Nishijima K A, Alvarez A M, Hepperly P R, Shintaku M H, Keith L M, Sato D M, Bushe B C, Armstrong J W, Zee F T
Pacific Basin Agricultural Research Center (PBARC), USDA-ARS, P.O. Box 4459, Hilo, HI 96720.
University of Hawaii-Manoa, Honolulu 96822.
Plant Dis. 2004 Dec;88(12):1318-1327. doi: 10.1094/PDIS.2004.88.12.1318.
Edible ginger is a popular spice crop that is grown in Hawaii primarily for the fresh market, and as such, rhizome quality is of paramount importance. In our studies, a Gram-negative, facultative anaerobic, rod-shaped bacterium was consistently isolated from decayed as well as symptomless ginger rhizomes. The bacterium was identified as Enterobacter cloacae by biochemical assays and 16S rDNA sequence analysis. Rot symptoms, which usually occurred in the central cylinder of the rhizome, were characterized by yellowish-brown to brown discolored tissue and firm to spongy texture. In inoculation experiments, ginger strains of E. cloacae produced basal stem and root rot, with foliar chlorosis and necrosis in tissue-cultured ginger plantlets, and discolored and spongy tissue in mature ginger rhizome slices and whole segments. In other hosts, ginger strains of E. cloacae caused internal yellowing of ripe papaya fruit and internal rot of onion bulbs. All strains that caused symptoms in inoculated plants were reisolated and identified as E. cloacae. Our studies suggest that E. cloacae can exist as an endophyte of ginger rhizomes, and under conditions that are favorable for bacterial growth, or host susceptibility, including maturity of tissues, rhizome rot may occur. Rhizome quality may be impacted by the presence of E. cloacae under conditions such as high temperature, high relative humidity, and low oxygen atmosphere that may affect the development of decay, and such conditions should be avoided during post-harvest handling and storage. The association of E. cloacae with a rhizome rot of ginger is a new finding.
食用姜是一种广受欢迎的香料作物，在夏威夷主要种植用于鲜销市场，因此，根茎质量至关重要。在我们的研究中，一种革兰氏阴性、兼性厌氧、杆状细菌始终能从腐烂以及无症状的姜根茎中分离出来。通过生化分析和16S rDNA序列分析，该细菌被鉴定为阴沟肠杆菌。腐烂症状通常发生在根茎的中柱，其特征为组织呈黄棕色至棕色变色，质地坚硬至海绵状。在接种实验中，阴沟肠杆菌的姜菌株导致组培姜苗基部茎和根腐烂，叶片出现黄化和坏死，成熟姜根茎切片和整段出现变色和海绵状组织。在其他寄主中，阴沟肠杆菌的姜菌株导致成熟木瓜果实内部发黄和洋葱鳞茎内部腐烂。所有在接种植物中引起症状的菌株都被重新分离并鉴定为阴沟肠杆菌。我们的研究表明，阴沟肠杆菌可以作为姜根茎的内生菌存在，在有利于细菌生长或寄主易感性的条件下，包括组织成熟度，可能会发生根茎腐烂。在高温、高相对湿度和低氧气氛等可能影响腐烂发展的条件下，阴沟肠杆菌的存在可能会影响根茎质量，在收获后处理和储存过程中应避免此类条件。阴沟肠杆菌与姜根茎腐烂的关联是一项新发现。
