Abstract Four soybean Glycine max (L.) Merr. lines, two with lanceolate (narrow) leaf shape (LD11‐NL‐1 Reg. no. GP‐549, PI 708601, LD11‐NL‐2 Reg. no GP‐550, PI 708602) and two with ovate (broad) leaf shape (LD11‐BL‐1 Reg. no GP‐547, PI 708599, LD11‐BL‐2 Reg. no GP‐548, PI 708600) were developed at the University of Illinois Urbana‐Champaign and released to investigate the effects of leaf shape on soybean physiology and productivity. These lines were developed through three generations of backcrossing (BC 3 ) the ln allele for narrow leaf shape from the narrow‐leaved donor parents PI 612713A and PI 547745 into the elite broad‐leaved cultivar ‘LD11‐2170’, followed by selfing to generate BC 3 F 2 ‐derived F 4 lines. Marker‐assisted selection using JAG1 gene‐specific Kompetitive Allele Specific polymerase chain reaction markers was conducted during backcrossing and in the BC 3 F 2 generation. The four selected near‐isogenic lines share ∼95% genetic similarity with the recurrent parent LD11‐2170, and differ principally at the GmJAG1 locus, enabling precise study of the effects of leaf shape on soybean development, growth, and productivity. Leaf Area Index (LAI) in the narrow‐leaved lines was 14%–16% lower on average across growth environments compared with broad‐leaf lines. There were modest differences in the time to canopy closure, but no yield advantage was observed for narrow‐leaf lines across environments and row spacings. Notably, narrow‐leaved lines produced significantly more 4‐seeded pods (34.2% vs. 1.8%). These germplasm resources will facilitate investigation into the physiological mechanisms underlying canopy architecture optimization and enable breeding for improved radiation‐use efficiency in soybean, helping address the excessive LAI often seen in modern varieties.
Tamang et al. (2026) studied this question.