The Mildew Resistance Locus (Mlo) gene family is reported in various species as regulators of powdery mildew (PM) resistance. However, the Mlo genes in cucurbit crops remain limited. In this study, a genome-wide investigation of Mlo genes was conducted in eight Cucurbitaceae species and in rice, maize, arabidopsis, and barley, and a total of 202 Mlo genes were identified. The phylogenetic analysis showed that 202 Mlo genes can be classified into six clades, and the Mlo genes from clades I and III are likely pivotal in regulating PM resistance in dicotyledonous and monocotyledonous plants, respectively. The Ka/Ks ratios for these homologous Mlo gene pairs ranged from 0 to 0.6, revealing that they underwent substantial purifying selection during evolution. Among 12 crops, there were the most Mlo genes (22 Cm-mlo) in melon. An expression analysis revealed that six Cm-mlo genes showed expression responses to PM infection in which Cm-mlo38 and Cm-mlo44 were phylogenetically close to Mlo genes that regulated PM resistance. Using the VIGS system for silencing, Cm-mlo38 and Cm-mlo44 enhanced resistance to PM in susceptible material. A protein interaction analysis indicated that Cm-mlo38 might regulate PM resistance through interactions with PR5 and CML proteins. These results provide a comprehensive understanding of the Mlo family in Cucurbitaceae and pave the way for future functional analysis and genetic improvement for improving PM resistance in Cucurbitaceae.

Studying the interrelationship between agroecosystems and the microbiome is essential in achieving sustainable agricultural development. In particular, the relationship between the rhizosphere microbiome and crops is critical to the health and stability of agroecosystems. This study evaluated the diversity and keystone species of the cucumber rhizosphere microbiome and investigated their contributing role in cucumber growth and microbial community regulation. A total of 108 soil samples were collected from the rhizosphere and bulk soil of cucumber crops in different locations and under different cultivation modes in a high-yield area. These samples were analyzed to study the interrelationships between different cultivation modes and crop rhizosphere microorganisms. The results revealed significant regional differences in microbial communities due to microhabitat (rhizosphere and bulk soil) and geographic location. Common bacteria such as Pseudomonas, Sphingomonas, Lysobacter and Rhodanobacter were the most abundant and showed strong correlations with several other bacteria through co-occurrence networking. In addition, Flavobacterium sp. and Bacillus sp. were identified as keystone species for the rhizobia community structure. Synthetic microbial communities and pot experiments confirmed that these two keystone species could enrich the soil microbime and promote cucumber growth. Flavobacterium sp. may promote cucumber growth by regulating the rhizosphere microbial community while Bacillus sp. may influence cucumber growth by stabilizing the rhizosphere microbial biomass, further enhancing nutrient cycling efficiency and improving system stability, which in turn affected the agroecosystem. Our study demonstrates that specific keystone species are important in shaping the cucumber rhizosphere microbiome and plant growth. These results provide insights into agroecosystem-microbe interrelationships and provide a potential basis for optimizing agricultural management strategies.