IntroductionStripe rust is a global disease of wheat. Identification of new resistance genes is key to developing and growing resistant varieties for control of the disease. Wheat line PI 660122 has exhibited a high level of stripe rust resistance for over a decade. However, the genetics of stripe rust resistance in this line has not been studied. A set of 239 recombinant inbred lines (RILs) was developed from a cross between PI 660122 and an elite Chinese cultivar Zhengmai 9023.MethodsThe RIL population was phenotyped for stripe rust response in three field environments and genotyped with the Wheat 15K single-nucleotide polymorphism (SNP) array.ResultsA total of nine quantitative trait loci (QTLs) for stripe rust resistance were mapped to chromosomes 1B (one QTL), 2B (one QTL), 4B (two QTLs), 4D (two QTLs), 6A (one QTL), 6D (one QTL), and 7D (one QTL), of which seven QTLs were stable and designated as QYrPI660122.swust-4BS, QYrPI660122.swust-4BL, QYrPI660122.swust-4DS, QYrPI660122.swust-4DL, QYrZM9023.swust-6AS, QYrZM9023.swust-6DS, and QYrPI660122.swust-7DS. QYrPI660122.swust-4DS was a major all-stage resistance QTL explaining the highest percentage (10.67%–20.97%) of the total phenotypic variation and was mapped to a 12.15-cM interval flanked by SNP markers AX-110046962 and AX-111093894 on chromosome 4DS.DiscussionThe QTL and their linked SNP markers in this study can be used in wheat breeding to improve resistance to stripe rust. In addition, 26 lines were selected based on stripe rust resistance and agronomic traits in the field for further selection and release of new cultivars.

Male sterility is a valuable trait for watermelon breeding, as watermelon hybrids exhibit obvious heterosis. However, the underlying regulatory mechanism is still largely unknown, especially regarding the related non-coding genes. In the present study, approximately 1035 differentially expressed genes (DEGs), as well as 80 DE-lncRNAs and 10 DE-miRNAs, were identified, with the overwhelming majority down-regulated in male-sterile floral buds. Enrichment analyses revealed that the general phenylpropanoid pathway as well as its related metabolisms was predicted to be altered in a mutant compared to its fertile progenitor. Meanwhile, the conserved genetic pathway DYT1-TDF1-AMS-MS188-MS1, as well as the causal gene ClAMT1 for the male-sterile mutant Se18, was substantially disrupted during male reproductive development. In addition, some targets of the key regulators AMS and MS188 in tapetum development were also down-regulated at a transcriptional level, such as ABCG26 (Cla004479), ACOS5 (Cla022956), CYP703A2 (Cla021151), PKSA (Cla021099), and TKPR1 (Cla002563). Considering lncRNAs may act as functional endogenous target mimics of miRNAs, competitive endogenous RNA networks were subsequently constructed, with the most complex one containing three DE-miRNAs, two DE-lncRNAs, and 21 DEGs. Collectively, these findings not only contribute to a better understanding of genetic regulatory networks underlying male sterility in watermelon, but also provide valuable candidates for future research.

Nitrogen (N) and phosphorus (P) are essential phytomacronutrients, and deficiencies in these two elements limit growth and yield in apple (Malus domestica Borkh.). The rootstock plays a key role in the nutrient uptake and environmental adaptation of apple. The objective of this study was to investigate the effects of N and/or P deficiency on hydroponically-grown dwarfing rootstock ‘M9-T337’ seedlings, particularly the roots, by performing an integrated physiological, transcriptomics-, and metabolomics-based analyses. Compared to N and P sufficiency, N and/or P deficiency inhibited aboveground growth, increased the partitioning of total N and total P in roots, enhanced the total number of tips, length, volume, and surface area of roots, and improved the root-to-shoot ratio. P and/or N deficiency inhibited NO3 − influx into roots, and H+ pumps played a important role in the response to P and/or N deficiency. Conjoint analysis of differentially expressed genes and differentially accumulated metabolites in roots revealed that N and/or P deficiency altered the biosynthesis of cell wall components such as cellulose, hemicellulose, lignin, and pectin. The expression of MdEXPA4 and MdEXLB1, two cell wall expansin genes, were shown to be induced by N and/or P deficiency. Overexpression of MdEXPA4 enhanced root development and improved tolerance to N and/or P deficiency in transgenic Arabidopsis thaliana plants. In addition, overexpression of MdEXLB1 in transgenic Solanum lycopersicum seedlings increased the root surface area and promoted acquisition of N and P, thereby facilitating plant growth and adaptation to N and/or P deficiency. Collectively, these results provided a reference for improving root architecture in dwarfing rootstock and furthering our understanding of integration between N and P signaling pathways.

Glucose-6-phosphate dehydrogenase (G6PDH) is a key enzyme in the pentose phosphate pathway responsible for the generation of nicotinamide adenine dinucleotide phosphate (NADPH), thereby playing a central role in facilitating cellular responses to stress and maintaining redox homeostasis. This study aimed to characterize five G6PDH gene family members in maize. The classification of these ZmG6PDHs into plastidic and cytosolic isoforms was enabled by phylogenetic and transit peptide predictive analyses and confirmed by subcellular localization imaging analyses using maize mesophyll protoplasts. These ZmG6PDH genes exhibited distinctive expression patterns across tissues and developmental stages. Exposure to stressors, including cold, osmotic stress, salinity, and alkaline conditions, also significantly affected the expression and activity of the ZmG6PDHs, with particularly high expression of a cytosolic isoform (ZmG6PDH1) in response to cold stress and closely correlated with G6PDH enzymatic activity, suggesting that it may play a central role in shaping responses to cold conditions. CRISPR/Cas9-mediated knockout of ZmG6PDH1 on the B73 background led to enhanced cold stress sensitivity. Significant changes in the redox status of the NADPH, ascorbic acid (ASA), and glutathione (GSH) pools were observed after exposure of the zmg6pdh1 mutants to cold stress, with this disrupted redox balance contributing to increased production of reactive oxygen species and resultant cellular damage and death. Overall, these results highlight the importance of cytosolic ZmG6PDH1 in supporting maize resistance to cold stress, at least in part by producing NADPH that can be used by the ASA-GSH cycle to mitigate cold-induced oxidative damage.

Sclerotinia sclerotiorum is a plant pathogenic fungus that causes white mold or stem rot diseases. It affects mostly dicotyledonous crops, resulting in significant economic losses worldwide. Sclerotia formation is a special feature of S. sclerotiorum, allowing its survival in soil for extended periods and facilitates the spread of the pathogen. However, the detailed molecular mechanisms of how sclerotia are formed and how virulence is achieved in S. sclerotiorum are not fully understood. Here, we report the identification of a mutant that cannot form sclerotia using a forward genetics approach. Next-generation sequencing of the mutant’s whole genome revealed candidate genes. Through knockout experiments, the causal gene was found to encode a cAMP phosphodiesterase (SsPDE2). From mutant phenotypic examinations, we found that SsPDE2 plays essential roles not only in sclerotia formation, but also in the regulation of oxalic acid accumulation, infection cushion functionality and virulence. Downregulation of SsSMK1 transcripts in Sspde2 mutants revealed that these morphological defects are likely caused by cAMP-dependent inhibition of MAPK signaling. Moreover, when we introduced HIGS construct targeting SsPDE2 in Nicotiana benthamiana, largely compromised virulence was observed against S. sclerotiorum. Taken together, SsPDE2 is indispensable for key biological processes of S. sclerotiorum and can potentially serve as a HIGS target to control stem rot in the field.

Cucumber angular leaf spot (ALS) disease, caused by Pseudomonas amygdali pv. lachrymans (Pal), is an emerging disease with a high incidence that causes severe damage to cucumber worldwide. Bacterial aerosols play a crucial role in the epidemiology of greenhouse ALS disease. However, little is known about the influence of temperature and relative humidity (RH) on the dynamics of Pal in aerosols. A study was conducted to investigate the relationships between the concentration of Pal aerosols and their dependence on temperature and RH in aerosol chambers and greenhouses. The results demonstrated that temperature and RH are both significant factors influencing the release amount, survival time and infectivity of Pal in aerosols, while RH has a greater influence on particle size than temperature across the range of conditions tested. The release amount and survival time of Pal in aerosols under high RH (95%) and low temperature (≤ 25°C) conditions were significantly higher than those under low RH (35%) and high temperature (35°C) conditions. The highest release amount of Pal aerosol (96 CFU/m3) and highest survival rate (98.41%) were found at 18°C and 95% RH, while the highest disease index (DI = 60.9) caused by Pal aerosol was found at 25°C and 95% RH. In addition, Pal aerosols presented a larger diameter (4.7->7.0 μm) under high RH (95% RH) than under dry conditions (≤ 65% RH). These findings will play a crucial role in elucidating the influence of environmental parameters on the dynamics and transmission of Pal in aerosols. Based on our findings, preliminary recommendations for controlling airborne Pal spread involve controlling air temperature and RH, which will contribute to the effective alleviation and control of cucumber ALS disease.