Crop Growth Rate and Seeds per Unit Area in Soybean

Abstract

The number of seeds per unit area is an important yield component in soybean [Glycine max (L.) Merr.]; however, the mechanisms responsible for the regulation of this yield component are not well understood. Field experiments were conducted at Lexington, KY (3 yr), and at Taian, China (1 yr), to investigate the relationship between net canopy photosynthesis and seeds per unit area using genotypes with differences in individual seed growth rates (SGR). At Lexington, shades (30 and 63% reduction in insolation) were placed over plots from growth stage Rl until maturity to create differences in canopy photosynthesis. Planting dates (early and late) and row spacing (wide and narrow) were used at Taian to create differences in canopy photosynthesis. Crop growth rate (CGR) was measured between growth stage Rl and RS as an estimate of net canopy photosynthesis. Yield, seeds per m2, and SGR were also measured. Within each genotype, there was a linear relationship between CGR and seeds per m2 across treatments and years. Within an experiment, seeds per m2 at a constant CGR was inversely related to genotypic differences in SGR. A partitioning coefficient (γ) was estimated by dividing the total sink demand (seeds per m2 ✕ SGR) by CGR. There were no apparent genotypic differences in γ however, γ decreased linearly as CGR increased. The data suggest that the model proposed by Charles‐Edwards, which describes seeds per m2 as a direct function of canopy photosynthesis and a partitioning coefficient and an inverse function of assimilate flux to individual seeds, accurately describes the regulation of seeds per m2 in soybean.

Correlation between Yielding Ability and Dry Matter Productivity during Initial Seed Filling Stage in Various Soybean Genotypes

“…The above results do not agree with the well recognized concept that pod or seed number and hence yield depend on assimilate supply during a period before R5 (Shou et al, 1978;Kokubun and Watanabe, 1983;Egli and Yu, 1991;Board and Harville, 1993;Jiang and Egli, 1995). Our results rather support the view of Specht et al (1999) and Shiraiwa and Hashikawa (1995), who reported that higher yields in modern cultivars than in old cultivars correlated with their greater dry matter production during the seed fi lling period.…”

“…In soybean, variation in yield is generally correlated with either pod number or seed number. Several studies that focused on development of reproductive organs revealed that the assimilate supply during fl owering and pod set contributed highly to high yield (Schou et al, 1978;Kokubun and Watanabe, 1983;Kokubun, 1988;Egli and Yu, 1991;Board and Harville, 1993;Jiang and Egli, 1995). Recently, a higher number of fl orets, which would be supported by assimilate supply around the beginning of fl owering or even earlier, has been suggested to contribute to improvement of yield (Kohri et al, 1998).…”

Sowing Dates and Soybean Cultivars Influence Seed Yield, Oil and Protein Contents in Subtropical Environment

“…According to Egli and Yu (1991) there is also a linear positive correlation between the crop growth rate between R 1 -R 5 growth stages with the number of seeds. In the present study, during the R 1 -R 5 growth stage, the cultivar BRS 284 presented the higher crop growth rate (data not shown), and probably because of this fact produced higher number of seeds per area.…”

Interrelationships among yield components of chickpea in semiarid environments

“…This type of information is also useful for chickpea breeders to establish selection criteria in genetic manipulation. For example, selection for highyielding cultivars through specific traits requires knowledge not only on the mechanisms of seed yield formation but also on the physiological processes relative to setting pods (Egli and Yu 1991), forming the seed number (Board and Tan 1995), and filling these potential fruiting sites (Ball et al 2001).…”