Abstract
The study was conducted to screen local and improved bean varieties for resistance to halo blight disease caused by Pseudomonas syringae pv. phaseolicola. A total of eight improved (Sokoine University of Agriculture (SUA) 90, Rojo, Zawadi, Mshindi) and local (Mwasipenjele, Masusu, Kabhaya, Mabula) bean varieties were collected from breeders at SUA and farmers at Ileje district in Songwe region. Isolation of P. syringae pv phaseolicola from bean seeds was conducted using Liquid Assay method. Results indicated that, bacterial isolate L1 from local bean variety Mwikala produced similar characteristics as those obtained from reference strain of P. syringae pv phaseolicola in the biochemical and pathogenicity tests on host plants. Using bacterial isolate L1, there was significance difference (P < 0.05) on incidence and severity of halo blight disease. The highest disease incidence had (89%) was on local bean variety Mabula, while the lowest had (67%) was on improved varieties Zawadi and Mshindi. Disease severity of improved varieties zawadi and mshindi when compared with other varieties were at low severity (disease score 4). It was concluded that the Zawadi and Mshindi were less susceptible to halo blight disease. This study needs to be repeated if same results were obtained aside these two improved varieties (Zawadi and Mshindi) of bean which could be recommended to farmers. Key words: Assay, incidence, inoculum, isolate, Pseudomonas syringae pv. phaseolicola, disease severity.
Highlights
Common bean (Phaseolus vulgaris L.) is an important leguminous crop and native to America (Gepts and Dpbouk, 1991)
The results for purity analysis indicated that bean seed sample number 3 variety Rojo collected from SUA had the highest (99.98%) proportion of pure seed followed by sample number 2 (99.97%), 1 (99.93%), 6 (99.90%), 4 (99.89%), 7 (99.67%), and 5 (99.16%) (Table 1)
The results showed that the moisture content determined using lower constant temperature oven method of bean seed samples ranged from 10 to 14.5% (Table 1)
Summary
Common bean (Phaseolus vulgaris L.) is an important leguminous crop and native to America (Gepts and Dpbouk, 1991). It is an important source of minerals, protein content (~22%) and vitamins for many developing countries where they cannot afford meat (Moraghan and Grafton, 2001; Hillocks et al, 2006; Graham et al, 2007;). The major producers of common bean worldwide are Brazil, Mexico, United State, Ethiopia, Turkey, Indonesia, Tanzania, Uganda and Angola (Beebe et al, 2013). In Africa, bean production is concentrated in densely populated Eastern and Southern Highlands of the continent (Beebe et al, 2000). In Tanzania, bean is grown in cool regions, the Southern Highlands (Iringa, Songwe, Mbeya, Rukwa, Katavi, Njombe and Ruvuma regions), Northern Highlands (Arusha, Tanga, Kilimanjaro and Manyara), Western Highlands (Kagera and Kigoma)
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