana revealed that DlGI might play a role in different developmental phases of longan. Exposure of transgenic A. thaliana to varying light intensities showed that the GUS activity increases with increased light intensity. Transient expression of pDlGI::GUS in Nicotiana benthamiana showed that the GUS activity was higher and reached peak a few hours earlier under short-day (SD) than long-day conditions. Exposure to different hormonal treatments revealed that the transcript level of GUS was activated by gibberellin (GA3) and indoleacetic acid (IAA) but suppressed by abscisic acid and methyl jasmonate treatment. In addition, N. benthamiana transient assay and dual-luciferase assay revealed that the presence of early flowering 4 (ELF4) homologs of longan (DlELF4-1 and DlELF4-2) significantly activated the DlGI promoter. The positive response of DlGI promoter to high light-intensity, SD photoperiod, GA3 and IAA signals, and DlELF4 transcription factor suggest that DlGI may function as a circadian clock and play a role in responding to SD conditions and other signals in flower initiation of longan.
Andrew Raymond Jamieson
’ ( right ). Seed Production Plants of ‘Fundy’ and ‘Brunswick’ were established in 1998 in field soil under a tunnel house structure (4.9 × 29.3 m) to investigate seed production. Initially, the structure was divided into four sections to
Daniel J. Cantliffe
hybrid seed production and plant germplasm conservation. The reader has an opportunity to get information, packed into 796 pages, in almost any area related to seeds. The contributing authors to Dr. Basra's book are excellent and well known for their
Karen R. Harris-Shultz, Susana Milla-Lewis, Aaron J. Patton, Kevin Kenworthy, Ambika Chandra, F. Clint Waltz, George L. Hodnett, and David M. Stelly
Zoysiagrass (Zoysia sp.) is used as a warm-season turfgrass for lawns, parks, and golf courses in the warm, humid and transitional climatic regions of the United States. Zoysiagrass is an allotetraploid species (2n = 4x = 40) and some cultivars are known to easily self- and cross-pollinate. Previous studies showed that genetic variability in the clonal cultivars Emerald and Diamond was likely the result of contamination (seed production or mechanical transfer) or mislabeling. To determine the extent of genetic variability of vegetatively propagated zoysiagrass cultivars, samples were collected from six commercially available zoysiagrass cultivars (Diamond, Emerald, Empire, JaMur, Meyer, Zeon) from five states (Arkansas, Florida, Georgia, North Carolina, Texas). Two of the newest cultivar releases (Geo and Atlantic) were to serve as outgroups. Where available, one sample from university research plots and two samples from sod farms were collected for each cultivar per state. Forty zoysiagrass simple sequence repeat (SSR) markers and flow cytometry were used to compare genetic and ploidy variation of each collected sample to a reference sample. Seventy-five samples were genotyped and an unweighted pair group method with arithmetic mean clustering revealed four groups. Group I (Z. japonica) included samples of ‘Meyer’ and Empire11 (‘Empire’ sample at location #11), Group II (Z. japonica × Z. pacifica) included samples of ‘Emerald’ and ‘Geo’, Group III (Z. matrella) included samples of ‘Diamond’ and ‘Zeon’, and Group IV (Z. japonica) consisted of samples from ‘Empire’, ‘JaMur’, ‘Atlantic’, and Meyer3 (‘Meyer’ at sample location #3). Samples of ‘Empire’, ‘Atlantic’, and ‘JaMur’ were indistinguishable with the markers used. Four samples were found to have alleles different from the respective reference cultivar, including two samples of ‘Meyer’, one sample of ‘Empire’, and one sample of ‘Emerald’. Three of these samples were from Texas and one of these samples was from Florida. Three of the four samples that were different from the reference cultivar were university samples. In addition, one sample, Empire11, was found to be an octoploid (2n = 8x = 80). For those samples that had a fingerprint different from the reference cultivar, contamination, selfing, and/or hybridization with other zoysiagrasses may have occurred.
Khin Thida One, Narathid Muakrong, Chamnanr Phetcharat, Patcharin Tanya, and Peerasak Srinives
Jatropha (Jatropha curcas) is one of the most popular tree crops for seed production as a source of oil for biodiesel. However, currently grown cultivars are too large in canopy size and thus have very low harvest index. Alteration of canopy height and size can lead to identification of a desirable plant architecture for jatropha. A study was conducted to determine genetic control of dwarfiness and erect growth habit in jatropha populations derived from an interspecific cross between J. curcas with tall-erect (TL-ER) plant type and J. integerrima with dwarf-spreading (DW-SP) plant type. Crosses were made between both species to develop F1, F2, BC1F1, and BC1F2 generations. The F2 plants segregated at a 1:2:1 ratio for tall (TL), intermediate (ID), and dwarf (DW) plant types as well as for spreading (SP), upright (UP), and erect (ER) canopy angles. Both characters segregated independently producing nine phenotypes including TL-ER, TL-UP, TL-SP, ID-ER, ID-UP, ID-SP, DW-ER, DW-UP, and DW-SP at a 1:2:1:2:4:2:1:2:1 ratio. The BC1F1 (J. curcas × F1) plant segregated into TL-ER, TL-UP, ID-ER, and ID-UP at a 1:1:1:1 expected ratio. Six BC1F2 lines were also evaluated to confirm the results by selfing two trees each of BC1F1 showing TL-ER, TL-UP, and ID-ER growth habits. The progenies of TL-ER trees were all TL-ER; the progenies of TL-UP trees segregated into TL-ER, TL-UP, and TL-SP at an expected 1:2:1 ratio, whereas the progenies of ID-ER trees segregated into TL-ER, ID-ER, and DW-ER at an expected 1:2:1 ratio. The results indicated that dwarfiness and erect growth habit were each controlled by independent genes with incomplete dominant action. The knowledge and progenies obtained from this study can be used in breeding jatropha for desirable canopy size and shape.
Claire H. Luby and Irwin L. Goldman
diversity present in these populations will remain available for use in breeding and seed production into the future, the WI-OSC populations are being released under the Open Source Seed Initiative (OSSI) Pledge, a mechanism developed by OSSI (contact at
Randy G. Gardner and Dilip R. Panthee
Panthee, 2010b ). ‘Mountain Magic’ was tested as NC 05114 in organic and conventional culture from 2005–2007 before being named and released for commercial seed production in 2008. Fig. 1. Pedigree of ‘Mountain Magic’ F 1 hybrid tomato. Description