Genetic studies on the leaf variegation of Allium cepa L.

Abstract

Only one plant of onion having yellow-green stripes on leaves was found under field conditions in 1960. Because of male sterility, it was propagated vegetatively to maintain the clonal line. Fortunately, male-fertile variegated plants were found out of those male-sterile clones in 1965. The variegated leaves were striped alternately with green and yellow bands. The width of the stripes varied considerably as shown in Fig. 1. These male-fertile variegated plants were used as materials in the present experiments to clear up the genetic behavior.
The results of self-pollination in the variegated plants are shown in Table 1. When self-pollinated the variegated plant produced green and yellowish white seedlings. The yellowish white seedlings perished immediately after germination. The variegated plants were distinguished from the green plants during the late stage of growth. The green plants obtained from the original variegated plants by vegetative propagation bred true for green in the first generation of selfing (Table 1).
The results of the reciprocal crosses between variegated and normal green plants are shown in Table 2. The F₁ generation from the cross variegated plant _??_×normal green plant _??_ segregated green and yellowish white in seedling stage, and green and variegated in adult stage.
The self-pollinated green F₁ plants bred true for green in F₂. The variegated F₁ plants produced green, yellowish white, and variegated plants in the F₂ and F₃ generations.
The F₁ plants of the cross normal green plants _??_×variegated plant _??_ were green, which produced only green plants with the exception of a single variegated plant in the F₂ generation.
From these results the leaf variegation of onion seems to be maternally inherited, and controlled by plastogenes.
A genetical mechanism is not known by which the male-fertile variegated plants were induced from the male-sterile ones. It would be due to somatic segregation during vegetative propagation (Smsms→SMsms, cf. JONES and CLARKE, 1943).
The genetic interrelation between male sterility and variegation requires further study.