The relationship between soil texture and the degree of apple replant disease (ARD) was analyzed from the perspective of the microbial community structure and diversity within the rhizosphere soil of Malus hupehensis Rehd. seedlings. Three different textured soils were taken from different apple orchards in Laizhou, Yantai. The soils were divided into two parts, one was kept in replanted conditions, and the other was fumigated with methyl bromide to act as a high standard control. The strength of ARD occurrence was examined by measuring fresh and dry weight suppression (%) of the M. hupehensis seedlings. Differences in the fungal community structure (especially in Fusarium) among the three soil texture types were analyzed using high-throughput sequencing. The results showed that replanted loam clay soil had the highest fungal diversity, followed by sandy loam soil and finally loam soil. The richness of fungi between soil textures, however, was not significantly different. At the genus level, the relative abundance of Fusarium was 1.96%, 0.78%, and 10.89% in replanted sandy loam, replanted loam soil, and replanted loam clay soil, respectively. Moreover, the gene copy number of Fusarium oxysporum, Fusarium solani, and the inhibition rate of fresh weight of M. hupehensis seedlings were the same in the three soil textures. The plant height, photosynthesis (net) (Pn), and stomatal conductance (g S) of the M. hupehensis seedlings were significantly less in the replanted soil compared with the control treatments, with the overall difference being greatest in replanted loam clay soil, followed by replanted sandy loam and then replanted loam soil.
Haiyan Wang, Ran Chen, Yuefan Sheng, Weitao Jiang, Rong Zhang, Xuesen Chen, Xiang Shen, Chengmiao Yin, and Zhiquan Mao
Haiyan Wang, Rong Zhang, Weitao Jiang, Yunfei Mao, Xuesen Chen, Xiang Shen, Chengmiao Yin, and Zhiquan Mao
The study here aimed to investigate the effects of pre-winter ditching and freezing-thawing on soil microbial structure in different soil layers of old apple orchards. A total of 30 samples were obtained from 3 Nov. 2016 to 9 Mar. 2017. The relative abundance, alpha diversity, community structure of fungi, and the relationship between environmental factors and microbial community structure were analyzed, and the greenhouse experiments were used for further verification. Results showed that the number of actinomycete and total bacterial colonies decreased, whereas the number of fungi sustained decreased, resulting in a higher bacteria/fungi ratio. The percentage of Fusarium initially decreased, then later increased by 11.38%, 3.469%, 2.35%, 2.29%, and 3.09%. However, Fusarium levels were still 9% lower on 9 Mar. 2017 that on 3 Nov. 2016. Both the abundance and diversity of the community were higher in the upper soil than in the lower. The main environmental factor contributing to the percentage of Fusarium change was average temperature (AT), although highest temperature (HT) and water content (WC) also had an impact. The Malus hupehensis Rehd. seedlings growing in lower soil were more vigorous than that in upper soil. In sum, pre-winter ditching and freezing-thawing in old apple orchards can reduce the abundance percentage of harmful Fusarium and promote the growth of M. hupehensis Rehd. seedlings.
Qiang Liu, Youping Sun, Genhua Niu, James Altland, Lifei Chen, and Lijuan Jiang
Because of limited supply of high-quality water, alternative water sources have been used for irrigation in water-scarce regions. However, alternative waters usually contain high salt levels, which can cause salt damage on salt-sensitive plants. A greenhouse study was conducted to evaluate the relative salt tolerance of 10 common ornamental taxa to saline water irrigation. The 10 taxa studied were Chaenomeles speciosa ‘Orange Storm’ and ‘Pink Storm’ (Chaenomeles Double Take™); Diervilla rivularis ‘G2X885411’, ‘G2X88544’ (Diervilla Kodiak®, Black, Orange, and Red, respectively), and ‘Smndrsf’; Forsythia ×intermedia ‘Mindor’ (Forsythia Show Off®); Hibiscus syriacus ‘ILVOPS’ (Hibiscus Purple Satin®); Hydrangea macrophylla ‘Smhmtau’ and ‘Smnhmsigma’ (Hydrangea Let’s Dance® Blue Jangles® and Rave, respectively); and Parthenocissus quinquefolia ‘Troki’ (Parthenociss quinquefolia Red Wall®). Plants were irrigated with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solutions at EC of 5.0 or 10.0 dS·m−1 (EC 5 or EC 10) eight times on a weekly basis. The results indicated that the 10 ornamental taxa had different morphological and physiological responses to salinity. The C. speciosa and D. rivularis plants in EC 5 had severe salt foliar damage, whereas those in EC 10 were dead. Hibiscus syriacus ‘ILVOPS’ performed well in EC 5 treatment with a shoot dry weight (DW) reduction of 26%, but those in EC 10 had severe foliar salt damage. Hydrangea macrophylla, F. ×intermedia ‘Mindor’ and P. quinquefolia ‘Troki’ were the most salt tolerant with minor foliar salt damage. The two H. macrophylla cultivars had the highest shoot sodium (Na) and chlorine (Cl) concentrations with a visual quality of 3 (scale 0 to 5 with 0 for dead plants and 5 for excellent performance), indicating that H. macrophylla plants adapted to elevated salinity by tolerating high Na and Cl concentrations in leaf tissue. Forsythia ×intermedia ‘Mindor’ and P. quinquefolia ‘Troki’ had relatively low leaf Na and Cl concentration, indicating that both taxa are capable of excluding Na and Cl. Chaenomeles speciosa and D. rivularis were sensitive to salinity with great growth reduction, severe foliar salt damage, and high Na and Cl accumulation in leaf tissue.
Junqin Zong, Yanzhi Gao, Jingbo Chen, Hailin Guo, Yi Wang, Fan Meng, Yiwei Jiang, and Jianxiu Liu
Waterlogging (WL) negatively affects plant growth and development, but the physiological responses of turfgrass species to WL are not well understood. The objective of this study was to examine growth and physiological mechanisms of WL tolerance in warm-season turfgrass species. Knotgrass (Paspalum paspaloides), spiny mudgrass (Pseudoraphis spinescens), seashore paspalum (Paspalum vaginatum), and centipedegrass (Eremochloa ophiuroides) were subjected to 30 days of WL. At the end of the treatment, knotgrass and spiny mudgrass maintained the shoot and root biomass while seashore paspalum and centipedegrass showed reductions in biomass under WL. Root oxidase activity (ROA) was unaffected until after 12 or 18 days of WL but decreased by 14.3%, 17.8%, 32.0%, and 68.7% at 30 days of WL for knotgrass, spiny mudgrass, seashore paspalum, and centipedegrass, respectively. Waterlogging increased root activities of lactate dehydrogenase and alcohol dehydrogenase, but generally to a lesser extent in knotgrass and spiny mudgrass. The leaf and root activities of superoxide dismutase (SOD) and peroxidase (POD) were induced after 6 or 12 days of WL, but to a greater extent for knotgrass and spiny mudgrass. At 30 days of WL, the increased leaf and root activities of SOD and POD were higher in knotgrass and spiny mudgrass than that of seashore paspalum and centipedegrass; while centipedegrass showed 37.8% reduction in root SOD activity. The total soluble protein (TSP) concentration remained unchanged in both leaves and roots during the entire WL treatment for knotgrass, while a decreased leaf TSP was found in the other three species after 12 or 24 days of WL as well as in the roots of seashore paspalum and centipedegrass. More reductions in leaf or root TSP were observed in seashore paspalum and centipedegrass than in knotgrass and spiny mudgrass at 30 days of WL. The results indicated that higher ROA, activities of antioxidant enzymes and TSP contributed to WL tolerance of warm-season turfgrass species.
Yihua Chen, Peng Jiang, Shivegowda Thammannagowda, Haiying Liang, and H. Dayton Wilde
We investigated the FT/TFL1 family of peach (Prunus persica), a gene family that regulates floral induction in annual and perennial plants. The peach terminal flower 1 gene (PpTFL1) was expressed in a developmental and tissue-specific pattern that, overall, was similar to that of TFL1 orthologs in other woody Rosaceae species. Consistent with a role as a floral inhibitor, ectopic expression of PpTFL1 in arabidopsis (Arabidopsis thaliana) delayed flowering and prolonged vegetative growth. Other members of the peach FT/TFL1 family were identified from the sequenced genome, including orthologs of flowering locus T, centroradialis, brother of ft, and mother of ft and tfl. Sequence analysis found that peach FT/TFL1 family members were more similar to orthologous genes across the Rosaceae than to each other. Together these results suggest that information on genes that regulate flowering in peach could be applied to other Rosaceae species, particularly ornamentals.
Chen Jiang, Penelope Perkins-Veazie, Sylvia M. Blankenship, Michael D. Boyette, Zvezdana Pesic-VanEsbroeck, Katherine M. Jennings, and Jonathan R. Schultheis
A series of studies were conducted to better understand the occurrence and causes of internal necrosis (IN) in ‘Covington’ sweetpotato (Ipomoea batatas). Assessment of the problem among the industry was done for 2 years and revealed that IN was widespread in commercial storage facilities throughout the state of North Carolina; both incidence and severity were generally low (<10% incidence with minimal severity of symptoms). A few storage rooms had a high percentage of IN with severe storage root symptoms but results were inconsistent across years and among rooms. Preharvest studies with commercially used insecticides did not induce IN, but the harvest aid ethephon consistently induced IN with an incidence higher than 50%. Internal necrosis symptoms were not detectable at harvest, and earliest consistent incidence was observed 6 days after harvest (DAH) during the curing phase. Symptoms became more prevalent and severe at 30 DAH. However, in commercial storage rooms, no relationship was found between IN incidence and postcuring storage temperature or relative humidity (RH) conditions. Sweetpotato storage roots stored in air-tight barrels and exposed to 100 ppm ethylene after curing showed no relationship between the presence of ethylene gas in storage and incidence of IN. Our results indicate that IN incidence of ‘Covington’ is erratic with no obvious cause among storage rooms and that initiation of IN may occur most frequently during the first week following harvest.
Peter J. Dittmar, Jonathan R. Schultheis, Katherine M. Jennings, David W. Monks, Sushila Chaudhari, Stephen Meyers, and Chen Jiang
The reason for internal necrosis occurrences in sweetpotato (Ipomoea batatas) storage roots is not well understood. This disorder begins internally in the storage roots as small light brown spots near the proximal end of the root that eventually can become more enlarged as brown/black regions in the cortex. The objective of this study was to determine the effect of ethephon and flooding on the development of internal necrosis in the sweetpotato cultivars Beauregard, Carolina Ruby, and Covington over storage durations from 9 to 150 days after harvest (DAH) when roots had been cured. Soil moisture treatments were no-flooding, and simulated flooding that was created by applying 10 inches of overhead irrigation during 2 weeks before harvest. Ethephon was applied at 0, 0.75, and 0.98 lb/acre 2 weeks before harvest. Overall, ‘Covington’ and ‘Carolina Ruby’ had greater internal necrosis incidence (22% to 65% and 32% to 51%, respectively) followed by ‘Beauregard’ (9% to 22%) during storage duration from 9 to 150 DAH at both soil moistures. No significant change was observed for either internal necrosis incidence or severity for ‘Beauregard’ and ‘Carolina Ruby’ over the storage duration of 9–150 DAH. However, there was an increase of internal necrosis incidence and severity 9–30 DAH in ‘Covington’, with incidence and severity remaining similar 30–150 DAH. Storage roots in treatments sprayed with 0.75 or 0.98 lb/acre ethephon had higher internal necrosis incidence and severity compared with the nontreated, regardless of cultivars at both soil moistures. This research confirms that sweetpotato cultivars differ in their susceptibility to internal necrosis (incidence and severity), ethephon applied to foliage can contribute to internal necrosis development in storage roots, and internal necrosis incidence reaches a maximum by 30 DAH in ‘Covington’ and 9 DAH in ‘Carolina Ruby’ and ‘Beauregard’.
Ahmad Hassan, Chen Qibing, Jiang Tao, Lv Bing-Yang, Li Nian, Shu Li, Li Yu Tng, Jun Zhuo Li, Shang Guan Ziyue, and Muhammad Sohaib Tahir
Advancements in electronic devices have led to increases in mental stress in modern adults, and removing this stress is crucial for mental health. The purpose of this study is to examine the psychophysiological benefits of contact with indoor plants. The effects of transplanting plants (horticultural activity) and work on a mobile phone (control activity) were assessed by blood pressure measurement, electroencephalography (EEG), the semantic differential method (SDM), and the State-Trait Anxiety Inventory (STAI). The SDM data showed that the subjects felt more relaxed, comfortable and natural, and experienced lower anxiety after the transplantation of plants than the control group. Participant’s total alpha and beta wave mean values increased over time during the transplantation task but decreased at the end of the control task. The mean meditation score was significantly higher after transplanting plants. Our study results indicate that contact with plants may minimize mental stress.
Christopher A. Clark, Washington L. da Silva, Ramón A. Arancibia, Jeff L. Main, Jonathan R. Schultheis, Zvezdana Pesic van-Esbroeck, Chen Jiang, and Joy Smith
Two distinct syndromes have emerged in some production areas that have caused losses of sweetpotato (Ipomoea batatas) storage roots during postharvest storage: a complex of fungal rots (end rots) progressing from either end of storage roots and a necrotic reaction (internal necrosis) progressing internally from the proximal end of storage roots. This study was conducted in multiple environments to evaluate whether the use of preharvest ethephon application and storage with or without curing after harvest could be used to screen sweetpotato breeding lines for susceptibility/resistance to these two disorders. Treating vines with ethephon 2 weeks before harvest and placing harvested roots directly into storage at 60 °F without curing resulted in the greatest incidence of end rots in each state and there were significant differences in incidence among the sweetpotato genotypes evaluated. However, when ethephon was not used and roots were cured immediately after harvest, the incidence of end rots was low in all the genotypes evaluated except for one breeding line. Incidence and severity of internal necrosis were greatest when ethephon was applied preharvest and roots were cured immediately after harvest, but two cultivars, Hatteras and Covington, had significantly more internal necrosis than all others.
Tingting Zhao, Jingkang Hu, Yingmei Gao, Ziyu Wang, Yufang Bao, Xiaochun Zhang, Huanhuan Yang, Dongye Zhang, Jingbin Jiang, He Zhang, Jingfu Li, Qingshan Chen, and Xiangyang Xu
Zinc finger-homeodomains (ZF-HDs) are considered transcription factors that are involved in a variety of life activities in plants, but their function in regulating plant salt stress tolerance is unclear. The SL-ZH13 gene is significantly upregulated under salt stress treatment in tomato (Solanum lycopersicum) leaves, per our previous study. In this study, to further understand the role that the SL-ZH13 gene played in the response process of tomato plants under salt stress, the virus-induced gene silencing (VIGS) method was applied to down-regulate SL-ZH13 expression in tomato plants, and these plants were treated with salt stress to analyze the changes in salt tolerance. The silencing efficiency of SL-ZH13 was confirmed by quantitative real-time PCR analysis. SL-ZH13-silenced plants wilted faster and sooner than control plants under the same salt stress treatment condition, and the main stem bending angle of SL-ZH13-silenced plants was smaller than that of control plants. Physiological analysis showed that the activities of superoxide dismutase, peroxidase, and proline content in SL-ZH13-silenced plants were lower than those in control plants at 1.5 and 3 hours after salt stress treatment. The malondialdehyde content of SL-ZH13-silenced plants was higher than that in control plants at 1.5 and 3 hours after salt stress treatment; H2O2 and O2 - accumulated much more in leaves of SL-ZH13-silenced plants than in leaves of control plants. These results suggested that silencing of the SL-ZH13 gene affected the response of tomato plants to salt stress and decreased the salt stress tolerance of tomato plants.