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Stunted vegetative growth and delayed or absent flowering are commonly observed in eustoma (Eustoma grandiflorum) when cultivated continuously in the same greenhouse soil. These effects are likely caused by the excessive accumulation of soluble salts and/or phytotoxic organic acids in the soil. This study aimed to clarify the mechanism of continuous cropping obstacles and formulate prevention measures of eustoma. Seedlings of eustoma ‘Croma III White’ were grown hydroponically with 0%, 25%, 50%, 75%, 100% (full), 125%, 150%, 175%, or 200% strength of Johnson’s solution. Plant height, leaf area, and shoot dry weight increased steadily as solution strength increased from 25% to 125% [solution electrical conductivity (EC) of 2.4 dS⋅m−1] and then gradually decreased as solution strength further increased from 125% to 200% (solution EC of 3.8 dS⋅m−1). When grown hydroponically in 200% strength Johnson’s solution, plant height, leaf area, and root length increased with increasing equimolar mixtures of organic acids, including maleic acid, benzoic acid, malic acid, and hydroxybenzoic acid, up to 1.2 to 1.6 mM and decreased thereafter. Node number and the percentage of flower bud visibility declined beyond 1.6 mM organic acid mixtures. Plants with 2.0 and 2.4 mM organic acid mixtures had the lowest net photosynthetic rate, stomatal conductance, transpiration, and intercellular carbon dioxide concentration. Plants had normal growth and produced flower buds when the continuously cropped soil was preconditioned with 100 °C reverse-osmosis water before planting.
To assess the genetic diversity among lotus (Nelumbo) accessions and evaluate the correlation between genetic variation and morphological classification, we sampled 138 accessions: two of N. lutea, 112 of N. nucifera, 17 of hybrids between N. nucifera and N. lutea, and seven Japanese cultivars. The 11 selected combinations of amplified fragment length polymorphism (AFLP) primers produced 138 polymorphic loci, and the percentage of polymorphism was 28.7%. The unweighted pair group method with arithmetic mean (UPGMA) dendrogram clustered all the accessions into two groups: Group I comprised N. lutea and its hybrids with N. nucifera; Group II included N. nucifera and its hybrids with N. lutea and Japanese cultivars. Population structure analysis identified four main clusters: N. lutea clustered mainly in C1, whereas N. nucifera clustered in C2, C3, and C4, which was consistent with the UPGMA and principal coordinate analysis results. The Japanese cultivars were related more closely to N. nucifera (genetic similarity coefficient = 0.74) than to N. lutea (0.46); hence, the Japanese cultivars can be classified as N. nucifera. Moreover, rhizome lotuses formed a separate subclade, whereas seed lotuses were interspersed among flower lotuses, which demonstrated that rhizome lotuses were distinct from flower and seed lotuses. Plant size, flower color, and other morphological criteria used commonly to classify lotuses were correlated with genetic variation to a certain extent but not sufficiently for accurate classification. It appears that it is necessary to use both DNA markers and morphological characteristics to classify lotus species and cultivars.
In Taiwan, the major yield constraint in pineapple cultivation is natural flowering, which occurs when daylengths are shorter and nights are cooler. This natural (precocious) flowering increases the cost of cultivation and reduces the percentage of fruits of marketable size. Two field experiments were conducted to evaluate the inhibitory potential of aviglycine [(S)-trans-2-amino-4-(2 aminoethoxy)-3-butenoic acid hydrochloride, AVG] on natural flowering of ‘Tainon 17’ pineapple plants during the 2003 to 2004 and 2004 to 2005 cropping seasons. In the 2003 to 2004 season, bolting in the control exceeded 80% on 2 Mar. 2004, whereas no bolting was observed in the treatments. Inhibition of bolting by aviglycine (AVG) was dependent on the concentration and frequency of application. Bolting was less than 40% when plants were treated in Nov. and Dec. 2003 with 500 mg·L−1 of AVG four times at 15-day intervals or with five applications made at 10-day intervals. For the 2004 to 2005 season, bolting of plants treated with 250 or 375 mg·L−1 AVG was delayed 4 weeks relative to the control, whereas bolting was delayed 7 weeks by four or five applications of 500 mg·L−1 of AVG applied at 10- or 15-day intervals. Both experiments showed that four to five applications of 500 mg·L−1 of AVG at 10- or 15-day intervals delayed inflorescence emergence relative to the control for the duration of the treatments. We assume control was maintained for 1 to 2 weeks after treatments stopped. Based on these results, the date AVG treatments stop can be used to estimate the duration of delay in flowering. AVG inhibits ethylene biosynthesis and has the potential to be effectively used to delay or completely control the problem of precocious flowering and associated crop losses in pineapple.
Apple replant disease (ARD) causes enormous economic loss and threatens the survival of apple industry worldwide. Fusarium solani is one of the pathogens that has been proven to cause ARD. Samples were collected at different time periods to investigate the mechanism of defense responses of apple to F. solani infection by monitoring the biomass, reactive oxygen species (ROS), and antioxidant enzyme activities of the apple rootstock ‘M.9T337’. In addition, the abundance of transcription of four pathogenesis-related (PR) proteins involved in antifungal defense was monitored. The results showed that the apple root system was normal and had small brown areas. However, there is a rapid burst of ROS during the early infection stage, and the activities of antioxidant enzymes and transcription of PRs increased during this period. With the extension in infection time, the infected root tissues displayed dark brown necrosis, and the activities of antioxidant enzymes and abundance of transcription of PRs decreased gradually after reaching their peak. Eventually, the plant biomass decreased, and the plant died. In conclusion, the levels of ROS and activities of antioxidant enzymes played an active role during the early stage of resistance of ‘M.9T337’ apples to infection by F. solani. Infection by F. solani can destroy the ROS scavenging system, causing oxidative damage and inhibiting the growth of apple rootstocks.
NAC transcription factors have been characterized in numerous plants, and the NAC gene has been shown to be involved not only in plant growth and development, but also in plant responses to abiotic and biological stresses, such as drought, high salinity, low temperature, and anaerobic/hypoxic stress. Creating an environment of anaerobic/hypoxic stress has been shown to be one of the effective storage methods for delaying the browning of fresh-cut lotus (Nelumbo nucifera) root. However, whether NAC is associated with lotus root browning under anaerobic stress has not been studied. In this study, vacuum packaging (VP; anaerobic/hypoxic stress) effectively delayed the browning of fresh-cut lotus root. The changes in the expressions of NnPAL1, NnPPOA, and NnPOD2/3 were consistent with phenylalanine aminolase, polyphenol oxidase (PPO), and peroxidase (POD) enzyme activity changes and lotus root browning. Using RNA sequencing, five NnNAC genes were isolated and studied. Transcriptional analysis indicates that the NnNAC genes showed different responses to VP. The expressions of NnNAC1/4 were inhibited by VP, which was consistent with the observed change in the degree of fresh-cut lotus root browning. However, NnNAC2 messenger RNA (mRNA) levels were upregulated, and the expressions of NnNAC3/5 showed no clear differences under different packaging scenarios. Thus, NnNAC1/4 were identified as promising candidates for further transcriptional regulation analysis in lotus root to understand more fully the molecular mechanism of browning under anaerobic/anoxic stress.
Ethylene response factor (ERF) genes have been involved in responses to biotic and abiotic stress, including hypoxia and anaerobic stress. Vacuum packaging (a typical anaerobic stress) is an effective storage method used to delay browning of fresh-cut lotus root (Nelumbo nucifera). In model plants, ERF genes have been identified as responsive to hypoxia. Whether ERF is associated with browning of vacuum-packaged lotus root has not been studied. The effects of vacuum packaging on browning, phenolic content, the enzyme activity of phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD), and PPO, PAL, POD, and ERF genes expression in fresh-cut lotus root were studied. Downregulation of NnPAL1, NnPPOA, and NnPOD2/3 attributable to vacuum packaging coincided with increased related enzyme activities and the degree of browning of fresh-cut lotus root. The expression patterns of NnERF4/5 were consistent with the changes in NnPAL1, NnPPOA, and NnPOD2/3 gene expression. It has been proposed that NnERF4/5 could have be important regulators of fresh-cut lotus root browning, and that the relationships of NnERF4/5 and NnPAL1, NnPPOA, and NnPOD2/3 should to be studied further.
Ethylene response factor (ERF) genes have been characterized in numerous plants, where they are associated with responses to biotic and abiotic stress. Modified atmosphere packaging (MAP) is an effective treatment to prevent lotus root browning. However, the possible relationship between ERF transcription factors and lotus root browning under MAP remains unexplored. In this study, the effects of phenol, phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD) enzyme activities; and PPO, PAL, POD, and ERF gene expression on fresh-cut lotus root browning were studied with MAP. The expression pattern of ERF2/5 correlated highly with the degree of browning. It is suggested that NnERF2/5 can be used as an important candidate gene for the regulation of fresh-cut lotus root browning under MAP, and the correlation of each gene should be studied further.
Cold stress is one of the most important environmental factors affecting crop growth and agricultural production. Induced changes of gene expression and metabolism are critical for plants responding and acclimating to cold stress. Banana (Musa sp.) is one of the most important food crops in the tropical and subtropical countries of the world. Banana, which originated from tropical regions, is sensitive to cold, which can result in serious losses in commercial banana production. To investigate the response of the banana to cold stress conditions, changes in protein expression were analyzed using a comparative proteomics approach. ‘Brazil’ banana (Musa acuminata AAA group) is a common banana cultivar in southern China. ‘Brazil’ banana plantlets were exposed to 5 °C for 24 hours and then total crude protein was extracted from treatment and control leaves by phenol extraction, separated with two-dimensional gel electrophoresis, and subsequently identified by mass spectrometry (MS). Out of the more than 400 protein spots reproducibly detected, only 41 protein spots exhibited a change in intensity by at least 2-fold, with 26 proteins increasing and 15 proteins decreasing expression. Of these, 28 differentially expressed proteins were identified by MS. The identified proteins, including well-known and novel cold-responsive proteins, are involved in several cellular processes, including antioxidation and antipathogen, photosynthesis, chaperones, protein synthesis, signal transduction, energy metabolism, and other cellular functions. Proteins related to antioxidation, pathogen resistance, molecular chaperones, and energy metabolism were up-regulated, and proteins related to ethylene synthesis, protein synthesis, and epigenetic modification were down-regulated in response to cold temperature treatment. The banana plantlets incubated at cold temperatures demonstrated major changes in increased reactive oxygen species (ROS) scavenging, defense against diseases, and energy supply. Increased antioxidation capability in banana was also discovered in plantain, which has greater cold tolerance than banana in response to cold stress conditions. Therefore, we hypothesized that an increased antioxidation ability could be a common characteristic of banana and plantain in response to cold stress conditions. These findings may provide a better understanding of the physiological processes of banana in response to cold stress conditions.