Genetic control of irregular striping, a new phenotype in Cucurbita pepo

Longitudinal striping of the fruit exterior is a common trait in Cucurbita pepo (pumpkin, squash, gourd). Striping occurs as ten pairs of alternating dark and light stripes that are regularly situated in accordance with the ten sub-epidermal carpellary vein tracts. Usually, the dark stripes occur in the central areas between the vein tracts, with the light stripes occupying the remainder of the fruit surface. A new phenotype is described in which dark spots or streaks occur in the central areas between the vein tracts; these are usually accompanied by dark streaks or stripes that occur adjacent to and over part or all of the length of some or all of the ten carpellary vein tracts. The inheritance of this irregular striping pattern was studied by crossing an accession that bred true for this phenotype with a near-isogenic line having light-colored fruits. The results indicated that irregular striping is dominant to light coloration and is conferred by a single gene. Testcrosses for allelism with regular striping were prepared by crossing the irregularly striped accession with near-isogenic lines having broad stripes, l-1BSt/ l-1BSt, and narrow stripes, l-1St/ l-1St. The testcross results revealed that irregular striping is conferred by an allele at the l-1 locus, designated l-1iSt. The l-1iSt allele is dominant to light-colored (l-1), recessive to dark-colored (L-1), and can be co-dominant or recessive to broadstriped ( l-1BSt) and narrow-striped ( l-1St), depending on whether or not it is fully expressed. Dominance relationships at the l-1 locus can, therefore, be represented as L-1 > (l-1BSt > l-1St) >= l-1iSt > l-1.