CHEMICAL RELATIONSHIP BETWEEN SCION AND STOCK IN CITRUS

It is commonly known that Citrus varieties are propagated commercially by budding. The most important varieties grown in California are Washington Navel orange and Valencia orange (Citrus sinensis Osbeck), Marsh grapefruit (Citrus maxima Merrill), and Eureka and Lisbon lemon (Citrus limonia Osbeck). The rootstocks upon which these varieties are budded are sweet orange (Citrus sinensis Osbeck), sour orange (Citrus aurantium L.), grapefruit (Citrus maxima Merrill), and to a small extent rough lemon (Citrus limonia) and trifoliate orange (Poncirus trifoliata Raf.). The degree of congeniality shown between scion and rootstock in Citrus has been reported by Webber (7), Newman (6), and others. Their observations show in a general way that the lemon scion overgrows the sour rootstock as is indicated by a bulge just above the bud union, and overgrows the sweet stock to a less extent, whereas the opposite effect is seen when the lemon is budded on grapefruit or trifoliate orange, in which case the trunk of the rootstock is larger than the lemon trunk. Similar but less pronounced size differences exist when the Navel or Valencia orange or the Marsh grapefruit is budded on sour, sweet or trifoliate rootstocks. On the other hand a smooth bud union results when these standard