Phosphorus utilization by crop plants is often limited, thereby resulting in large accumulations of residual phosphorus fertilizer in the soil. Trichoderma fungi function as natural decomposition agents that can contribute to increasing decomposition and promoting nutrient absorption in plants. In this study, we developed a novel fertilizer application strategy that reduces phosphate fertilizer and increases Trichoderma and examined its effects on the growth, nutrient absorption, and fruit quality of pepper (Capsicum annuum L.). We compared the efficacies of eight treatments: P100 = standard dose application of phosphorus fertilizer; P85 = 85% dose; P70 = 70% dose; P0 = no phosphorus fertilizer; and the TP100, TP85, TP70, and TP0 treatments, in which a Trichoderma mixture was added to the P100, P85, P70, and P0 treatments, respectively. The combined fertilizer application strategy stimulated plant growth, increased chlorophyll content, improved yield, and enhanced nutrient absorption. Additionally, the strategy improved pepper fruit quality by increasing the contents of soluble proteins, soluble sugars, vitamin C, capsaicin, and capsanthin. A comprehensive analysis indicated that the TP85 treatment was the optimal fertilization regime for pepper. This study provides a novel fertilizer application strategy for pepper that not only ensures good plant growth but also protects soil health.

Cucumbers (Cucumis sativus L.) are a global popular vegetable and are widely planted worldwide. However, cucumbers are susceptible to various infectious diseases such as Fusarium and Verticillium wilt, downy and powdery mildew, and bacterial soft rot, which results in substantial economic losses. Grafting is an effective approach widely used to control these diseases. The present study investigated the role of wax and the phenylpropanoid biosynthesis pathway in black-seed pumpkin rootstock-grafted cucumbers. Our results showed that grafted cucumbers had a significantly higher cuticular wax contents on the fruit surface than that of self-rooted cucumbers at all stages observed. A total of 1132 differently expressed genes (DEGs) were detected in grafted cucumbers compared with self-rooted cucumbers. Pathway enrichment analysis revealed that phenylpropanoid biosynthesis, phenylalanine metabolism, plant circadian rhythm, zeatin biosynthesis, and diterpenoid biosynthesis were significantly enriched. In this study, 1 and 13 genes involved in wax biosynthesis and the phenylpropanoid biosynthesis pathway, respectively, were up-regulated in grafted cucumbers. Our data indicated that the up-regulated genes in the wax and phenylpropanoid biosynthesis pathways may contribute to disease resistance in rootstock-grafted cucumbers, which provides promising targets for enhancing disease resistance in cucumbers by genetic manipulation.

Powdery mildew (PM), a common disease of many major crop species, including melon (Cucumis melo L.), affects plant growth and fruit quality and seriously reduces production. Using a combined morphological and molecular approach, we attribute the PM pathogen that naturally occurs in melon to Podosphaera xanthii, and specifically to physiological race 1. An investigation into the genetic basis of PM resistance in melon using the resistant accession ‘PI 164637’ and susceptible counterpart ‘HDZ’ reveals dominant inheritance of PM resistance at the seedling stage, supported by F₂ and backcross population segregation ratios. Adult plant assessments indicate a major gene with an additive effect for PM resistance. Bulk segregant analysis coupled with high-throughput sequencing identified a significant quantitative trait locus on chromosome 6 that is associated with PM resistance. Genetic mapping narrowed down the candidate region to 63.5 kb using InDel molecular markers, harboring 12 candidate genes. The marker chr06_indel_5 047 127 demonstrated high accuracy in screening PM resistance in an F₂ segregating population and 30 inbred lines as natural populations. Functional annotation and expression analysis of candidate genes revealed that MYB transcription factor MELO3C006700, GATA transcription factor MELO3C028829 and heparanase-like protein MELO3C006697 are promising candidate genes for PM resistance in melon. The genetic architecture underlying this resistance in melon offers valuable insights for breeding programs, and the identified markers, especially chr06_indel_5 047 127, may enable practical applications for marker-assisted selection in developing PM-resistant melon varieties.

Melon fruit cracking reduces yield, increases transportation costs, and shortens shelf life, which makes the development of cracking-resistant varieties crucial for the industry’s advancement. This study investigated the pathways and genes related to melon fruit cracking through cell morphology observation, endogenous hormone analyses, and transcriptome analysis of two contrasting advanced inbred lines, the extremely crack-resistant line R2 and the crack-susceptible line R6. R2 has small, tightly packed epidermal cells with a thick cuticle, while R6 has larger, more loosely arranged epidermal cells and a significantly thinner cuticle. Hormonal analysis revealed significant differences in abscisic acid, cytokinin, gibberellin, auxin, and salicylic acid contents between R2 and R6 at various fruit developmental stages. The abscisic acid and salicylic acid content in R2 were 1.9–5.2 times and 1.5–3.6 times higher than those in R6, respectively, whereas the gibberellin content in R6 was 1.5–2.3 times higher than that in R2. Pericarp transcriptome analysis identified 4281, 6242, and 6879 differentially expressed genes (DEGs) at 20, 30, and 40 days after anthesis, respectively. Among these, 47 DEGs related to phenylpropanoid biosynthesis (ko00940) and 79 DEGs involved in plant hormone signal transduction (ko04075) were differentially expressed at two or more stages. WGCNA analysis identified six core hub genes that potentially play a role in regulating melon fruit cracking. These findings lay a foundation for further studies on the functional roles of crack-resistant genes and the breeding of crack-tolerant varieties.