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Cucurbit Genetics Cooperative Report 5:8-9 (article 4) 1982

The Genetic Regulation of Several Seed Traits in Compact (cp cp) Cucumbers - Maternal vs. Embryonic Control

M. D. Edwards and R. L. Lower

University of Wisconsin, Madison, WI 53706

Seed quality is a major limitation to utilization of the compact plant-type in cucumbers (1). Alterations in seed weight and shape are associated with poor emergence and are apparently pleiotropic effects of the gene conditioning compact plant type, cp (2). Although the compact allele exerts a major influence on seed quality, seed production environments and quantitative genetic effects condition substantial variability for seed traits within compact populations (3).

A heterogenous population of compact cucumber genotypes was established in the summer of 1980. Plants were spaced about 15 cm apart in rows with 90 cm spacings between rows. Thirty-eight sets of reciprocal crosses were obtained by hand-pollinations in the field. Natural outcrossing was prevented by covering flowers with halves of size 000 gelatin capsules. Fruit were harvested and all extracted seeds were subjected to two days fermentation at 20±2°C and two reps at 25±1°C. Pots were watered with distilled water and emergence percentage was recorded after 14 days.

Analysis of variance was conducted using a completely random effects model. Temperatures were a significant source of variation for emergence percentage but all interactions with temperature were non-significant. Mean emergence percentages for 20°C and 25°C were 43% ad 51% respectively.

Temperatures were pooled into block effects to produce a simplified analysis of variance which is presented in Table 1. Maternal parents nested within crosses were a significant source of variation for emergence percentage, seed weight and percent normal seeds. Crosses were a non-significant source of variation for all traits. Components of variance attributable to cross effects and maternal parents nested within crosses were also isolated from mean squares values. Zero values were obtained for variance due to cross effects for the traits of emergence percentage and percent normal seeds. A positive estimate was obtained for seed weight, but the estimate was one-tenth the magnitude of the corresponding variance due to maternal parents nested within crosses.

These results emphasize the importance of broad-sense maternal effects in the regulation of the seed traits evaluated in this study. Nuclear genetic effects did not contribute significantly to any of the traits studied. The maternal effects observed may be attributable to any of several influences, including: 1) cytoplasmic effects, 2) maternal genetic effects, or 3) environmental effects. If due to cytoplasmic influences, these effects should be passed from mothers to progeny with undiminished magnitude. In the absence of cytoplasmic effects, heritabilities may be used to assess the relative contributions of maternal genetic effects and environmental effects. Further studies are planned to determine the nature of the maternal influence on emergence percentage and related seed traits.

Table 1. Analysis of variance for seed traits.

 

 

Mean square

Source

df

Emergence percentage

Seed weight

Percent normal seeds

Block

3

3850 **

0.003 NS

144 NS

Cross

37

3286 NS

0.30 NS

886 NS

Maternal parent (Cross)

38

4506 **

0.25 **

1464 **

Error

225

556

0.005

150

** Significant at 1% level

Literature Cited

  1. Edwards, M. D. and R. L. Lower. 1980. An analysis of factors related to germinability of seed from compact cucumber plants (Abst.).
  2. Edwards, M. D. and R. L. Lower. 1981. Investigations into the characteristics of seed from compact cucumber plants. Cucurbit Genetics Cooperative 4:2-4.
  3. Edwards, M. D. and R. L. Lower. 1981. Selection against a seed abnormality in compact cucumber plants (Abst.). HortScience 16:35.
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Page citation: Wehner, T.C., Cucurbit Genetics Cooperative;
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send questions to T.C. Wehner; last revised on 23 October, 2009