Roses seeds (achenes) have a reputation of being challenging to germinate due to physiological and minor physical dormancy. The effect of gibberellins (GA) on rose seed germination has generally been neutral or negligible. Soaking rose seeds in cellulase before stratification has been documented to improve germination in some roses, likely due to degrading the outer covering around the embryo to allow for better imbibition. This experiment uniquely combines cellulase with GA to ascertain if there would be a stronger effect of GA if reaching the embryo was a limitation. A full factorial was used with a two-day duration of either dry seed, a 0.5% cellulase soak, or reverse osmosis (RO) water soak followed by a one-day soak of 200ppm GA3, 200ppm GA4 7, 200ppm GA4 7 plus 6-benzyladenine as Promalin®, or RO water. Rosa arkansana was chosen due to it being challenging to germinate. Four replications of 100 seeds each for each of the 12 treatments were prepared and mixed with 80cc of moist peat moss. All treatments were given a common warm stratification (8 weeks room temperature) and cold stratification (12 weeks 4C) followed by constant 10C in a growth chamber. Germination was recorded and germinated seedlings removed three times while at 10C at 5-week intervals. Promalin® led to slightly faster germination at week 5, but by week 10 GA treatments were not significantly different than the water control. Cellulase and RO water pre-GA soaks were not significantly different than each other at any time interval and by week 15 both were significantly better than the dry seed treatment. This data suggests the importance of having well hydrated seeds going into stratification, a neutral effect of GA on germination of this species, suggests 6-benzyladenine may slightly speed along germination, and that cellulase may not significantly improve water penetration over a sufficient imbibition duration.
Native four o’clocks (Mirabilis spp.) are drought-tolerant perennials native to North America, valued for their vibrant flowers and ecological contributions, including pollinator support and soil stabilization. Despite their ornamental appeal and value in ecological restoration, their use in horticulture has been limited due to propagation challenges such as low seed availability, poor germination, and complex dormancy requirements. Micropropagation, the production of new plants from small tissue sections under sterile conditions using artificial media and controlled environments, presents a promising solution to these limitations. It offers a reliable method to produce large quantities of native Mirabilis for conservation and nursery applications. In 2021, an effective micropropagation protocol was developed for the rare North American species Mirabilis macfarlanei. Building on this success, the current project evaluated the applicability of this protocol to three additional native species: Mirabilis greenei, Mirabilis laevis var. villosa, and Mirabilis laevis var. crassifolia. Single-node cuttings were surface sterilized with 20% bleach and cultured on Driver and Kuniyuki Walnut (DKW) medium supplemented with 4 µM 6-benzylaminopurine (BA). All three species were successfully established in vitro and proliferated. Growth parameters, including average number of shoots, shoot length, and shoot dry weight, were compared between DKW with 4 µM BA and Murashige and Skoog (MS) medium with the same BA concentration. For M. greenei, shoot proliferation was similar between MS and DKW (5.7 and 5.8 shoots, respectively). M. laevis var. villosa and M. laevis var. crassifolia produced more shoots on MS medium (10.6 and 4.5) than on DKW (7.8 and 3.9). All species exhibited higher shoot dry weights on MS medium, while shoot lengths were comparable across treatments. Rooting success varied among species. The rooting medium developed for M. macfarlanei (DKW supplemented with 0.5 mg/L indole-3-acetic acid [IAA], 0.5 mg/L naphthaleneacetic acid [NAA], and 0.15 mg/L Sequestrene® 138) was effective only for M. greenei. However, M. laevis var. villosa and M. laevis var. crassifolia rooted better on MS medium containing 1 µM NAA and 0.15 mg/L Sequestrene® 138. Rooted plantlets of all three species were successfully acclimatized in rockwool, with M. laevis var. villosa and M. laevis var. crassifolia flowering under greenhouse conditions.
Bush bean is a popular vegetable as it is high in fiber, vitamins, minerals, and antioxidants. Assessment of the physiological quality of bush bean seeds is essential for ensuring better crop performance and yield, and the controlled deterioration technique is a reliable and practical tool for this purpose. The objective of this study was to determine the seed quality of two bush bean varieties using the controlled deterioration technique. Two bush bean varieties (Jhar Sheem-1 and Jhar Sheem-2) were induced with 12%, 16%, and 20% moisture levels for 0, 4, 8, and 16 days. Seed quality factors, such as, germination percentage, abnormal seedlings percentage, dead seed percentage, soil emergence percentage, root and shoot lengths, and dry matter content, were evaluated. In this study, 24 treatments were arranged as completely randomized design with 3 replications. Both varieties showed an identical performance at 12% moisture in 0 days of the aging period, but prominent differences were noticed at a highly deteriorated level of the factors. The percentage of normal seedlings declined to 85.34% in Treatment-24 (Jhar Sheem-2 at 20% moisture level with a 16-day aging period) compared to Treatment-1 (Jhar Sheem-1 at 12% moisture level with no aging period). Meanwhile, seedling abnormality increased by 22.00% in Treatment-11 (Jhar Sheem-1 at 20% moisture level with an 8-day aging period) relative to Treatment-1. Conversely, root and shoot dry matter were 93.06% and 28.62% lower, respectively, in Treatment-24 than Treatment-1. Moreover, highly remarkable (1%) relations were traced among all the traits, ranging from -0.466 (seed dry matter x abnormal seedling) to 0.983 (normal seedling x root length). Another finding was that among all the values about normal seedlings (i.e., the germination percentage); their affiliation with the soil emergence was prominent, i.e., 0.983. Thus, the outcomes revealed that the controlled deterioration test was highly effective in assessing the physiological conditions of the varieties. According to the vigor and quality performance, bush bean Variety-1 (Jhar Sheem-1) can be used as a parent for hybridization programs to produce superior inherent quality. Future investigations can be conducted to find more acceptable temperature and moisture trait limits among other bush bean varieties.
The University of California Riverside (UCR) rootstock breeding program has selected five advanced avocado (Persea americana Mill.) rootstocks for their resistance to Phytophthora Root Rot (PRR), a major disease affecting avocados worldwide. Another significant threat to avocado trees is laurel wilt (LW), caused by the fungus Harringtonia lauricola. To date, laurel wilt has been reported in 12 states, but has only infected avocado trees in Florida, where it has killed approximately 290,000 trees worth an estimated $95 million. It is anticipated that laurel wilt will eventually spread to California, the leading avocado production region in the U.S., as well as to Mexico and South America, where the largest world-wide avocado production occurs. For the UCR experimental PRR-resistant rootstocks to be successful in the long term after their commercial release, they should positively influence the LW resistance of ‘Hass’ and other scions. In this study, we tested the LW susceptibility and physiological responses of ‘Donnie,’ ‘Hass,’ ‘Gem,’ and ‘Reed’ scions grafted onto UCR advanced clonal rootstocks PP35, PP40, PP42, PP45, and PP80 under climate-controlled greenhouse conditions. All scions were also grafted and tested on ‘Waldin’ seedling rootstock, which is the primary avocado rootstock used in South Florida. Trees of each scion/rootstock combination were either inoculated with H. lauricola or with deionized water as a control. There were six single-plant replicates per treatment for each scion/rootstock combination, arranged in a completely randomized design. Visual disease symptoms were evaluated on a scale of 1 to10 (1= no symptoms, 10 = severe symptoms) every 3 to 4 days from the time of inoculation until the trees were harvested. Physiological variables, including leaf gas exchange (net CO2 assimilation, stomatal conductance, and transpiration), were also measured. At the end of the experiment, all plants were harvested, and the presence or absence of H. lauricola was confirmed by plating stem sections on CSMA (cycloheximide-streptomycin malt agar) medium. Although all scion/rootstock combinations were susceptible to LW, there were differences in susceptibility among combinations. The combinations ‘Hass’/PP45, ‘Gem’/PP40, ‘Gem’/PP80, ‘Hass’/Waldin’, and ‘Gem’/’Waldin’ exhibited the greatest tolerance to LW, as indicated by fewer external symptoms and less reduction in leaf gas exchange variables compared to the other combinations tested. Therefore, these more LW-tolerant scion/rootstock combinations have potential for planting in areas where both PRR and LW diseases occur. The most tolerant combinations identified in this study continue to be evaluated under field conditions for horticultural characteristics and yields in Florida.
Improving stem cutting propagation of grapevine species holds immense importance with the growing interest in grapevine cultivation in the region. Propagating these plants from stem cuttings can be a challenging endeavor. As a result, this research initiative seeks to address this issue by exploring methods to enhance the success rate of stem cutting propagation. By developing more efficient and reliable techniques, nurseries can increase their ability to supply grapevines to local growers, which not only expands the availability of grapevines in the market but also plays a pivotal role in bolstering the wine industry in Mississippi. By facilitating the growth of this industry, improved grapevine propagation methods contribute to economic development, agricultural diversification, and ultimately benefiting the local economy and wine enthusiasts. Hardwood and semi-hardwood cuttings of four bunch grape varieties: ‘Miss Blanc’, ‘MidSouth’, ‘Norton’ and ‘Mamont Noir’ were subjected to 10 hormone treatments of indole-3-butyric acid (IBA) alone and in combination with ascorbic acid. These treatments were applied as a basal quick dip. Sixty days after treatment, rooting percentage, growth index (new shoots), cutting quality (0-5, with 0 = dead and 5 = transplant-ready cutting), total root number, average root length (of three longest roots), and root quality (0-5, with 0=no roots and 5=healthy, vigorous root system) data were collected. Of the four varieties trialed, ‘Miss Blanc’ performed the best with the greatest rooting percentage of 95% as a hardwood cutting and ‘Mamont Noir’ performed the best as a semi-hardwood cutting with the greatest rooting percentage of 100%. ‘MidSouth’ and ‘Norton’ will both require further research to assess the best rooting option for these varieties.
Tea (Camellia sinensis) has the potential to be cultivated as a commercial crop in the United States, but growers need access to clean plant material. The wholesale value of tea in the United States was $13.6 billion in 2022, yet less than 100 acres of tea are currently grown here. Tissue culture can be a means to provide disease-free and genetically identical plants. Three experiments were carried out using explants, which are 2.5 cm stems with single, active nodes from the young shoots of 28-year-old ‘Minto Pacific’ plants. Experiment 1 tested chemo- and thermotherapy: 40 explants were placed in Murashige and Skoog (MS) medium supplemented with 2, 4-dioxo-hexahydro-1-3-5 triazine (2 mL/L), aspirin (1.4 mL/L), and ribavirin (1.5 mL/L). Explants were placed in a growth chamber at 25 ± 1 ℃ on a 16-h photoperiod for 4 to 5 weeks, then subcultured and placed in an incubator for an additional 4 to 5 weeks set at 32 to 35℃ on the high end/light period and 28 to 30℃ on the low end/dark period (alternating every 4 h). All explants were either contaminated or dead, potentially due to high temperatures, by the end of this 8 to 10 week cycle. Experiment 2 evaluated use of meristems, which were excised from axillary buds of the aforementioned young shoots of 28-year-old ‘Minto Pacific’ plants and placed on MS media supplemented with 6-benzylaminopurine (1 mL/L) and gibberellic acid (0.5 mL/L). Explants were placed in a growth chamber at 25 ± 1 ℃ on a 16-h photoperiod. Of the 10 meristems, there was no contamination, but only one meristem has survived long-term (5 months). With Experiment 3, explants (n=26) were soaked in 4% v/v Plant Preservative Mixture (PPM) for 2 h, then transferred to MS medium, before being placed in a growth chamber at 25 ± 1 ℃ on a 16-h photoperiod. Contamination and physiological disorders developed over time, leaving only one visually healthy explant after 5 months. The effect of PPM as a soak or a growth medium-additive needs to be further investigated through additional experiments.
