Cucurbit Genetics Cooperative Report 7:88 (article 39) 1984
Weeden, N.F.
Dept. Horticultural Sciences, New York State Agricultural Experiment Station, Geneva, NY 14456
At least two forms of fructose 1,6-diphosphate aldolase (EC 4.1.2.13) are present in leaves of Cucurbita species. One of these isozymes is localized in the plastid compartment while the other is cytosolic (1). Polymorphism in the plastid-specific aldolase has been observed using electrophoretic techniques. The genetic basis of this polymorphism was investigated in the backcross C. maxima x (C. maxima x C. ecuadorensis) and in backcross and F2 populations of a cross involving the two C. pepo cultivars ‘Black Jack’ and ‘Early Prolific Straightneck’. In all cases the aldolase phenotype segregated as if controlled by a single locus with codominant alleles (Table 1). The locus has been designated Aldo-p, the suffix reflecting the intracellular compartmentation of aldolase.
As is typical for allelic variants of isozymes, ‘wild type’ and ‘mutant’ terminology is not appropriate. Both allozymes perform the identical biochemical catalysis, and it would be very difficult to demonstrate which allozyme was derived from which. I have used the term “fast” and “slow” to discriminate between the two allozymes segregating in each population. It should not be assumed that the slow allozyme in the C. maxima x (C. maxima x C. ecuadorensis) backcross is the same as the slow allozyme in the C. pepo populations; instead, 4 Aldo-p alleles have probably been identified: 2 in C. pepo, a third in C. maxima and a fourth in C. ecuadorensis.
Table 1. Number of individuals with designated aldolase phenotypes in three segregating populations.
| Population | Aldolase phenotype | ||||
|---|---|---|---|---|---|
| n | slow | slow/fast | fast | x2 | |
| C. maxima x (C. maxima x C. ecuadorensis) | 45 | 21 | 24 | – | 0.20 |
| Black Jack x Early Prolific Straightneck (F2) | 54 | 15 | 26 | 13 | 0.22 |
| Black Jack x (Black Jack x EPSN) | 20 | 10 | 10 | – | 0.00 |
Literature Cited
- Anderson, L.E. and V.R. Advani. 1970. Chloroplast and cytoplasmic enzymes. Plant Physiol. 45:585.