Dutta Bhabesh, Gitaitis Ronald, Smith Samuel, Langston David
Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton, Georgia, United States of America.
PLoS One. 2014 Jun 17;9(6):e99215. doi: 10.1371/journal.pone.0099215. eCollection 2014.
The ability of seed-borne bacterial pathogens (Acidovorax citrulli, Clavibacter michiganensis subsp. michiganensis, Pseudomonas syringae pv. tomato, Xanthomonas euvesicatoria, and Pseudomonas syringae pv. glycinea) to infest seeds of host and non-host plants (watermelon, tomato, pepper, and soybean) and subsequent pathogen transmission to seedlings was investigated. A non-pathogenic, pigmented strain of Serratia marcescens was also included to assess a null-interacting situation with the same plant species. Flowers of host and non-host plants were inoculated with 1 × 10(6) colony forming units (CFUs)/flower for each bacterial species and allowed to develop into fruits or umbels (in case of onion). Seeds harvested from each host/non-host bacterial species combination were assayed for respective bacteria by plating on semi-selective media. Additionally, seedlots for each host/non-host bacterial species combination were also assayed for pathogen transmission by seedling grow-out (SGO) assays under greenhouse conditions. The mean percentage of seedlots infested with compatible and incompatible pathogens was 31.7 and 30.9% (by plating), respectively and they were not significantly different (P = 0.67). The percentage of seedlots infested with null-interacting bacterial species was 16.8% (by plating) and it was significantly lower than the infested lots generated with compatible and incompatible bacterial pathogens (P = 0.03). None of the seedlots with incompatible/null-interacting bacteria developed symptoms on seedlings; however, when seedlings were assayed for epiphytic bacterial presence, 19.5 and 9.4% of the lots were positive, respectively. These results indicate that the seeds of non-host plants can become infested with incompatible and null-interacting bacterial species through flower colonization and they can be transmitted via epiphytic colonization of seedlings. In addition, it was also observed that flowers and seeds of non-host plants can be colonized by compatible/incompatible/null-interacting bacteria to higher populations; however, the level of colonization differed significantly depending on the type of bacterial species used.
研究了种子携带的细菌病原体（西瓜嗜酸菌、密执安棒形杆菌密执安亚种、丁香假单胞菌番茄致病变种、辣椒疮痂病菌和大豆丁香假单胞菌）侵染寄主和非寄主植物（西瓜、番茄、辣椒和大豆）种子以及随后病原体向幼苗传播的能力。还纳入了一株非致病性的产色素粘质沙雷氏菌菌株，以评估与相同植物物种的零相互作用情况。对于每种细菌物种，以每朵花接种1×10⁶ 菌落形成单位（CFU）的量接种到寄主和非寄主植物的花朵上，并让其发育成果实或伞形花序（如洋葱的情况）。从每种寄主/非寄主细菌物种组合收获的种子通过接种在半选择性培养基上检测相应的细菌。此外，对于每种寄主/非寄主细菌物种组合的种子批，还通过温室条件下的幼苗生长试验（SGO）检测病原体传播情况。接种了亲和性和非亲和性病原体的种子批的平均百分比分别为31.7%和30.9%（通过平板接种法），且它们没有显著差异（P = 0.67）。接种了零相互作用细菌物种的种子批的百分比为16.8%（通过平板接种法），且显著低于由亲和性和非亲和性细菌病原体产生的受侵染种子批（P = 0.03）。没有任何接种了非亲和性/零相互作用细菌的种子批在幼苗上出现症状；然而，当检测幼苗上的附生细菌存在情况时，分别有19.5%和9.4%的种子批呈阳性。这些结果表明，非寄主植物的种子可通过花定殖而被非亲和性和零相互作用细菌物种侵染，并且它们可通过幼苗的附生定殖进行传播。此外，还观察到非寄主植物的花朵和种子可被亲和性/非亲和性/零相互作用细菌定殖到更高的种群数量；然而，定殖水平根据所使用的细菌物种类型而有显著差异。
