Author : A Amsalu
Year : 2007
A total of 50 rhizobial isolates of field pea (pisum sativum) were collected from central Shewa, Gojam, Gondar, Wollo, Tigray, Arisi, Bale, Harar and Walayta. The rhizobia were isolated in culture and characterized using cultural, colony morphology and physiological characteristics. All isolates except three, changed bromothymole blue indicator to yellow indicating they are acid producers and fast growing and 84% of the isolates were fast growing and 16% were slow growing. The isolates showed diverse characteristics in their carbohydrate utilization, intrinsic antibiotic and heavy metal resistance. Most isolates from Harar and Arisi-Bale were found to be more tolerant to higher NaC1 concentration, pH (4.5 and greater than or equal to 9) and temperature (5 and greater than or equal to 38 C deg) extremes than others. Dendrogram obtained through cluster analysis using NT-STS version 2.1 in 62 phenotypic characteristics showed that isolates can be grouped into different clusters and groups. The relative symbiotic effectiveness of the isolates was determined in sand culture and analysis of plant dry matter, nodule number and total nitrogen uptake data using SPSS 11.5 at p=0.05 showed a significant difference among isolates. The highest dry matter of 3.35 g/plt was accumulated by each of the inoculant isolates of NSRIFP1 (Shewa) and NSR1FP5 (Gojjam) that were significantly different from the N-fertilized control, followed by NSR1FP2 and NSR1FP4 (Gojjam) that accumulated 2.91 g/plt and 2.60 g/plt, respectively. The percentage of total nitrogen (TN) per plants were ranging from 1.19 for isolate NSR1FP28 (Arisi-Bale), being the lowest, to 2.93 for each of isolates NSR1FP1 (Shewa) and 2 (Gojjam), being the highest. Most isolates from Tigray (86%), Shewa (80%), Gojjam (71%) and 67% of Gondar-Wollo were effective and very effective whereas, higher percentage of lowly effective and ineffective isolates were found from Harar and Arisi-Bale. The most effective isolates were NSR1FP 1 (Shewa) and 5 (Gojjam) with 133% dry matter accumulation relative to N- fertilized control and total nitrogen percentage (TN) of 2.93 and 2.88. The least effective isolate was NSR1FP47 (Harar) with 23% dry matter accumulation and 1.55 TN. In general, isolates were very diverse in many of laboratory and greenhouse tests. Hence, for better understanding of isolates to their interaction with host plant, further physiological, molecular and field studies are recommended.