PHENOTYPIC AND GENETIC DIVERSITY OF NATIVE RHIZOBIUM ISOLATED FROM ROOT NODULES OF LEGUMINOUS PLANTS GROWN IN RECLAIMED SOIL, EGYPT

Abstract

An investigation of the phenotypic characteristics of 19 rhizobial strains, isolated from root nodules of different plant legumes grown in the soil of agriculture farms in Ismailia governorate, transpired. Most isolates were creamy or white opaque, mucoid, with a convex elevation, translucent, and smooth margined. Microscopic investigation revealed that all bacterial isolates were rod-shaped and had no positive affinity for Gram-stain. Identifying rhizobial cultures from any bacterial contaminants employed confirmatory tests based on prepared special media, including YMA supplement with Congo red, glucose peptone agar, Kit-lactose agar, and Hoffer’s alkaline test. Based on an infectivity test, all isolates proved their ability to reinfect their host. These rhizobial isolates, classified into two categories, included fast and slow-growing rhizobia according to their growth in the YEM medium containing bromothymol blue (BTB). Meanwhile, the assessment of the genetic diversity among these isolates proceeded using ISSR and RAPD markers, which ISSR marker proved a more powerful tool in discriminating among the tested isolates than the RAPD marker. The cluster analysis, with the RAPD marker, classified the isolates into two main groups. The first group included the isolates (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 13), while the second group contained the isolates (12, 14, 15, 16, 17, 18, and 19). Moreover, using ISSR markers also showed a cluster of two main groups with diverse categories; the first cluster included isolates 1 to 11, and the second group contained isolates 12 to 19.