Citrus Polymethoxylated Flavones Can Confer Resistance against Phytophthora citrophthora, Penicillium digitatum, and Geotrichum Species

The polymethoxylated flavones observed in the essential oils of the byproducts of various Citrus fruits after industrial processing were as follows: sinensetin, nobiletin, and heptamethoxyflavone in clementine; sinensetin, quercetogetin, nobiletin, heptamethoxyflavone, and tangeretin in sour orange and sweet orange. Penicillium digitatum was totally inhibited (100%) by application of the polymethoxylated flavones present in the extracts from the clementine and sweet orange oils and 77% inhibited by those extracted from the sour orange oil. Phytophthora citrophthora was 100% inhibited by sour orange oil, 72% by clementine oil, and only 14% by sweet orange oil. Geotrichum sp. was more sensitive to the sour orange extract, being inhibited by ∼57%, whereas clementine and sweet orange produced inhibition rates of 47 and 34%, respectively.