Watermelon breeding

does not appear. First page follows. Introduction Although the watermelon, Citrullus vulgaris Schrad., has been cultivated in America since 1629(9) and in Africa for over 4,000 years,(7) relatively little attention has been given to the effects of inbreeding, to environmental factors affecting fruit setting, or to measured varietal improvement through modern breeding methods. The effects of inbreeding assume economic importance because many watermelon varieties, normally subject to extensive cross-pollination, are apparently heterozygous as to many characters, particularly those affecting plant vigor; size, shape, and color of fruit; color and texture of flesh; sugar content; and certain seed characters. Doubtless the most important improvement needed in watermelons is the development of strains resistant to the wilt disease, caused by Fusarium niveum E. F. S. Wilt is now a factor limiting production in the Sacramento, San Fernando, and San Joaquín valleys of California and in many other states. As the fungus is well established in the southern states, growers have some difficulty in locating disease-free soil. A single crop of watermelons often contaminates the soil to the extent that all subsequent crops may be seriously infected. Eventually, therefore, all the watermelon districts, each demanding a particular type of fruit, will probably need wilt-resistant strains. As inbreeding must continue for several generations in order to establish homozygous wilt-resistant strains, workers evidently must (a) measure the effect of such inbreeding, (b) establish the mode of inheritance, (c) develop pollination technique, and (d) determine the occurrence of self-sterility.