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Cucurbit Genetics Cooperative Report 5:40-41 (article 20) 1982

Dry Matter Accumuilation and Productivity in Bush and Vine Strains of Winter Squash

C. E. Broderick and J. B. Loy

University of New Hampshire, Durham, N.H. 03824

The bush phenotype facilitates conventional row culture and manageability of winter squash, however, there is little information regarding comparative photosynthgetic efficiency and productivity between bush and vine forms of C. maxima.

In 1980 and 1981, field experiments were carried out to compare yields and the partitioning of dry matter in a bush and vine strain of winter squash. 'Blue Hubbard' was selected as the vine strain because of its vigor and high yielding capability. The bush strain (30-11-31-9) was a large-fruited, vigorous inbred which normally sets one fruit per plant with close spacing.

'Blue Hubbard' and 30-11-8-1 were about equally productive at the 5,600 plants/ha density (Table 1) a spacing shown to be near optimum for 'Blue Hubbard'. Highest yields for the bush strain occurred at the highest planting density, however, fruits were small and often misshapen, and exhhibited lower percent dry matter at this density. A plant density of about 10,000 plants per hectare is considered optimum for the bush strain, but this could vary depending on location, plant vigor, and time of flowering. Percnet dry matter was low in both bush and vine strains in 1981 due to powdery mildew infestation in the spacing trial.

Table 1. Yield of a bush strain (30-11-8-1) at different plant densities as compared to yield of 'Blue Hubbard' planted at near optimum plant density.

 
1980
1981

Plant Density

pls./ha

kg/ha

Fr.Wt.

kg/pl

Fr.Wt.

kg/ha

Fr.Wt.

kg/ha

Dry Wt.

Kg/pl

Fr.Wt.

Bush

22,000 (0.3 x 1.5 m)

77,000
3.7
74,800
5,310
3.5

11,000 (0.6 x 1.5 m)

70,300
6.6
61,500
4,551
5.5

7,400 (0.9 x 1.5 m)

64,600
9.0
55,300
4,313
7.7

5,600 (1.2 x 1.5 m)

61,300
10.6
52,200
4,594
9.2
Vine

5,600 (1.2 x 1.5 m)

57,300
10.4
50.700
4,867
8.7

Above-ground dry matter acumulation was initially similar in 'Blue Hubbard and 30-11-8-1 plants grown under nono-competitive (low density) spacings (Table 2). With the onset of multiple secondary and tertiary branching in vine plants, total dry matter rose rapidly. Peak dry matter occurred earlier in the bush strain, and dry matter actually declined between 10 to 12 weeks from transplanting, due to early fruit maturity and onset of leaf senecence. Net assimilation rate (NAR) and harvest index were higher in the bush strain. This together with the rapid leaf canopy development of the bush strain under high density planting probably contributed to its high productivity.

Table 2. Dry matter accumulation and distribution in bush and vine strains of winter squash grown at low density planting.

Sample Times (Weeks from Transplanting
Total Plant Dry Wt.

NARy

g/dm2 leaf

% Dry Wt.

Fruit/Total

Bush
Vine
Bush
Vine
Bush
Vine
4
59
67
1.0
0.8
--
--
6
725
978
1.6
1.6
17.8
3.2
8
2555
2514
2.4
1.9
--
--
10
3125
8174
3.7
2.5
--
--
12
2575
9471
5.7
2.8
69.6z
57.0z

yNet assimilation rate (cumulative).
zEquivalent to harvest index (includes both green and mature fruit of 'Blue Hubbard).

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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