Apple leaf spot caused by the Alternaria alternata f. sp. mali (ALT1) fungus is one of the most devastating diseases of apple (Malus × domestica). We identified a hairpin RNA (hpRNA) named MdhpRNA277 that produces small RNAs and is induced by ALT1 infection in 9Golden Delicious9 apple. MdhpRNA277 produces mdm-siR277-1 and mdm-siR277-2, which target five resistance (R) genes that are expressed at high levels in resistant apple variety 9Hanfu9 and at low levels in susceptible variety 9Golden Delicious9 following ALT1 infection. MdhpRNA277 was strongly induced in 9Golden Delicious9 but not 9Hanfu9 following ALT1 inoculation. MdhpRNA277 promoter activity was much stronger in inoculated 9Golden Delicious9 vs. 9Hanfu9. We identified a single nucleotide polymorphism (SNP) in the MdhpRNA277 promoter region between 9Golden Delicious9 (pMdhpRNA277-GD) and 9Hanfu9 (pMdhpRNA277-HF). The transcription factor MdWHy binds to pMdhpRNA277-GD, but not to pMdhpRNA277-HF. Transgenic 9GL-39 apple expressing pMdhpRNA277-GD:MdhpRNA277 was more susceptible to ALT1 infection than plants expressing pMdhpRNA277-HF:MdhpRNA277 due to induced mdm-siR277 accumulation and reduced expression of the five target R genes. We confirmed that the SNP in pMdhpRNA277 is associated with Alternaria leaf spot resistance by crossing. This SNP could be used as a marker to distinguish between apple varieties that are resistant or susceptible to Alternaria leaf spot.

Aroma plays a crucial role in assessing the flavor quality of cherry fruits. This study compared the odor and volatile profiles of 37 cherry germplasm fruits using an electronic nose (E-nose) combined with headspace solid-phase microextraction-gas chromatography–mass spectrometry (HS-SPME-GC–MS). Notably, Cao5 exhibited a distinct odor compared to the other 36 sweet cherry cultivars. A total of 363 volatiles were identified and categorized into 14 classes. In terms of quantity, the top three categories of volatiles were terpenoids, esters, and alcohols. Among the samples, Saylor displayed the highest total volatile content at 76.98 μg∙g⁻¹, whereas Minnie Royal had the lowest at 67.27 μg∙g⁻¹. A total of 51 volatiles, including 1-nonen-3-one, 2-nonenal, (E)-, 2-nonenal, 2,4-nonadienal, and 2-hexenal, (E)-, were identified as the primary contributors to the aroma. In conclusion, this study aims to establish a foundation for rapidly and accurately evaluating cherry fruit flavor and developing new cultivars.

An F-box protein contributes to the self-compatibility of sweet cherry ‘Lapins’.

Long non-coding RNAs (lncRNAs), a class of important regulatory factors for many biological processes in plants, have received much attention in recent years. To explore the molecular roles of lncRNAs in sweet cherry fruit ripening, we conducted widely targeted metabolome, transcriptome and lncRNA analyses of sweet cherry fruit at three ripening stages (yellow stage, pink stage, and dark red stage). The results show that the ripening of sweet cherry fruit involves substantial metabolic changes, and the rapid accumulation of anthocyanins (cyanidin 3-rutinoside, cyanidin 3-O-galactoside, and cyanidin 3-O-glucoside) is the main cause of fruit coloration. These ripening-related alterations in the metabolic profile are driven by specific enzyme genes related to the synthesis and decomposition of abscisic acid (ABA), cell wall disintegration, and anthocyanin biosynthesis, as well as transcription factor genes, such as MYBs, bHLHs, and WD40s. LncRNAs can target these ripening-related genes to form regulatory modules, incorporated into the sweet cherry fruit ripening regulatory network. Our study reveals that the lncRNA-mRNA module is an important component of the sweet cherry fruit ripening regulatory network. During sweet cherry fruit ripening, the differential expression of lncRNAs will meditate the spatio-temporal specific expression of ripening-related target genes (encoding enzymes and transcription factors related to ABA metabolism, cell wall metabolism and anthocyanin metabolism), thus driving fruit ripening.