Tillering is an important biomass yield component trait in switchgrass (
.).
(
)/
(
) gene is a known regulator for tillering/branching in several plant species; however, its role on tillering in ...switchgrass remains unknown. Here, we report physiological and molecular characterization of mutants created by CRISPR/Cas9. We successfully obtained nonchimeric
and
mutants from chimeric T0 mutants using nodal culture. The biallelic
mutant plants produced significantly more tillers and higher fresh weight biomass than the wild-type plants. The increased tiller number in the mutant plants resulted primarily from hastened outgrowth of lower axillary buds. Increased tillers were also observed in transgene-free BC1 monoallelic mutants for either
or
gene alone, suggesting
genes act in a dosage-dependent manner. Transcriptome analysis showed 831 genes were differentially expressed in the
a-
double knockdown mutant. Gene Ontology analysis revealed downregulation of
genes affected multiple biological processes, including transcription, flower development, cell differentiation, and stress/defense responses in edited plants. This study demonstrates that
genes play a pivotal role in tiller production as a negative regulator in switchgrass and provides opportunities for further research aiming to elucidate the molecular pathway regulating tillering in switchgrass.
Controlled environment (CE) food crop production has existed in the United States for many years, but recent improvements in technology and increasing production warranted a closer examination of the ...industry. Therefore, our objectives were to characterize historical trends in CE production, understand the current state of the U.S. hydroponics industry, and use historical and current trends to inform future perspectives. In the 1800s, CE food production emerged and increased in popularity until 1929. After 1929, when adjusted for inflation (AFI), CE food production stagnated and decreased until 1988. From 1988 to 2014, the wholesale value of CE food production increased from $64.2 million to $796.7 million AFI. With the recent increase in demand for locally grown food spurring an increase in CE production, both growers and researchers have been interested in using hydroponic CE technologies to improve production and quality. Therefore, we surveyed U.S. hydroponic food crop producers to identify current hydroponic production technology adoption and potential areas for research needs. Producers cited a wide range of technology utilization; more than half employed solely hydroponic production techniques, 56% monitored light intensity, and more than 80% monitored air temperature and nutrient solution pH and electrical conductivity. Additionally, the growing environments varied from greenhouses (64%), indoors in multilayer (31%) or single-layer (7%) facilities, to hoop houses or high tunnels (29%). Overall, producers reported managing the growing environment to improve crop flavor and the development of production strategies as the most beneficial research areas, with 90% stating their customers would pay more for crops with increased flavor. Lastly, taking historical data and current practices into account, perspectives on future hydroponic CE production are discussed. These include the importance of research on multiple environmental parameters instead of single parameters in isolation and the emphasis on not only increasing productivity but improving crop quality including flavor, sensory attributes, and postharvest longevity.
Broad-spectrum high-pressure sodium (HPS) lamps are the standard for greenhouse supplemental lighting. However, narrow-spectra light-emitting diodes (LEDs) offer potential benefits for enhancing ...growth, photosynthesis (
P
n
), and secondary metabolites in culinary herbs. Our objective was to quantify the effect of supplemental light source and spectra on growth, gas exchange, aroma, and flavor of culinary herbs. Basil (
Ocimum basilicum
‘Nufar’), dill (
Anethum graveolens
‘Fernleaf’), and parsley (
Petroselinum crispum
‘Giant of Italy’) were transplanted into hydroponic systems in a glass-glazed greenhouse. Plants were provided with a supplemental photosynthetic photon flux (
PPF
) density of 100 μmol·m
−2
·s
–1
from an HPS lamp or LEDs with a low blue (B) to red (R) light ratio of 7:93 low blue (LB) or high B:R at 30:70 high blue (HB). Compared with plants grown under HPS lamps, basil grown under LB and HB LED lighting was shorter, while only HB-grown parsley was shorter; height of dill was unaffected by light source. Basil and parsley shoot fresh weight was lower for HB-treated plants compared with HPS, though dill was unaffected by supplemental light source. Shoot dry mass of basil, dill, and parsley was unaffected by light source. Both LED treatments increased
P
n
for basil and parsley compared with HPS-grown plants. Stomatal conductance (
g
S
) was higher under LB and HB for basil compared with HPS in the morning and evening, but only HB-treated parsley was higher than HPS lighting in morning. Basil grown under LB, and parsley under both LEDs had lower chlorophyll fluorescence than those under HPS by the evening, but all three species had more chlorophyll b under LB light than HPS. Essential oil and phenolic accumulation were influenced by supplemental light treatment and responses varied among species. Lighting from LEDs resulted in a 2-fold increase in orientin and myristicin for basil and dill, respectively, while HB increased dillapiole concentration by 89% compared with HPS-grown dill. Notably, quercetin concentration was 2.8 times higher in dill grown under HB compared with HPS. Myrcene increased in all three species under either one (basil HB; dill LB) or both (parsley) LED lights compared with HPS. The increased content of aromatic and flavor compounds demonstrates the potential of supplemental lighting systems using specific wavelengths to add value; but the use of supplemental lighting requires an understanding of the additional stress on the photosynthetic mechanisms and the subsequent effect on biomass accumulation.
Few microbial studies in aquaponics, a growing trend in food production, have been conducted to determine food safety status. The aim of this study was to determine the food safety status and the ...effectiveness of ultraviolet treatment (15 W, luminous flux of 900 lm) as a food safety intervention in reducing the microbial loads of the water system in a model aquaponic unit growing lettuce, basil, and barramundi (Australian Sea Bass). Sweet basil, bibb lettuce, water samples, and fish swabs were collected throughout the 118-day production period, and microbial analysis was conducted in triplicate for the presence of E. coli O157:H7, Salmonella spp., and the prevalence of aerobic plate counts (APC), coliforms, and fecal coliforms in these systems. Absence of foodborne pathogens was confirmed using ELISA technology and enumeration through petrifilms (coliform/E. coli). A significant increase was observed in aerobic plate counts over the trial period (1 to 3 logsub.10 CFU·mLsup.−1) in the presence and absence of UV (p > 0.05). Ultraviolet treatment did not significantly reduce the APC or coliform counts when compared to the control system samples. Future work should focus on improving the unit design, the evaluation of bio-solid filtration, and other food safety interventions.
The objective of this research was to quantify the effects of phosphorous (P) concentrations on the growth, development, and tissue mineral nutrient concentrations of four popular culinary herbs ...commonly grown in containers. Seedlings of sweet basil ( Ocimum basilicum ‘Italian Large Leaf’), dill ( Anethum graveolens ‘Fernleaf’), parsley ( Petroselinum crispum ‘Giant of Italy’), and sage ( Salvia officinalis ) were individually transplanted to 11.4-cm-diameter containers filled with soilless substrate comprising canadian sphagnum peatmoss and coarse perlite. Upon transplanting and throughout the experiment, seedlings were irrigated with solutions containing 0, 5, 10, 20, or 40 mg·L −1 P; all other macro- and micronutrient concentrations were the same across P concentrations. Plants were grown for 4 weeks in a greenhouse; after that time, data were collected. Relationships between height and width and P concentrations were nonlinear for all four species; height and width increased as P increased to more than 0 mg·L −1 until the species-specific maxima; after that time, no further increase occurred. The same trend was observed for the branch length of sweet basil and sage, and for internode length, leaf area, and shoot dry mass of all four species. Although visible P deficiency symptoms were observed for plants provided with 0 mg·L −1 P, there were no signs of P deficiency for plants provided with ≥5 mg·L −1 P, even though tissue P concentrations were below the recommended sufficiency ranges. As a result of this research, containerized sweet basil, dill, parsley, and sage can be provided with 5 to 10 mg·L −1 P during production to limit growth and produce plants without visible nutrient deficiency symptoms that are proportional to their containers.
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