T219H and Tl35, two of the more vigorous chlorophyll-deficient types in the Genetic Type Collection, both have distinctly light green foliage through-out their life cycle. They are controlled by different genes since the Tl35 phenotype is caused by a homozygote, y9y9 (Probst, 1950), and the T219H phenotype by a heterozygote, Y11Y11 (Y11Y11 has a bright orange-yellow seedling-lethal phenotype) (Weber and Weiss, 1959). However, because of the similar phenotypes, it has been suggested that y9 and y11 may be multiple alleles at the same locus.