Genetic Improvement in Short Season Soybeans: I. Dry Matter Accumulation, Partitioning, and Leaf Area Duration

Abstract

Genetic improvement of short‐season soybean [Glycine max (L.) Merr.] cultivars has resulted in a 0.5% annual gain in yield. Although yield is the product of dry matter (DM) accumulation and partitioning, the relative contributions of these two components of yield to genetic improvement has not been documented. Furthermore, the mechanism by which higher DM accumulation or harvest index (HI) is accomplished in the newer cultivars is unclear. The objective of the current study was to characterize DM accumulation and partitioning in cultivars which differ in yield potential, and determine the role of these traits in yield improvement. Two older (low yield potential) and two newer (higher yield potential) soybean cultivars of similar maturity were grown in side‐by‐side trials in 1996 and 1997. Plant samples were taken during each growing season and separated into leaves, stems + petioles, roots, and seeds. Dry matter accumulation and leaf area indices were measured. Seed yield of the new cultivars was 30% greater than their older counterparts. Increased DM accumulation contributed 78% and increased HI contributed 22% towards the genetic gain in yield. Total plant dry weight increased to a maximum around R4/R5 and subsequently declined during the seed‐filling period (SFP) as pod development increased and leaf senescence began. This decline in dry weight during the SFP was greater for the old than for the new cultivars. The newer cultivars maintained leaf area further into the SFP than the old cultivars enabling continued dry matter accumulation. The results of this experiment indicate that genetic yield improvement in the short‐season soybean cultivars examined was mainly associated with longer leaf area duration and the subsequently greater DM accumulation.

Dry Matter and Nitrogen Uptake, Partitioning, and Removal across a Wide Range of Soybean Seed Yield Levels

“…1 and 2, Table 6). This supports the importance of new cultivar releases exhibiting greater total DM production associated with higher yields (Kumudini et al, 2001;De Bruin and Pedersen, 2009). …”

“…Multiple reports point to both increased total DM and a greater HI for new genetics within current production systems (Sadler and Karlen, 1995;Sinclair, 1998;Morrison et al, 1999;Kumudini et al, 2001;Koester et al, 2014;Rincker et al, 2014). Koester et al (2014) found that HI increased by 0.0022% each year between 1923 and 2007 for commercially available varieties.…”

Investigating of N and K Fertilizers on Yield and Components of Soybean (Glycine max (L.) Merr.)

“…Our findings were in line with the other observations by Showkat and Tyagi (2010) and Arshad et al (2006) who reported that positive and significant correlation were among yield, number of pods per plant and 100 seed weight. Kumudini et al (2001) also concluded that there is a significant and positive correlation between yield and component of soyebean. Shiraiwa et al (2004) reported pod seed number as determinant factors of soybean yield.…”

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

“…According to Kumudini et al (2001), new cultivars of early maturity group, presented heavier seeds, but the same number of seeds, when compared with the old cultivars of the same maturity group, and attributed this fact to larger number of days and seed filling rate. The authors cited that the new cultivars of late maturity group, presented higher number of seeds per area when compared with old cultivars, but the specific mass of seeds was not different.…”