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Cucurbit Genetics Cooperative Report 6:38-39 (article 18) 1983

Effect of Unequal Competition from Bordering Rows on Pickling Cucumber Yield Trial Results

Todd C. Wehner and Conrad H. Miller

Department of Horticultural Science, North Carolina State University, Raleigh, NC 27650

Plant breeders usually test new experimental lines for several years in replicated, multiple-harvest trials to determine whether the line should be released for production in a particular growing area. However, because of limitations on the amount of land available for trials, or on the amount of seed available for each experimental line, trials are often planted with unbordered plots. Thus, border rows are used only around the outside of the trial so that the lines are not being tested in monoculture, but rather in mixed plantings with different genotypes in adjacent plots.

Competition between different genotypes has been recognized as an important factor causing bias in yield trials of some crops, such as soybean (2). Unbordered plots of soybeans are acceptable for the northern U.S.A., but not for the southern U.S.A. where more foliage growth occurs (1). The objective of this experiment was to determine whether unequal competition occurs in pickling cucumber yield trials planted with unbordered plots.

Methods. Two hybrids (‘Calypso’ and ‘Southern Belle’) and an inbred (‘M 21’), all developed at North Carolina State University, were chosen as pickling cucumbers adapted to the area that had different growth habits. ‘Calypso’ is a tall, indeterminate cultivar, ‘M 21’ is a dwarf, determinate line, and ‘Southern Belle’ is a medium-size, indeterminate cultivar. The 3 lines were planted May 17, 1982 in 3-row plots 4.6 m wide and 6 m long in a randomized complete block design with 6 replications. The 3 lines were planted in 9 combinations of border and center rows. Thus, each of the 3 lines were planted in center rows with either ‘Calypso’, ‘Southern Belle’ or ‘M 21’ in the border rows to simulate bordered or unbordered plots. The center row of each plot was harvested 6 times (twice weekly) from June 24 through July 12. Fruit were graded into 4 sizes by diameter (No. 1 was <26mm, No. 2 was 27–38 mm, No. 3 was 39–50 mm, No. 4 was >51 mm), counted and weighed. Fruit value ($/ha) was calculated using $0.31, $0.14, $0.09, and $0.00 dollars/kg for grades 1, 2, 3 and 4 respectively ($14.00, 6.50, 4.00 and 0.00 dollars/cwt, respectively).

Results. Yield of the dwarf line, ‘M 21’, was significantly reduced when it was grown adjacent to rows of the tall cultivars, ‘Calypso’ and ‘Southern Belle’ (Table 1), Yield of ‘M 21’ was reduced 13% from that of bordered plots (‘M 21’ in the border rows) when the medium-size cultivar, ‘Southern Belle’, was grown in the border rows, and 20% when the large cultivar, ‘Calypso’, was grown in the border rows.

Table 1. Yield of 3 pickling cucumber lines in bordered (same line in border rows) and unbordered (different line in border rows) plots.z


Line planted in the 3-row plot


Total yield


Yield ($/ha) in harvest


Center

Borders

$/ha

q/ha

1

1–2

1–3

1–4

1–5


M 21

M 21

2511b

435b

277b

 672b

1281b

1918b

2091b

 

S. Belle

2192*

392ns

290ns

 657ns

1119+

1649*

1814*

 

Calypso

1999**

353*

271ns

 555ns

 980**

1505**

1647**

 

 

 

 

 

 

 

 

 

S. Belle

M 21

2161ns

495ns

623ns

1080ns

1498ns

1876ns

1973ns

 

S. Belle

2054b

463b

584b

1052b

1442b

1788b

1870b

 

Calypso

2118ns

506ns

557ns

1073ns

1444ns

1803ns

1929ns

 

 

 

 

 

 

 

 

 

Calypso

M 21

2014ns

492ns

503ns

1124+

1470ns

1782ns

1862ns

 

S. Belle

1935ns

481ns

515ns

 975ns

1315ns

1651ns

1762ns

 

Calypso

1954b

475b

473b

 990b

1356b

1661b

1771b

 

 

 

 

 

 

 

 

 

LSD (5%)

 278

 71

 80

 148

 180

 224

 226

Mean (all treatments)

2104

454

455

 909

1323

1737

1858

CV (%)

  11

 13

 15

  14

  12

  11

  10


zVine lengths at first harvest for ‘M 21’, ‘Southern Belle’ (S. Belle) and ‘Calypso’ were 37, 47 and 67 cm, respectively. Data are means over 6 replications and 6 harvests.

ns,+,*,**Yield not significantly different from bordered plot (b), and significantly different at the 10, 5 and 1% levels, respectively.

Cumulative yield of unbordered plots of ‘M 21’ was reduced both in fruit value and in fruit weight, but only after the second harvest (of 6). That indicated that problems occurred only after the cultivars in the border rows grow large enough to compete with the dwarf plants in the center row of the plot.

Yields of ‘Calypso’ and ‘Southern Belle’ were not significantly affected by the presence of either tall or dwarf lines in adjacent rows. Thus, it appears that yield trials can be conducted with unbordered plots, provided that dwarf, determinate lines are tested in separate trials from tall, indeterminate lines.

Literature Cited

  1. Hanson, W. D., C. A. Brim and K. Hinson. 1961. Design and analysis of competition studies with an application to field plot competition in the soybean. Crop Sci. 1:255–258.
  2. Schutz, W. M. and C. A. Brim, 1967. Inter-genotypic competition in soybeans. I. Evaluation of effects and proposed field plot design. Crop Sci. 7:371–376.
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Page citation: Wehner, T.C., Cucurbit Genetics Cooperative;
Created by T.C. Wehner and T. Ng, 1 June 2005; design by C.T. Glenn;
send questions to T.C. Wehner; last revised on 1 August, 2007