Studies on the bean (phaseolus vulgaris l.) Rust disease caused by uromyces phaseoli (reben) wint.

Field studies of the bean (Paaseolus vulgaris) rust disease caused by Urocnyces phaseoli were carried out at Ritengano Tukuyu, Jyole they and Morogoro University farr\s. International Bean Rust Nurseries (I3Ks) were set at the three experimental sites while screening for rust disease resistance among sane local bean varieties was carried out at Uyole, Mbeya and Morogoro. Trial varieties ware planted in single rows and the plots were replicated twice. Disease readings were done at flowering and pod filling stages. Assessment of disease incidence of anthracnose causcd by the fungus Colletorichjm lindemathianum, angular leaf spot caused by Isariopsis griseola bacterial blights and viral infections, were carried out on the trial varieties IBRN studies indicated a large potential of -nultinlo disease resistance and variability of the rust pathogen. The local variety TMO 31 had the highest resistance to rust in all the test areas while varieties TMO 25, TMO 40, TI1C 5S# TMO 66 and TMO 67 were resistant in two tests and was intermediate in the 3rd test. Varieties TMO 33, TMO 52, TMO 79, TMO 105 and TMO 91, TMO 93, TMO 95, THO 105 and TMO 126 were resistant in one test and had intermediate reaction in the other two tests. All these varieties were considered to be good sources of resistance in that they did not have any susceptible reaction in the three field evaluation. The following varieties seemed promising in terms of multiple disease resistance, TMO 25 (unknown), TMO 33 (Kankasherere) , TMO 40 (Kashukari) , TMO 59 (Unknown) ,TMO 62 (Kashoro) , and TMO 64 (Xyabakila) . Laboratory culture of uredospores of U. phaseoli was attempted in the Botany Laboratory, University of Dar es Salaam. Disease incidence occurred when bean plants with half expanded leaves were inoculated and incubated for 2 4 hours in a cooled chamber (19°C). No disease synptcms were observed on plants incubated at room temperature (25 C). The morphology and anatomy of spores (urodospores and teliosoores) and diseased leaves respectively were studied. Uredospores were observed to be brown, round and shaped like a doughnut while teliospores were dark brown, oblong anl stalked. Microtome sectioning revealed that the fungus distorts the anatomy of a bean leaf.