Salinity poses a significant environmental challenge, limiting plant growth and development. To cultivate salt-tolerant plants, it is crucial to understand the physiological, biochemical, and molecular responses and adaptations to salt stress, as well as to explore natural genetic resources linked to salt tolerance. In this review, we provide a detailed overview of the mechanisms behind morphological and physiological responses triggered by salt stress, including salt damage to plants, the disturbance of cell osmotic potentials and ion homeostasis, lipid peroxidation, and the suppression of photosynthesis and growth. We also describe the physiological mechanisms that confer salt tolerance in plants, such as osmotic adjustments, reactive oxygen species (ROS) scavenging, photosynthetic responses, phytohormone regulation, and ion regulation. Additionally, we summarize the salt-stress sensing and signaling pathways, gene regulatory networks, as well as salt-tolerance mechanisms in plants. The key pathways involved in salt-stress signal perception and transduction, including Ca²⁺-dependent protein kinase (CDPK) cascades, the salt overly sensitive (SOS) pathway, and the abscisic acid (ABA) pathway, are discussed, along with relevant salt-stress-responsive genes and transcription factors. In the end, the important issues and challenges related to salt tolerance for future research are addressed. Overall, this review aims to provide essential insights for the future cultivation and breeding of crops and fruits.

Pomegranate (Punica granatum L.) is widely grown in arid and semiarid regions, where the salinization may have developed through irrigation. A greenhouse experiment was conducted to investigate NaCl stress on growth, photosynthesis, and nutrients of 18 pomegranate cultivars. One group was irrigated twice a week with a nutrient solution. The other group was watered twice a week with the same nutrient solution and 200 mM NaCl for five weeks. Dry weight, shoot length, new shoot number, root length and number, leaf area, leaf relative water content, and net photosynthesis of salt-treated plants were negatively impacted by salt stress, and there was a significant difference among cultivars. Few foliar damages were observed. Na content of plants significantly increased in all cultivars, while P, S, K, Ca, Mg, Si, Al, Zn content of plants decreased under salt stress. Fe, Mn, and Cu content increased in most cultivars. Pomegranate accumulated supraoptimal Na mostly in roots and transported more K and Ca to shoots, which was attributed to maintaining a higher ratio of K/Na and Ca/Na in the aerial part of plants. Ten of the 18 cultivars were considered salt-tolerant, which would offer a reference for pomegranate cultivation on saline lands.

Pomegranate (Punica granatum L.) is widely grown in arid and semi-arid soils, with constant soil salinization. To elucidate its molecular responses to salt stress on mRNA levels, we constructed 18 cDNA libraries of pomegranate roots and leaves from 0 (controls), 3, and 6 days after 200 mM NaCl treatment. In total, we obtained 34,047 genes by mapping to genome, and then identified 2255 DEGs (differentially expressed genes), including 1080 up-regulated and 1175 down-regulated genes. We found that the expression pattern of most DEGs were tissue-specific and time-specific. Among root DEGs, genes associated with cell wall organization and transmembrane transport were suppressed, and most of metabolism-related genes were over-represented. In leaves, 41.29% of DEGs were first suppressed and then recovered, including ions/metal ions binding-related genes. Also, ion transport and oxidation-reduction process were restricted. We found many DEGs involved in ABA, Ca²⁺-related and MAPK signal transduction pathways, such as ABA-receptors, Ca²⁺-sensors, MAPK cascades, TFs, and downstream functional genes coding for HSPs, LEAs, AQPs and PODs. Fifteen genes were selected to confirm the RNA-seq data using qRT-PCR. Our study not only illuminated pomegranate molecular responses to salinity, but also provided references for selecting salt-tolerant genes in pomegranate breeding processes.

Pomegranate (Punica granatum) flowers are classified as bisexual flowers and functional male flowers. Functional male flowers have sterile pistils that show abnormal ovule development. In previous studies, we identified INNER NO OUTER (INO), CRABS CLAW (CRC), and BELL1 (BEL1), which were specifically expressed in bisexual and functional male flowers. However, the functions of ovule identity genes and the mechanism underlying ovule sterility in pomegranate remain unknown. Here, we found that the integument primordia formed and then ceased developing in the ovules of functional male flowers with a vertical diameter of 8.1–13.0 mm. Megaspore mother cells were observed in bisexual flowers when the vertical diameters of flowers were 10.1–13.0 mm, but not in functional male flowers. We analyzed the expression patterns of ovule-related genes in pomegranate ovule sterility and found that PgCRC mRNA was highly expressed at a critical stage of ovule development in bisexual flowers. Ectopic expression of PgCRC and PgINO was sufficient to increase seed number in transgenic lines. PgCRC partially complemented the Arabidopsis (Arabidopsis thaliana) crc mutant, and PgINO successfully rescued the seeds set in the Arabidopsis ino mutant. The results of yeast two-hybrid assays, bimolecular fluorescence complementation assays, and genetic data analyses showed that PgCRC and PgINO directly interact with PgBEL1. Our results also showed that PgCRC and PgINO could not interact directly with MADS-box proteins and that PgBEL1 interacted with SEPALLATA proteins. We report the function of PgCRC and PgINO in ovule and seed development and show that PgCRC and PgINO interact with PgBEL1. Thus, our results provide understanding of the genetic regulatory networks underlying ovule development in pomegranate.

Chestnut (Castanea spp., Fagaceae family) is an economically and ecologically valuable species. The main goals of chestnut production vary among species and countries and depend on the ecological characteristics of orchards, agronomic management, and the architecture of chestnut trees. Here, we review recent research on chestnut trees, including the effects of fungal diseases (Cryphonectria parasitica and Phytophthora cinnamomi) and insect pests (Dryocosmus kuriphilus Yasumatsu), molecular markers for breeding, ecological effects, endophytic fungi, and extracts with human health benefits. We also review research on chestnut in the food science field, technological improvements, the soil and fertilizer used for chestnut production, and the postharvest biology of chestnut. We noted differences in the factors affecting chestnut production among regions, including China, the Americas, and Europe, especially in the causal agents of disease and pests. For example, there is a major difference in the resistance of chestnut to C. parasitica in Asian, European, and American countries. Our review provides new insights into the integrated disease and pest management of chestnut trees in China. We hope that this review will foster collaboration among regions and help to clarify differences in the direction of breeding efforts among countries.

Crapemyrtle bark scale (CMBS; Acanthococcus lagerstroemiae) is an exotic pest species that causes aesthetic and economic damage to crapemyrtles and poses potential threats to other horticultural crops in the United States. Although previous studies reported the infestation of CMBS on several alternative hosts across multiple families in Asia, its potential threats to other documented alternative hosts remain elusive and yet to be confirmed. In this study, feeding preference studies of CMBS were conducted on forty-nine plant species and cultivars in 2016 and 2019, in order to gain insight into the expansion of CMBS distribution in the United States, as well as other regions of the world. The infestations of CMBS were confirmed on apple (Malus domestica), Chaenomeles speciosa, Disopyros rhombifolia, Heimia salicifolia, Lagerstroemia ‘Spiced Plum’, M. angustifolia, and twelve out of thirty-five pomegranate cultivars. However, the levels of CMBS infestation on these test plant hosts in this study is very low compared to Lagerstroemia, and may not cause significant damage. No sign of CMBS infestation was observed on Rubus ‘Arapaho’, R. ‘Navaho’, R. idaeus ‘Dorman Red’, R. fruticosus, B. microphylla var. koreana × B. sempervirens, B. harlandii, or D. virginiana.