With global warming, heat stress has become an important factor that seriously affects crop yield and quality. Therefore, understanding plant responses to heat stress is important for agricultural practice, but the molecular mechanism of high-temperature tolerance in garlic remains unclear. In this study, ‘Xusuan No. 6’ was used as the experimental material. After heat stress for 0 (CK), 2 and 24 h, transcriptome sequencing was used to screen metabolic pathways and differentially expressed genes (DEGs) closely related to heat stress and was further verified by quantitative real-time polymerase chain reaction (qRT-PCR). A total of 86,110 unigenes obtained from the raw transcriptome sequencing data were spliced. After 2 h of heat treatment, the expression levels of 8898 genes increased, and 3829 genes were decreased in leaves. After 24 h, the expression levels of 7167 genes were upregulated, and 3176 genes were downregulated. Gene Ontology enrichment analysis showed that DEGs were mainly enriched in seven categories: cellular processes, metabolic processes, binging, catalytic activity, cellular anatomical entity and protein-containing complex response to stimulus. Kyoto Encyclopedia of Genes and Genomes pathway enrichment showed that DEGs are involved in protein processing in the endoplasmic reticulum, plant hormone signal transduction, phenylpropanoid biosynthesis, and photosynthetic antenna proteins. Six genes were selected and further verified by qRT-PCR. In this study, the full-length transcriptome of garlic was constructed, and the regulatory genes related to the heat resistance of garlic were studied. Taken together, these findings can provide a theoretical basis for the cloning of heat resistance genes in garlic and for the analysis of heat resistance mechanisms.

This study aimed to explore the impact paths on soil organic carbon and crop yield of completely or partially substituting chemical N fertilizer with organic fertilizers. A four-year field experiment was conducted and included four treatments: (i) N0, no N fertilization application; (ii) NF, only synthetic N fertilizer application; (iii) 1/2OF, organic fertilizer substituted for 100% of the synthetic N fertilizer, with the total N application amount being equivalent to half that of NF; and (iv) 1/3OF + 2/3NF, organic fertilizer substituted for 1/3 of the synthetic N fertilizer with the total N application amount from organic and synthetic fertilizer being equivalent to that of NF. Soil total organic carbon (TOC), labile organic-carbon fractions (microbial biomass carbon (MBC), dissolved organic carbon (DOC), particulate organic carbon (POC), and easily oxidized organic carbon (EOC)), the carbon pool management index (CPMI), soil aggregated distribution, and water-stable aggregate-associated organic carbon were determined. Structural equation modeling (SEM) was used to clarify the impact paths of TOC and garlic yield changes under different N fertilizer treatments. Results showed that compared with N0 and NF, 1/2OF and 1/3OF + 2/3NF significantly increased TOC contents by 14.1–20.6%. Soil MBC, DOC, and EOC under 1/2OF were significantly higher than under N0, whereas the 1/3OF + 2/3NF treatment had significantly greater POC. The CPMI was improved by organic fertilizer treatment, with 1/2OF treatment being significantly higher than N0 and NF. The proportion of soil aggregate mass with particle sizes >2 mm was significantly greater under N0, while 1/3OF + 2/3NF significantly increased the proportion of particle sizes of 0.5–2 mm. Soil water-stable aggregate-associated organic carbon showed a trend of first increasing and then decreasing, with the largest particle sizes being 1–2 mm. Moreover, organic fertilizer significantly increased soil water-stable aggregate organic carbon compared with N0 and NF. Similarly, the garlic yield increased with organic fertilizer treatment, while 1/3OF + 2/3NF significantly increased the yield by 37.2% and 15.3%, respectively, compared with N0 and NF. Furthermore, SEM analysis indicated that fertilizer regimes could directly affect TOC and labile organic carbon components by affecting aggregate-associated organic carbon. In particular, aggregates with particle sizes of 0.5–2 mm played an important role, indirectly affecting garlic yield and CPMI. These results indicate that organic fertilizer application has the potential to improve soil organic-carbon content and garlic yield; moreover, fully applying organic fertilizer can reduce N fertilizer input while still maintaining an increase in soil organic carbon and crop yield in the short term. However, caution is still needed regarding of the type and quantity of organic fertilizer added in different cropping systems, and with different soil textures.

The heat shock transcription factor (HSF) family is one of the most widely studied transcription factor families in plants; HSFs can participate in the response to various stressors, such as heat stress, high salt, and drought stress. Based on garlic transcriptome data, we screened and identified 22 garlic HSFs. The HSF proteins of garlic and Arabidopsis can be divided into three (A, B, C) subfamilies. The phylogenetic relationship, chromosome localization, sequence characteristics, conserved motifs, and promoter analysis of the HSF family were analyzed through bioinformatics methods. RT-qPCR analysis showed that the nine selected genes had different degrees of response to heat stress. In addition, we isolated and identified a class B HSF gene, AsHSFB1, from garlic variety ‘Xusuan No.6’. Subsequently, the AsHSFB1 gene was overexpressed in Arabidopsis thaliana. Under heat stress, the germination rate and growth of wild-type plants were better than that of transgenic plants. Moreover, after heat treatment, the contents of peroxidase, catalase, and chlorophyll a and b of transgenic plants were lower, but the contents of malondialdehyde (MDA) and leaf conductivity were higher. Nitroblue tetrazolium (NBT) staining showed that the stained area of transgenic plant leaves was larger than that of the wild type. Further studies showed that AsHSFB1 overexpression inhibited the expression of related reverse resistance genes. These results indicate that AsHSFB1 might play a negative regulatory role in garlic resistance under high stress. Altogether, these findings provide valuable data for revealing the function of HSF genes and lay a foundation for the subsequent selection of heat-resistant garlic varieties.

WRKY transcription factors (TFs) are primarily involved in regulating the response of plants to different types of abiotic stress and related physiological processes. WRKY genes have yet to be characterized in garlic (Allium sativum L.), which is in the family Alliaceae. Here, 78 WRKY TFs were identified based on the garlic transcriptome and genome. They were divided into seven subfamilies based on Arabidopsis thaliana WRKY domains. Cis-element analysis revealed that the WRKY family members have ABRE and MBS cis-response elements that respond to salt stress, gibberellins, and drought stress. Real-time quantitative polymerase chain reaction (RT-qPCR) analysis revealed that the expression of nine WRKY genes was induced under heat and salt stress.