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Cucurbit Genetics Cooperative Report 5:20-21 (article 10) 1982

Correlation of Multiple-harvest Yield with Once-over Yield in Small Plots for Fresh-market Cucumbers

Todd C. Wehner and Conrad H. Miller

North Carolina State University, Raleigh, NC 27650

Probably the most accurate method of measuring yield of fresh-market cucumber lines is through a multiple-harvest trial with large replicated plots. However, in a breeding program, it is usually necessary to evaluate more one type than can be practically handled with that method. For pickling cucumber, there is a significant correlation of once-over with multiple-harvest yield (2). Furthermore, since fruit weight and fruit value change during fruit set and development, once-over yield is best measured using fruit number (1). Selection for yield in fresh-market cucumbers could be made easier if fruit could be harvested once from small plots and counted. The value of that approach was tested by correlating yield from small plots harvested once with yield in a replicated multiple-harvest trial.

Ten hybrids were made up by crossing 20 diverse lines paired at random. The hybrids were tested in a multiple-harvest trial in a randomized complete block design with 4 blocks and 7 harvests. Harvests were made twice weekly from July 23 to August 13. Plots were 7.5m long with 1.5 m alleys at each end, and were on 1.5m centers. Plots were seeded on raised beds with 0.5m tops at a population of 84,000 plants/ha.

The same hybrids were also planted in similarly arranged 3m plots in the same location. The plots were harvested once-over at the stage where 10% oversize fruits were present. Total number and marketable number of fruit were counted, and the data were correlated with the yield results from the multiple harvest trial. The once-over harvest experiment was replicated 4 times to measure the variability associated with the correlations with multiple-harvest yield.

The highest correlations were between total once-over harvest fruit number and total multiple-harvest fruit number or fruit weight (Table1). Slight correlations existed for marketable fruit number for the once-over vs. multiple-harvest results. Correlations for marketable yield in the once-over harvested plots were not significant in some of the blocks, especially block 2. Therefore, replication of the plots would probably be necessary to provide more reliable results for selection for marketable yield.

Table 1. Pearson product-moment correlations for once-over vs. multiple-harvest yield by fruit number (fruit weight) cumulative for harvests 1-7).

Block
Total Fruit Yield
Marketable Fruit Yield
1
.58+ (.68*)
.63+ (.63+)
2
.70* (.47)
.35 (.29)
3
.72* (.66*)
.48 (.48)
4
.73* (.57+)
.53 (.41)
Mean
.68* (.60*)
.50+ (.45)

+,* Significant correlation at the 10 and 5% levels, respectively.

Once-over harvested plots were most highly correlated in yield with the multiple-harvest yield from all 7 harvests (Table 2). The once-over harvest was made at the same time as harvest 4 of the multiple-harvest trial, so it was surprising that the correlations increased throughout the 7 harvests without a peak around harvest 4.

Table 2. Pearson product-moment correlations for once-over vs. cumulative multiple-harvest yield for marketable fruit number (total fruit number).

Harvest
Block
1
1-2
1-3
1-4
1-5
1-6
1
.66*(.50)
.69*(.57+)
.67*(.70*)
.61(60+)
61+(.63*)
.62+(.60+)
2
-.12(-.12)
-.08(-.06)
.17(.29)
.16(.44)
.22(.49)
.31(.61+)
3
.16(.18)
.24(.23)
.43(.58+)
.37(.56+
.40(.63+)
.46(.69*)
4
.23(.29)
.23(.29)
.37(.52)
.36(.60+)
.40(.65*)
.48(.67*)
Mean
.23(.21)
.27(.26)
.41*(.52**)
.38*(55**)
.41*(.60**)
.47**(.64**)

+,*,** Significant at the 10, 5, and 1% levels, respectively.

In conclusion, total fruit number from small plots harvested once is correlated with multiple-harvest yield. Furthermore, the correlation is high enough to make it a good method for evaluating large numbers of genotypes or progeny rows in a selection program. Marketable fruit number was not as well correlated with multiple-harvest trial results, so fruit quality should be monitored carefully while selecting for yield.

Literature Cited

  1. Ellis, J. E. and A. E. McSay. 1981. Yield comparisons of pickling cucumber cultivar trials for once-over harvesting. HortScience 16:187-189.
  2. Smith, O. S. and R. L. Lower. 1978. field plot techniques for selecting increased once-over harvest yields in pickling cucumbers. J. Amer. Soc. Hort. Sci. 103-92-94.
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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 23 October, 2009