ABSTRACT:Bet a (β) -alanine is a natur ally occ urring nonproteing enic ami no acid . β-alanine suppressed t he growt h activities of s ugar beet pathogens R hizoc tonia sol ani K uhn (A G2-2), Sclerotium rolfsii S acc. and F usarium s olani (Mart) S acc.w hen applied t o t he growt h medium at diff erent concentr ations (12.5 -100 µg/ ml). W hen ap plied to soil, β-alanine suppressed f ungal inf ecti on of tw o s ugar beet cultivars Ras poly and TO P. In abs enc e of β -alanine, R. s olani w as t he m ost virul ent agains t c vs. Ras poy and TO P. Vir ulence w as directly c orrel ated wit h t he ac tivities of cell wall-degrading enz ym es produc ed by thes e pathogens in viv o. R educ ed virulenc e of R . solani, S. rolf sii and F . s olani under β-alanine stress was due t o d ecreas ed inocul um potential of the pathogens as res ult of the reduction of t he c ell wall -degrading enz ymes . Growt h par amet ers i ncluding emergence, plant length and dry weight of s ugar beet were signific antl y i ncreased at all inv estigated β-alanine c oncentr ations. T he infection rat e was signific antl y d ecreased with incr easi ng β -alanine stress , w hereas the t ot al s ugar reducing val ues (TRV) was signific antl y increased in t he tes ted sug ar beet c ultiv ars. The res ults indicated the p ossibility of the test ed amino acid for protecti on of s ugar beet plant c ultiv ars ag ainst f ungal inf ecti on. KEY WORDS:Sugar beet pathogens, β -alanine, growth activiti es, c ell w all -degrading enz ym es, sug ar cont ents. CORRESP ONDENCE:Mo ham ed E w ei s Department of Botany and Microbiol ogy, Facul t y of Sci ence, Cairo U niv ersit y,