Bacillus subtilis NCD-2 demonstrates exceptional biocontrol potential against cotton Verticillium wilt. While previous studies have established its direct antifungal activity (e.g., inhibiting Verticillium dahliae mycelial growth and spore germination), our work reveals a novel mechanism: NCD-2 primes systemic resistance in cotton by activating plant immune-signaling pathways. Firstly, transcriptional profiling uncovered that NCD-2 triggers a defense response in roots analogous to V. dahliae infection, allowing cotton to maintain a more balanced state when confronted with pathogen attacks. Meanwhile, the mutant strains ∆fen and ∆srf—defective in lipopeptide synthesis—also improved cotton resistance to Verticillium wilt by activating partially identical defense pathways in cotton roots. Furthermore, the application of lipopeptide compounds derived from NCD-2, particularly surfactin and fengycin, could enhance host resistance to V. dahliae. Using an RT-qPCR approach, we found that numerous resistance-related genes were induced by these lipopeptide compounds. The up-regulation of SA/JA pathway markers (e.g., NPR1, ICS1, COI1, and LOX1) revealed NCD-2’s activation of plant immune signaling. Using virus-induced gene silencing (VIGS), we conclusively linked SA and JA signaling to NCD-2-induced defense priming. Silencing either pathway abolished resistance, highlighting their indispensable coordination. By bridging mechanistic insights and agricultural applicability, our work positions NCD-2 as a sustainable alternative to conventional fungicides, addressing both crop productivity and environmental health.

Pear black spot disease is a serious fungal disease during pear production; salicylic acid is a core signaling molecule that regulates the expression of plant disease resistance genes. To elucidate the intrinsic association between salicylic acid-induced resistance to pear black spot disease and lignin biosynthesis, in vitro plantlets of two pear cultivars, ‘Xinli No.7’ and ‘Xueqing’, were employed as experimental materials. After 60 h SA pretreatment, the leaves were inoculated with the pathogen Alternaria alternata. Leaf samples were harvested at 0, 8, 16, 24, and 48 h post-inoculation to determine phenylalanine ammonia-lyase activity, quantify lignin content, and analyze the transcript levels of genes involved in lignin synthesis. The results demonstrated that, relative to the untreated control group, SA treatment significantly enhanced phenylalanine ammonia-lyase activity and promoted lignin accumulation in both ‘Xinli No.7’ and ‘Xueqing’. Moreover, multiple key genes associated with lignin biosynthesis—including PbrPAL1, Pbr4CL1, PbrCOMT, PbrCCoAOMT, PbrCAD, and PbrPOD—were markedly upregulated, with their expression levels increasing by 3.5–15 fold. Transcript profiles of PbrHCT1, PbrHCT4, and PbrC3H1 exhibited cultivar-specific divergence between the two varieties. Notably, the susceptible cultivar ‘Xueqing’ displayed a distinct lag phase and attenuated response in the expression of all lignin-related genes compared with the other cultivar. This study provides reference for green prevention and sustainable development of pear.

The ‘Yuluxiang’ pear is a key cultivated variety in China, celebrated for its high quality. However, it exhibits a low leaf regeneration frequency of only 35.0%, which hinders its transgenic breeding process. To establish an efficient regeneration system, we utilized tissue culture seedlings of the ‘Yuluxiang’ pear and investigated various factors influencing leaf regeneration: plant growth regulators, natural organic materials, leaf wounding and positioning methods, duration of dark culture, ages and lines of plantlets, as well as culture containers. Our results indicated that the optimal medium for leaf regeneration consisted of MS supplemented with 6-BA (6-Benzyl Aminopurine) 1.5 mg/L, NAA (α-Naphthalene acetic acid) 0.4 mg/L along with 10% (v/v) coconut water. Suitable wounding involved ensuring no damage to leaves while placing the abaxial side facing down on the medium; the ideal duration for dark culture was determined to be 21 days; optimal plantlet age was found to be 20 days; both plantlet line 1 and line 2 demonstrated effectiveness; triangle bottles were identified as appropriate culture containers. In summary, we successfully established an efficient leaf regeneration system for the ‘Yuluxiang’ pear that achieved a maximum regeneration frequency of 96.70% with an average bud number of 5.15 per explant. This system also proved effective for the ‘Qiuyue’ pear, yielding a regeneration frequency of 88.89% and an average bud number of 3.44 per explant. After investigating the germination methods of 200 leaves from this screened leaf regeneration system of ‘Yuluxiang’, it was found that there were both direct and indirect regeneration methods, and the germination rate of direct and indirect regeneration was 68.00% and 70.50%, respectively. Therefore, this study also laid a solid foundation for the future genetic transformation of ‘Yuluxiang’ pear.