Variation for Yield within Locations in Homogeneous and Heterogeneous Cucumber Populations

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Cucurbit Genetics Cooperative Report 7:33-34 (article 15) 1984

Todd C. Wehner
Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695-7609

Environmental variation is an important source of error in evaluating yield of lines in small-plot trials. Smith et al. (2) found a large effect of environment for yield (fruit number per plot) in once-over harvested plots, and measured the narrow-sense heritability to be only 0.17. Environmental variation can be overcome by use of multiple years, locations and replications for yield trials. However, limited seed supplies and the large numbers of families to be evaluated in the early stages of a breeding program preclude the use of multiple test environments. The objective of this study was to determine the variability of unreplicated plots of genetically homogeneous or heterogeneous populations.

Methods. The pickling cucumber ‘Calypso’, without pollinator, and the diverse pickling cucumber population, NCMBP, were used as the homogeneous and heterogeneous populations, respectively. NCMBP is the North Carolina Medium Base Pickle population, which was developed by intercrossing most of the known pickling cucumber cultivars and lines in isolation for 3 years. The populations were planted on raised, shaped beds with 0.5 m tops and 1.5 m apart (center to center). The plots were 1.5 m long, and were planted on May 23, at the Horticultural Crops Research Station near Clinton, NC. The plots were overplanted and thinned to 15 plants at the first true leaf stage. Plots were harvested when most had 10% oversize (>50mm diameter) fruit in them, and the number of fruit per plot counted. Yield data were considered missing in plots where the plant stand was at all questionable.

Results. The homogeneous pickling cucumber population made up of the hybrid cultivar, ‘Calypso’, had yields that varied from 9 to 35 fruit per plot in 150 plots measured (Table 1). The variation for yield among plots of ‘Calypso’ is all caused by environmental effects. The heterogeneous population, NCMBP, had a greater range for yield than ‘Calypso’, with 10 to 56 fruit per plot in the 153 plots sampled (Table 2). However, using the data from the plots of ‘Calypso’, 56% of that range could be accounted for by environmental effects. Thus, it is important to recognize the strong effect the environment has on yield of small plots and to take steps to account for that variability. Replication, correction of plot yield using neighboring plots, or subdivision of the field into smaller units for selection as done by Gardner (1) are approaches that should be considered to help solve the problem of environmental variation within yield trials. while this information has been known for some time, it is more convincing when demonstrated directly as in Tables 1 and 2.

Table 1. Total fruit per plot in 25 tiers of 6 rows of ‘Calypso’.z

Field tier

 Field row
3 4 12 13 21 22
1 24 23 21 35 15 24
2 29 24 25 25 27 19
3 20 26 24 26 27 25
4 23 24 29 31 25 25
5 12 28 23 27 28 26
6 24 24 30 22 29 30
7 25 24 – 20 24 24
8 24 27 21 28 28 21
9 28 24 – 27 30 26
10 35 32 25 23 27 22
11 16 24 28 30 30 24
12 27 28 24 31 24 21
13 24 28 – – 24 28
14 24 25 – 25 23 29
15 28 21 26 29 27 20
16 21 26 – 21 21 25
17 21 25 21 24 30 26
18 22 25 20 – – 24
19 21 28 28 – 24 28
20 20 26 28 27 28 22
21 25 25 22 23 15 20
22 16 21 29 – 22 20
23 21 24 30 22 22 24
24 11 18 30 28 22 30
25 9 18 25 28 – 19
Mean 25  
Standard deviation 4  
Range 9-35  
z Plots (1.5 m long) harvested at 10% oversize.

Table 2. Total fruit per plot in 17 tiers of 9 rows of the North Carolina Medium Base Pickle Population.z

Field tier

 Field row
1 2 3 4 5 6 7 8 9
1 33 37 26 48 27 35 40 43 28
2 36 32 36 41 27 28 25 10 23
3 43 40 38 32 32 33 44 36 35
4 25 47 40 56 38 27 40 35 34
5 28 43 33 40 39 33 51 32 28
6 45 37 31 40 39 12 41 23 39
7 44 44 41 42 42 37 49 35 41
8 38 45 46 53 33 29 38 42 37
9 38 29 40 43 48 16 38 33 42
10 39 44 52 46 40 27 30 50 43
11 31 34 35 21 40 39 33 45 39
12 45 31 34 44 35 26 33 43 45
13 41 34 45 46 34 24 27 45 38
14 39 22 31 48 37 21 40 37 36
15 35 37 26 56 52 25 46 38 45
16 25 47 36 46 38 23 56 38 37
17 36 34 27 43 32 28 39 43 27
Mean 37  
Standard deviation 8  
Range 10-56  
z Plots (1.5 m long) harvested at 10% oversize

Literature Cited

  1. Gardner, C.O. 1961. An evaluation of effects of mass selection and seed irradiation with thermal neutrons on yield of corn. Crop Sci. 1:241-245.
  2. Smith, O.S., R.L. Lower and R.H. Moll. 1978. Estimates of heritabilities and variance components in pickling cucumber. J. Amer. Soc. Hort. Sci. 103:222-225.