The long-term colonization dynamics of endophytic bacteria in cucumber plants, and their effects on yield, fruit quality and Angular Leaf Spot Disease

Endophytic bacteria (EB) are ubiquitous in most plant species and they colonize plant tissues actively and systemically. Their colonization and persistence in the plant may be crucial to plant growth, yield and suppressing diseases. In this study, the long-term population dynamics of the two EB, namely Ochrobactrum spp. strain CB36/1 and Pantoea agglomerans strain CC37/2 in cucumber plants (Cucumis sativus L. cv. Gordion F1), were monitored. Also, the potential effects of these EB on plant growth, fruit quality, and yield, as well as the influences on Angular leaf spot disease of cucumber (ALS) and the yield under the disease pressure, were investigated. Plants were grown using the soilless cultivation technique in the greenhouse. Inoculation of the EB took place twice, and their population in plant tissues were monitored periodically for 62 days. Both EB isolates survived in plant organs until the end of the growing season, but over time, population densities dropped from 10(5) to 10(3) CFU g. plant 1 with the age of the plant. The EB applications had significant effects on fruit length, color and firmness. Total yield increased by 22% with CB36/1 and 21% with CC37/2 without disease pressure. Only CC37 / 2 significantly reduced the severity of ALS disease by 41% and increased yield by 22% compared to pathogen treatment alone. In this study, it was observed that the EB strain CC37/2 might contribute to reducing the chemical input and prevent the yield losses in soilless growing systems within the integrated agricultural concept.