Genetic characterization and molecular mapping of a chlorophyll deficiency gene in sunflower (Helianthus annuus)

A major gene controlling chlorophyll deficiency (phenotyped by yellow leaf color, yl) in sunflower was identified and mapped in an F2 population derived from a cross between two breeding lines. Greenness degree was scored by a hand-held chlorophyll meter in the F2 population. Leaf tissue from the parents, F1 hybrids, and some F2 progenies were also sampled to determine the chlorophyll content. All F1 plants had normal green leaf color and the segregation of the plants in the F2 population fits the monogenic ratio (χ(3:1)2=0.03, p>0.9), indicating that leaf color is a monogenic trait with normal green dominant over yellow leaf color in this population. The contents of chlorophyll a, chlorophyll b, and total chlorophyll in the yellow-leafed lines were reduced by 41.6%, 53.5%, and 44.3%, respectively, in comparison with those in the green-leafed lines. Genetic mapping with molecular markers positioned the gene, yl, to linkage group 10 of sunflower. An SSR marker, ORS 595, cosegregated with yl, and a TRAP marker, B26P17ga5-300, was linked to yl with a genetic distance of 4.2 cM. The molecular marker tightly linked to the chlorophyll deficiency gene will provide insight into the process of chlorophyll metabolism in sunflower.