Participatory Potato (Solanum tuberosum L.) Bacterial Wilt (Ralstoniasolanacearum (E.F.Smith.)) Management in the Central Highlands of Ethiopia

In the major potato growing areas of the central highlands of Ethiopia, experiments on Effective microorganism (EM), Bio-agents as soil amendment, seed cycle and crop rotation using farmers’ field school (FFS) approach was conducted between 2009 and 2014. In the soil amendment activity the treatments were improved management package (full fertilizer rate, recommended spacing and improved variety (Jalene); soil amended with full rate of EM-fortified compost+improved management; Soil amended with 1⁄2 EMfortified compost and 1⁄2 fertilizer of the recommended rate for the area+improved management packages; Soil amended with 1⁄2 EM fortified compost and 1⁄2 fertilizer of the recommended rate for the area + 1⁄2 EM spray on the foliage weekly+improved management packages; seed tube treated/socked in EM at a dilution of 1:1000v/vl for 30 minutes and farmers practice (1/2 of the recommended fertilizer to the area using local variety). In the rotation trial, one-season rotation and two-season rotation experiments were conducted on fields which had medium infection. In the seed cycle experiment, three improved potato varieties namely: Jalene (CIP-384321.19), Guden (CIP-386423.13) and Awash (CIP-378501.3) and two local varieties, ‘Nechabeba’ and ‘Agazer’ were tested for four consecutive years. In the soil amended with EM fortified compost experiment, improved variety had the lowest 21% and 47% mean disease incidence and percent latent infection compared to the local variety which had 25% and 53% respectively. Plots amended with 1⁄2 EM-fortified compost, 1⁄2 fertilizer of the recommended rate for the area and 1⁄2 EM spray had the lowest percentage of latently infected tubers, 26.7% and 30.0%, on the improved and local variety respectively compared to the control which had 50.0% and 76.8% but the incidence of the disease was not statically significant. In the seed cycle experiment, in the 1st season, the local variety had significantly (p<0.05) higher 20.93% BW incidence than the improved variety which had 3.98% whereas in the 4th cycle it increased by 75% and 50% respectively. Under wear potato production scenario, in the 1st cycle, the yield loss was estimated to 4 and 7% in improved and local varieties but in the 4th cycle it has been increased to 21% and 32% respectively. If the produce is for seed purpose, then the estimated loss was increased from 5.34% to 28.6% and from 20.78 to 67.34% from the 1st to the 4th on improved and local varieties respectively. A One season rotation of potato with cabbage, beans, and carrot significantly (P<0.05) reduced the incidence of the disease and had 15.4, 22.1 and 27.3% respectively compared to 45.2% in the control and resulted in negative and significant, Y= -0.2588x +29.767 (R2=0.7946) and Y= -0.177x+28.019 (R2=0.4597), correlation of mean tuber yield over disease incidence. Similarly, the two-season rotation had significant (p<0.05) negative correlation Y=-0.177x+28.019 (R2=0.4597) tuber yield over disease incidence and significantly (P<0.05) increased marketable tuber yield compared to the mono crop potato. The result of these research activities suggested that FFS through session supported extension approach was found to be effective to generate and disseminate bacterial wilt management technologies. Soil amendment with fortified compost helped to reduce the incidence of the disease. Sources of seed and seed revolving year after year was found to be the major factor for high tuber yield loss and the main path for the dissemination of the causative agent of wilt. One and two season rotation with beans and cabbage reduced wilt incidence, latent infection in tubers and increased tuber yield.