Experiments were conducted to establish an efficient protocol of micropropagation of Beaucarnea gracilis and B. recurvata two endemic and endangered Mexican species. Multiple shoots were induced by direct organogenesis from in vitro seedlings and longitudinal sections of seedlings in both species. The highest formation of shoots per explant, both B. gracilis and B. recurvata, was obtained from longitudinal sections of seedlings on Murashige and Skoog (MS) medium supplemented with 22.2 μm 6-benzylaminopurine, induced 8.2 and 11.1 shoots per explant respectively. In vitro rooting was readily achieved on MS medium with 1 g/l activated charcoal without growth regulators. According to initial treatment and depending on where the shoots come from, the rooting rates were 61% to 100% for B. gracilis, and 83% to 100% for B. recurvata. Survival rates in greenhouse conditions for both species were 80% to 100% after 3 months. These results indicate that the micropropagation of these species of Beaucarnea is technically feasible, and that in vitro culture is a useful option for the conservation and propagation of these important endangered species.
Abstract
Field and greenhouse experiments were conducted to study the relationships among plant growth traits; ratios of dry weights among nodules, roots, and shoots; and traits associated with N2-fixation potential of common bean (Phaseolus vulgaris L.). The dry weights of plant parts and the traits associated with N2-fixation differed among the 10 lines studied. A visual nodulation score used to evaluate N2-fixation potential was correlated positively with nodule dry weight, acetylene reduction (AR) value, root dry weight, and shoot dry weight for plants grown under both greenhouse and field conditions. AR values, nodule dry weight, and visual nodule scores of plants grown in the greenhouse were correlated positively with the respective figures obtained for field-grown plants. These methods of evaluation can be used to discriminate among lines for N2-fixation potential.
Selected physical properties of 13 coconut coir dusts from Asia, America, and Africa were compared to physical properties of sphagnum peat. All properties studied differed significantly between and within sources, and from the peat. Coir dusts from India, Sri Lanka, and Thailand were composed mainly of pithy tissue, whereas most of those from Costa Rica, Ivory Coast, and Mexico contained abundant fiber which was reflected by a higher coarseness index (percentage by weight of particles larger than 1 mm in diameter). Coir dust was evaluated as a lightweight material, and its total porosity was above 94% (by volume). It also exhibited a high air content (from 24% to 89% by volume) but a low easily available and total water-holding capacity which ranged from <1% to 36% by volume and from 137 to 786 mL·L–1, respectively. Physical properties of coir dust were strongly dependent on particle size distribution. Both easily available and total water-holding capacity declined proportionally with increasing coarseness index, while air content was positively correlated. Relative hydraulic conductivity in the range of 0 to 10 kPa suction dropped as particle size increased. Coir dusts with a particle size distribution similar to peat showed comparatively higher aeration and lower capacity to hold total and easily available water. An air–water balance similar to that in peat became apparent in coir dust at a comparatively lower coarseness index (29% vs. 63% by weight in peat). Stepwise multiple regression analysis showed that particles with diameters in the range of 0.125 to 1 mm had a remarkable and highly significant impact on the physical properties studied, while particles <0.125 mm and >1 mm had only a slight or nonsignificant effect.
In this work, we present the study of the behavior of 15 tomato cultivars under different grow lights to evaluate the quality of seedlings in the production system. The lamps used are: compact fluorescent, high-efficiency fluorescent, fluorescent, and pure blue light-emitting diodes (B-LEDs). The trial was carried out in a culture chamber with the temperature and relative humidity continuously controlled. Spectral radiation was measured at the canopy level. The following were quantified: fresh, dry biomass partitioning organs (leaves, stems, and roots), the total dry weight/total fresh weight relationship, shoot/root ratio, and indole acetic acid. We found high-efficiency fluorescent light treatment has a very interesting spectral quality for all cultivar applications as a result of it having the lowest photosynthetically active radiation (PAR):near infrared (NIR), blue:red (B:R), blue:far red (B:FR), and red:far red (R:FR) ratios; ‘Conquista’, ‘Velasco’, and ‘Lynna’ are cultivars that show sensitivity to special wavebands (ultraviolet, B, R, and FR). ‘Ikram’, ‘Saladar’, and ‘Delizia’ tolerate the lack of minimum energy and spectral quality.
A wide range of water-treatment technologies is used to control waterborne microbial problems in greenhouse and nursery irrigation. An online modified Delphi survey was carried out to identify the perceived key attributes that growers should consider when selecting among water-treatment technologies and to characterize a list of 14 technologies based on those same attributes. The expert panel consisted of ornamental plant growers (n = 43), water-treatment industry suppliers (n = 28), and research and extension faculty (n = 34). The survey was delivered to the expert panel in two rounds. Response rate was 59% and 60% for the first and second rounds, respectively. Growers identified control of plant disease, algae, and biofilm as primary reasons for adopting technologies, whereas mandatory regulation was not a major reason for adoption. All 23 attributes (related to cost, system size, control of microorganisms, chemistry, ease of use, and regulation) were perceived to be important when selecting between water-treatment technologies. Injectable sanitizing chemicals such as chlorination were considered to have low capital cost, unlike technologies that required installation of more complex equipment, such as heat treatment, hydrogen peroxide, ozone, reverse osmosis, or ultraviolet radiation. Filtration (excluding membrane filtration) was the only technology not perceived to be effective to control microorganisms. Filtration and copper were not considered effective to control human food-safety pathogens. Ozone was rated the highest as a technology that removes or oxidizes agrochemicals. Chemical water treatments, as opposed to physical water treatments, were perceived to be sensitive to water quality parameters and to have residual effect through the irrigation. Chlorine gas was perceived to be the only technology for which regulatory permission would be an obstacle. All technologies were perceived to be effective in water with low electrical conductivity (EC) or in solutions containing water-soluble fertilizers. This survey documents perceived attributes of water-treatment technologies, which are most useful where experimental data are not yet available. Research and outreach needs were highlighted by cases where perceived attributes differed from available experimental data or where there was a lack of consensus between experts.
The genes sugary1 (su1) and shrunken2 (sh2) are commonly used to produce sweet and super-sweet corn (Zea mays L.), respectively. In this work we compare corn borer [european corn borer (ECB) (Ostrinia nubilalis Hbn.) and pink stem borer (PSB) (Sesamia nonagrioides Lef.)] susceptibility in seven pairs of su1 and sh2 near-isogenic sweet corn inbreds (101t, C23, C40, C68, Ia453, Ia5125, and P39) and the relationship between corn borer resistance and vegetative phase transition. The seven pairs of near-isogenic inbreds were evaluated under corn borer infestation during 3 years in northwestern Spain. Differences among inbreds were significant for most of the traits, although resistance was partial. Ia5125su1 and C40su1 were the most resistant inbreds. Differences between a few pairs of near-isogenic su1 and sh2 strains were significant for some vegetative phase change and corn borer damage-related traits. Generally su1 strains flowered earlier, had a shorter juvenile phase, fewer PSB, and more ECB larvae than sh2 strains. However su1 and sh2 strains did not differ significantly for most traits related to phase transition and corn borer damage; notably ear damage was not significantly different between su1 and sh2 strains. These results suggest that theoretical and practical results of sweet corn (sugary1) breeding for corn borer resistance could be capitalized for super-sweet corn (shrunken2) breeding.
Field corn (Zea mays L. var. mays) cultivar heterosis could improve sweet corn (Zea mays L. var. rugosa Bonaf) heterotic patterns. Two Spanish field corn (Su) and two sweet corn (su) heterotic patterns have been reported previously. The objective of this study was to determine which sweet × field corn crosses could be used to improve sweet corn heterotic groups. A diallel among three sweet corn cultivars (`Country Gentleman', `Golden Bantam', and `Stowell's Evergreen') that are representative of the variability among modern sweet corn cultivars, and three field corn synthetic cultivars [`EPS6(S)C3', `EPS7(S)C3', and `EPS10'] representing the heterotic patterns involving Spanish field corn, was evaluated for 2 years at two locations in northwestern Spain. Differences in heterosis effects (h jj') and average heterosis (h) were significant for all traits except grain moisture. Differences for cultivar heterosis (h j) and specific heterosis (s jj') were significant for grain yield, plant height, and kernel row number. `EPS6(S)C3' had lower s jj' for yield in crosses to `Golden Bantam' than to `Stowell's Evergreen', while `EPS7(S)C3' had higher s jj' in crosses to `Golden Bantam' than to `Stowell's Evergreen'. The best crosses to establish enhanced sweet corn heterotic patterns involving Spanish maize would be `Golden Bantam' × `EPS6(S)C3' and `Stowell's Evergreen' × `EPS7(S)C3'. New sugary 1 cultivars would require preliminary cycles of intrapopulational recurrent selection for agronomic performance and flavor prior initiating an interpopulational recurrent selection program to enhance heterosis.
Increasing demand on agricultural water resources have caused a greater need for the use of municipal recycled wastewater (MRW) globally. However, in the United States, greenhouse growers have been slow to use it in their greenhouse operations. In this study, we seek to understand the factors that motivate and limit use of MRW among US growers. Using national survey data from 2019 through 2020, we developed a logistic regression model to understand the many factors influencing growers’ willingness to use MRW on food crops. We find that MRW quality is a primary concern and that growers’ willingness to use MRW is shaped by their direct and indirect knowledge of MRW, garnered from their own and others’ experiences using it. Given these findings, improving adoption of MRW requires collective experiential learning opportunities that gather target audiences with educators, policymakers, end users, and local authorities to simultaneously provide hands-on experience tailored to growers’ particular knowledge and concerns with feedback from peers.
Consumption of staminate (male) flowers of squash and pumpkin (Cucurbita sp.) has generally been limited to summer squash (Cucurbita pepo), a species of temperate regions or highland tropical environments. In the lowland tropics of the Caribbean Basin, tropical pumpkin (Cucurbita moschata) is better adapted and more widely grown. We evaluated flower production in Lajas, Puerto Rico, and postharvest attributes (shelf life, chemical and nutritional properties, sensory quality) of flowers of four tropical pumpkin and two summer squash cultivars. Tested cultivars varied slightly among experiments. Passive and active modified atmosphere packaging (MAP) were compared. For passive MAP, packages were sealed without further intervention. Under active MAP, packages were adjusted to 6% to 7% oxygen (O2) and 12% to 13% carbon dioxide (CO2) during sealing. Sensory quality of fresh and canned tropical pumpkin flowers was evaluated by panelists. Production ranged from 1.8 to 4.0 flowers/plant per day. Flower weight and length were up to 50% greater in tropical pumpkin compared with summer squash. Packaged flowers turned more orange but with less color saturation as they aged. In active MAP packages, decreases in O2, and increases in CO2 observed after 5 days were small or not significant compared with initially established atmospheres at day 0. Storage temperature generally had no effect on changes in O2 and CO2. Packaged flowers lost about 27% of their initial weight after 5 days. Type of MAP had no consistent effect on the appearance of packaged flowers. Storing flowers at 5 °C often improved appearance compared with storage at 10 °C. The rate of deterioration was slower in packaged flowers of tropical pumpkin compared with summer squash, but by day 6 the poor appearance of flowers of all cultivars made them unmarketable. Compared with fresh flowers, packaged flowers stored for 5 days exhibited a decrease in soluble solids, total acidity, ascorbic acid, antioxidant capacity, and total phenolics, and generally an increase in pH. Beta-carotene often increased in stored flowers although this varied by cultivar. Storage temperature and type of MAP had inconsistent effects on chemical attributes of stored flowers. Panelists rated fresh flowers as “like moderately” to “like very much” for texture, taste, and overall acceptability, whereas canned flowers were rated as “like moderately” for overall acceptability. Male flowers of tropical pumpkin are suitable for human consumption but deterioration after 5 days of storage limits their market potential unless better packaging methods are developed. Canned tropical pumpkin flowers may be an alternative to packaged flowers.
High soil salinity often results in poor stand establishment, reduced plant growth, and reduced yield of many horticultural crops such as peppers (Capsicum annuum). We investigated the effects of soil salinity and soil type on seedling emergence and growth of four commercial peppers (‘NuMex Joe E. Parker’, ‘NuMex Nematador’, ‘NuMex Primavera’, and ‘Jupiter’) in greenhouse experiments. Seeds were sown in either a loamy sand or a silt loam soil in pots and irrigated with saline solutions at electrical conductivity of 0.9 (tap water), 3.0, or 6.0 dS·m−1 (Expt. 1) or at 0.0 [reverse osmosis (RO) water], 0.9, or 1.5 dS·m−1 (Expt. 2). No seedling emergence was observed in treatments irrigated with 3.0 or 6.0 dS·m−1 solutions. The salinity at the top soil layer increased linearly with time when subirrigated with tap and saline solutions in both soil types, whereas no substantial increase in soil salinity was found when subirrigated with RO water or overhead irrigation with tap water. Salt accumulation at the top soil layer was greater in loamy sand than in silt loam. Seedling emergence percent subirrigated with RO water ranged from 70% to 80% in loamy sand and 45% to 70% in silt loam, depending on pepper cultivars. When subirrigated with tap water and saline solutions, the emergence percent ranged from 0% to 60%, depending on pepper and soil types. In Expt. 3, seedlings were germinated in commercial potting mix and grown in 1.8-L pots containing commercial potting mix. Saline solution treatments of 1.4 (control, nutrient solution), 2.1, 2.9, 3.5, or 4.2 dS·m−1 were initiated when seedlings had 11 to 13 leaves. Five weeks after initiating saline water irrigation, the reduction in shoot dry weight was greater in ‘Jupiter’ and ‘NuMex Primavera’ as compared with ‘NuMex Joe E. Parker’ and ‘NuMex Nematador’, but the differences were small.