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Open access

Andrew Sherwood, Lisa W. Alexander, Matthew D. Clark, Xingbo Wu, and Stan C. Hokanson

Oakleaf hydrangea (Hydrangea quercifolia) is an understory shrub native to the southeastern United States. The species occupies a relatively small native range, and little is known about its demography, genetic diversity, or needs for conservation. Samples were collected from 188 plants in 73 locations throughout the species range and were genotyped using genotyping by sequencing. A structure analysis identified six genetic clusters that are geographically defined. Although these clusters are weakly differentiated, each has unique alleles. An environmental association analysis revealed that environmental variables explain 11.3% of genetic diversity, and population structure explains 13.5%. Further, 231 putative adaptive alleles were identified, most of which are correlated with precipitation-related variables, indicating that precipitation has an impact on genetic diversity in H. quercifolia. Many historically documented populations were found to be either extirpated or at risk of extirpation. The genetic clusters on the southern extent of the species range are relatively small and contain putative adaptive alleles at relatively high frequencies. These results highlight the importance of preserving representative germplasm from throughout the species range.

Open access

Serge Lévesque, Thomas Graham, Dorin Bejan, Jamie Lawson, and Mike Dixon

Recirculating nutrient solutions were treated using dimensionally stable anode (DSA)-based regenerative in situ electrochemical hypochlorination (RisEHc) in a deep water culture hydroponic lettuce (Lactuca sativa) production system. Phytotoxic effects were noted and attributed to the formation of chloramines in treated nutrient solutions containing ammonium. The presence of chloramines resulted in a decrease in overhead biomass by 53% using 2.27 mA/cm2 and 83% with 4.55 mA/cm2. Adding ultraviolet light as a tertiary treatment stage allowed the photodecomposition of chloramines, which prevented phytotoxicity in crops and caused no significant differences in growth between treatments. Furthermore, using a nitrate-based fertilizer also served to prevent phytotoxic effects in crops and showed no significant differences in growth between the control and 4.55 mA/cm2. In addition, it was found that the electrochemical flow cell (EFC) treatment resulted in a 13% increase in shoot biomass using 2.27 mA/cm2. The study demonstrated that phytotoxic effects can be prevented with the use of regenerative in situ hypochlorination through proper management and monitoring techniques in recirculating hydroponic systems.

Open access

Paul C. Bartley III, Ted C. Yap, Brian E. Jackson, William C. Fonteno, Michael D. Boyette, and Bernardo Chaves-Cordoba

The ability of a substrate component (organic or inorganic) to capture and retain water (hydration and wettability) is important to investigate and promote water-use–efficient practices. Many factors may play a role in the wettability of the material, including the processing of the material and its initial handling. The goal of this experiment was to determine the effect of moisture content (MC) on the sorptive behavior of substrates after an initial and secondary hydration cycle. Coir, peat, and aged pine bark were evaluated at a 33%, 50%, and 66% MC by weight. At all moisture levels, coir and bark were minimally affected by MC or the initial hydration cycle. Peat was the most vulnerable to changes in sorptive behavior as a result of wetting and drying cycles. After a wetting and drying cycle, the maximum volumetric water content of peat from surface irrigation was reduced 21.5% (volumetrically), more than three times any other treatment. The hydration efficiency of peat was improved when blended with as little as 15% coir. These experiments provide evidence that MC and initial handling of the substrate can lead to differences in initial water use efficiency.

Open access

Masoomeh Hosseini Nickravesh, Kourosh Vahdati, Fatemeh Amini, Erica A. Di Pierro, Reza Amiri, Keith Woeste, and Mohammad M. Arab

Simple sequence repeat (SSR) markers were used to authenticate ramets of 11 Persian walnut (Juglans regia L.) varieties. All varieties and 28 of their ramets (n = 39) were genotyped with 17 SSR markers. The genetic profiles revealed two off-types: the ramets Serr 4 (S4) and Vina 1 (V1). SSR fingerprints individuating 11 walnut varieties were possible using 13 polymorphic SSRs that could be used in the future to identify clones of these varieties. Except for ‘Chandler’, each cultivar could be distinguished using a combination of two SSR loci. This result emphasizes the efficacy of the SSR markers in true-to-type validation of walnut orchards.

Open access

Junjie Peng, Jingjia Du, Tiantian Chen, Xian Shui, Haizhi Liao, Xiaokai Lin, and Kaibing Zhou

Ten 16-year-old trees were used as test materials to investigate the effect of foliar calcium fertilizer on the sugar content of ‘Feizixiao’ litchi (Litchi chinensis Sonn.) pulp. The experiment began 35 days after anthesis (DAA) in 2020 and 2021, and the treatment was a foliar spray application of 0.3% CaCl2 aqueous solution, whereas the control was a foliar spray application of water. The sugar content, sucrose-metabolizing enzymes, and ATP-dependent phosphofructokinase (PFK) activities in pulp were measured in 2020 and 2021. Transcriptome sequencing (RNA-seq) was performed on RNA samples from treatment and control fruit pulps at 35, 63, and 69 DAA (full mature stage) in 2020, and 10 genes were chosen for confirmation by real-time polymerase chain reaction (PCR) in 2020 and 2021. At full maturity, the soluble sugar content in the calcium-treated group was extremely significantly or significantly higher than that in the control group. After 63 DAA, the net sucrose-metabolizing enzyme activity in the calcium-treated group was significantly higher than that in the control group. Furthermore, at full maturity, the calcium-treated group had significantly higher sucrose synthase cleavage activity and significantly lower PFK activity than the control group. Fifty-four highly expressed genes in the glycolytic pathway (EMP) were screened from transcriptome data, including hexokinase, PFK, and pyruvate kinase genes; 87% of these genes were downregulated in the treatment group compared with the control group at 69 DAA in 2020. The linear regression between RNA-seq and real-time PCR results was significant in 2020 (r = 0.9292) and 2021 (r = 0.8889). When the fruit is fully ripe, calcium treatment increases net sucrose-metabolizing enzyme activity by increasing sucrose synthase cleavage activity, promoting the accumulation of reducing sugars, and it downregulates phosphofructokinase gene expression in EMP, promoting sugar accumulation.

Open access

Dan Wang, Ying Ma, Xueli Zhao, Guiling Liu, Ling Wang, and Fude Wang

Open access

Xi Wang, Huihui Xu, Xiaojuan Liu, Yingchao Li, Haiyan Yu, Quanxin Bi, and Libing Wang

Open access

Asmita Nagila, Soum Sanogo, O. John Idowu, and Brian J. Schutte

Soil-borne diseases and weeds can be inhibited by mustard family (Brassicaceae) cover crops that are mowed and incorporated into the soil with tillage—a process referred to as biofumigation. To determine whether a fall-seeded mustard cover crop produces enough biomass to be a biofumigant in spring, this study measured the amount of biomass produced by a mixture of ‘Caliente Rojo’ brown mustard (Brassica juncea) and ‘Nemat’ arugula (Eruca sativa) grown in three commercial fields and a university research farm in southern New Mexico, USA. This study also determined whether the mustard biomass incorporated in the soil inhibits a weed [Palmer amaranth (Amaranthus palmeri)], but does not affect a cash crop adversely [chile pepper (Capsicum annuum)]. Results indicated that, if the mustard cover crop was seeded before the first frost in fall, mustard cover crops produced biomass in quantities sufficient for biofumigation in spring. Mustard biomass incorporated in the soil reduced the survival and germination of Palmer amaranth seeds. Under greenhouse conditions, chile pepper plants grown in soil with mustard cover crop biomass were larger than chile plants grown in soil without mustard biomass. Chile pepper plants in soil with mustard biomass did not show symptoms of Verticillium wilt (Verticillium dahliae), whereas such symptoms were found on about 33% of chile pepper plants in soil without mustard biomass. These results suggest that a fall-seeded mustard cover crop that is tilled into the soil in early spring is a potential pest management technique for chile pepper in New Mexico.

Open access

Brandon Miller and Nina Bassuk

Impressive ornamental features including exfoliating bark and golden fall color are among the reasons why hickories [Carya (Nutt.)] are sought after by horticulturists. Their potential for application in the green industry continues to grow as producers and consumers in the United States become more interested in adopting native plants; however, an absence of knowledge that defines which species are tolerant of abiotic stresses in the landscape limits their use. If production of stress-tolerant hickories increases, they could be used to diversify urban forests and may bolster the resiliency of managed landscapes. We examined the predicted leaf water potential at the turgor loss point to estimate drought tolerance among several species of hickories and pecans adapted to growing in northern climates in the United States. Our hypotheses were that because some bottomland habitats experience seasonal drought in addition to flooding, taxa adapted to these sites may be more drought tolerant than previously assumed, and that the degree of drought tolerance would be variable within species and populations. Predicted mean leaf turgor loss measured in summer across species was −3.38 MPa. Kingnut hickory [Carya laciniosa (F. Michx.) Loud.] exhibited the lowest mean summer leaf turgor loss point −3.64 MPa), whereas pignut hickory [Carya glabra (Mill.) Sweet.] exhibited the highest (−3.20 MPa). Provenance of trees studied influenced estimated drought tolerance of C. laciniosa. Variability between individual trees within each species was observed, suggesting clonal selections of each taxon can be made for drought-prone landscapes. The results of this work imply that all the species studied are at least moderately drought tolerant and should be considered for planting in managed landscapes. Further, species often associated with riparian habitats may exhibit substantial tolerance to drought and should not be excluded from use on drought-prone sites.