本研究以矮化梨品种‘601D’及其突变体‘601T’为材料，研究比较了它们的生物学特性，并进一步探讨了601D的矮化机理。生物学特性表明，601D的节间短，树体短而紧凑，叶片厚而宽，气孔密度低，气孔（直径）大，光合能力强。601T的生物学特性表现出显著的差异。内源激素检测结果表明，601D的脱落酸（ABA）、ABA葡萄糖酯和GA4含量较高，而反式玉米素含量较低。通过转录组学分析，发现ABA的生物合成和代谢途径存在显著差异。相关转录因子如bHLH、WRKY和Homeobox等也参与了植物矮化的调控。因此，我们研究了三种与601T有明显差异的激素，发现只有ABA可以诱导601T恢复矮化植株表型。因此，我们认为601D的矮化是由于ABA的过度积累所致。本研究为矮化品种的选育提供了新的理论依据。

Citrus canker, an epidemic quarantine disease caused by Xanthomonas axonopodis pv. citri, has brought a great damage in citrus production worldwide. Herein, a rice PRR (pattern recognition receptor) gene Xa21 together with GUS reporter gene and hygromycin phosphotransferase gene (HPT) was introduced into Anliucheng sweet orange (Citrus sinensis Osbeck) via Agrobacterium-mediated transformation of embryogenic callus. The transgenic calluses were screened on MT basal medium containing hygromycin (HYG) and detected by histochemical GUS staining. The transgenic plantlets were recovered through somatic embryogenesis pathway. The regenerated plantlets were accustomed to and maintained in the greenhouse. The transgene integration of recovered plantlets was identified by PCR and Southern blot hybridization. It showed that all the transgenic plantlets tested had undergone single copy integration, the expression of Xa21 in eight different transgenic lines detected by qRT-PCR can be divided into three grades, high for T5 and T6, middle for T4 and low for the rest. The tolerance to citrus canker disease of the three recovered transgenic lines T2, T4 and T6 was assessed by in vitro pin-puncture inoculation. The results showed that all the three transgenic lines conferred improved resistance to citrus canker bacterium infection and the T4 transgenic line displayed the highest resistance. The mechanism and feasibility of rice Xa21 in triggering innate immunity in citrus was briefly discussed.