Seedling Mutants in C. maxima

This is a good place to introduce the concept of genetic markers. Some day it might be known that an important trait in giant pumpkins is located on the same chromosome as a harmless mutation. Then one could look at the seedlings, perhaps by a biochemical assay, and discard the useless plants. More about that below.

Seedling mutants are prized by teachers because it is easy to grow seedlings in the classroom to demonstrate genetic principles. Each pupil can be given one or more seeds to plant in a paper cup or half pint milk carton. Kids love planting seeds and watching them grow. I found seeds to be one of the most interesting projects for kids in all years of K-12. Besides the genetics lesson, kids learn lots when growing seedlings. If you are not familar with genetics look at page pk010.htm.

Known Seedling Mutants in C. maxima

Yellow seedling has the symbol ys. The seedlings are yellow and can't make food because they have some unknown defect in photosynthesis. In various plants many types of mutants are known which result in white, yellow, striped, or pale plants. Perhaps you will see one in your garden.

Light green young leaves has the symbol v. This recessive mutation is not lethal because older leaves have normal color and photosynthetic ability. I do not know whether this mutation is visible in all leaves when young or just the early leaves.

The above two recessive mutations are the only visible mutations that I know about in C. maxima seedlings.

Please Report any Unusual Seedlings.

Please report any unusual seedlings you find in your garden. If the mutant is lethal (dies), we can recover it from other seeds from the same fruit. It can be maintained by selfing or sibbing. However recessive mutants will appear only selfed fruit or matings of this type: Mm x Mm.

Enzyme Mutations in Seedlings

133 Rivard 1998 Lobed Cotyledons Deformity

Subject: Polycotyledons in 133 Rivard Date: Sat, 24 Apr 1999 22:42:07 -0700 From: "Harold Eddleman Ph.D." <indbio@disknet.com> Organization: Indiana Biolab To: genetics@onelist.com

Dear Rock and Genetics I planted 6 seeds of 133 Rivard 1998 7 days ago and 4 came up in 3 and 4 days at mostly 75 to 85 F. Two seeds have only swelled. I will take them to lab and dissect. Of those which came up, none has perfect cotyledons. One has 4 seed leaves. Actually on close examination, it has 2 but each is divided into two with a midrib in each. Another is younger and difficult to decipher. It appears to have one seed leaf divided into 3 lobes. Since cotyledons are formed during early embryogenesis inside the fruit, conditions of germination should have no effect on the above deformities and the leaves were folded inside the seed. The numbers do not seem to fit any common mendelian ratio, but the numbers were low. Rock, it would be nice to try to pool my data with yours some weeks in the future when more seeds have been germinated. The only genetic ratio we would expect is 3:1 or 2:1 if the 2 seeds which di not germinate are a lethal form (the double recessive). 1 : 2 : 1 is the genotypic ratio 2 : 2 : 2 is the ratio I observed: 2 dead : 2 funny leaves : 2 normal It is possible we have a genetic mutation here. If it is mutant, when I plant the normal and deformed separately, and germinate the seeds produced. I should seed different results. -- Harold Eddleman Ph.D. Microbiologist. mailto:indbio@disknet.com Location: Palmyra IN USA; 36 kilometers west of Louisville, Kentucky http://www.disknet.com/indiana_biolab/pk704.htm <= seed mutants

To be continued

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