The present investigation was carried out during the two summer seasons of 2015 and 2016 at sharnoob vilage,
Damanhur city, Behera governorate, Egypt, to study the effect of foliar application of yeast extract , hydrogen peroxide
(H2O2) and combination of them on growth, yield and quality of sweet potato tuberous roots, using two sweet potato
cultivars, Abees and Mabrouka. Generally, the results indicated that Abees cv. recorded maximum values of number of
shoots/ plant in the second season, plant length in the first season , foliage fresh weigh/ plant, total sugar %, reducing
sugar %, carotene %, dry matter % and starch% contents of roots. Results showed also that spraying of yeast extract gave
the highest means values for all studied traits of vegetative characters of two cultivars; in both seasons. Moreover,
spraying of yeast extract gave the highest significant means values for total yield of roots/plant, weight of marketable
roots/plant, number of marketable roots/plant, total sugar %, reducing sugar %, carotene %,dry matter of roots % and
starch% contents in roots compared with other treatments in both seasons. The treatment combination of growing Abees
cultivar and yeast extract recorded the highest mean values of the most studied characters compared with other treatments.