Sunflower (Helianthus annuus L.) is the fourth most important oil crop in the world. The growing of sunflower is, however, faced with challenges of infestation by disease and infection by pests. Farmers rely heavily on use of broad spectrum pesticides to combat diseases, implying high pesticide bills that sometimes make sunflower farming economically not feasible. It, therefore, becomes imperative to identify varieties that have natural resistance to pathogen infection. Sclerotinia diseases are among the most deleterious diseases of sunflower globally. Oxalic acid is the pathogenicity factor for species such as Sclerotinia sclerotiorum. While oxalate oxidase has been shown to confer some resistance to oxalic acid degradation in a number of other oil crop, it is hypothesized that the same can successfully apply for sunflower. This book, therefore, presents a case study where different sunflower varieties are analyzed for their resistance to oxalic acid degradation as well as their oil yield and quality. Identification of resistant and high yielding varieties should go a long way in promotion of economically feasible sunflower farming by stakeholders in the edible-oil industry.