Morpho-Physiological Aspects of Productivity and Quality in Squash and Pumpkins (Cucurbita spp.)

Abstract

Squash and pumpkins are important horticultural crops worldwide, but there has been relatively little research to systematically describe yield components and improve productivity in this species. This review outlines some of the basic growth-analysis techniques for describing different aspects of productivity and attempts to summarize investigations on physiological, morphological, and ecological aspects of productivity and the relationship of these factors to eating quality in the three most important domesticated species of Cucurbita—C. pepo, C. maxima, and C. moschata. The emphasis of this review is on components of yield that can be modified either by selective breeding or through use of cultural techniques. Increasing economic crop yield while also balancing the needs to maintain and improve culinary qualities of the edible product will also be discussed. The bush phenotype is being increasingly exploited in new cultivar development. Advantages and disadvantages of using bush genotypes in cultivar development are addressed. In addition, because of increasing use of Cucurbita seeds for vegetable oils, snackseeds, and pharmaceutical purposes, physiological components of seed yield are also discussed.

Keywords:

• squash
• pumpkin
• Cucurbita species
• crop growth rate
• harvest index
• leaf area index
• fruit yield
• seed yield
• breeding strategies
• fruit quality

ACKNOWLEDGEMENTS

The author wishes to thank Drs. Donald N. Maynard and David Kopsell for critical reviews of this manuscript, and Drs. Donald N. Maynard and Douglas G. Grant for providing helpful resources.

Notes

∗Data represent total flower numbers from 4 replications, 20 plants per plot. Plant grown at the Kingman Research Farm, Madbury, NH, USA in 1999.

^a Data extrapolated from Tables 3 and 4 in Cui and Loy (2002) using a value of 92.5 for % embryo to total seed weight from Vining (1999).

^b Data are average of 4 replications and 18.4 fruit/plot from 13 plant plots.

^c Data extrapolated from biomass data of 10 kabocha and 8 acorn fruit harvested in 2002. Embryos comprised 55% of seed weight in tan-seeded kabocha and 78% of seed weight in acorn. Maximum DW of acorn pericarp tissue was only 12.2% for the cultivar Mesa Queen, so ratio of seed to total biomass is higher than expected.

^d kJ for seed (24.85/g) obtained from proximate analysis of Medallion Laboratories, Minneapolis, MN; kJ for pericarp (12.55/g) extrapolated from food values given in Bowes and Church (1970).

^e E = embryo; Fr, fruit.

^a Mean separation by Duncan's Multiple Range Test, 5% level.

^b Means ± SD, 5 replications.

^a Experiments conducted by Cui and Loy at the Woodman Horticultural Research Farm, Durham, NH, USA in 2003, using a randomized complete block design with 4 replications. Plant spacing was 0.3 m × 1.8 m.

^b Days after pollination (DAP) are given as average days for samples taken 7–9 days, 23–25 days, and 40–45 days, respectively, for the first three sampling periods.

^c Values ± SD are means of 4 replications and 3 plants per replication, except for final harvest which included fruits from 15 plants per replication.

^d Leaf areas were calculated from leaf DW × specific leaf weights, based on 10 samples per plant taken from the mid portion of leaves with a 4.9 cm punch.

^a Experiments conducted at the Woodman Research Farm, Durham, NH, USA using a randomized complete block design, with 5 replications and 2 plants per plot in 1982, and 8 replications of single plants in 1983. Plant spacing was 0.9 × 1.8 m.

^b Total pericarp dry weight (DW) determined by % pericarp DW × pericarp FW. Pericarp FW equals total fruit FW − estimated seed FW.