Description of experimental breeding lines

The seven breeding lines and nine check cultivars evaluated in this study are shown in Table ​Table1.1. Breeding lines 04025-41, 25-1-1-4-1-1, and 34-3-1-2-4-1 were derived from PI 587982A, which was identified by Smith et al. (2008) to have high germinability. The other parent for each of the above three lines was DT98-9102, DT98-9102, and DT97-4290 (Paris et al., 2006), respectively. Breeding line 24-2-1-2-1-2 was derived from DT98-9102 × PI 603756. The latter PI was also identified by Smith et al. (2008) as having high germinability. Each of the above breeding lines is considered to have 50% exotic parentage. Breeding lines LG03-4561-14 and LG03-4561-19 are sister lines from the same F₂ plant developed by R.L. Nelson and adaptively selected by J.R. Smith for the ESPS. These two lines have 19% exotic parentage derived from PIs 68508 and 445837. Their immediate parents are LG99-5106 and LG97-9226. Breeding line LG04-1459-6 is derived from S32-Z3 × LG00-3056, but has 25% exotic parentage from PIs 361064, 407710, 189930, and 68600. Two public cultivars from Illinois were included in the study; Dwight (Nickell et al., 1998) and LD00-3309 (Diers et al., 2006). Five commercial cultivars (AG3803, AG3905, AG4403, AG4903, and AG5606) developed by the Monsanto Corporation were included, along with one cultivar developed by Hornbeck Seed Company (C4926) and one cultivar developed by Delta King seed company (DK4866). The genotypes used here were categorized into three groups: (1) breeding lines derived from exotic parental accessions and previously identified to have high germinability under irrigation in the ESPS (04025-41, 25-1-1-4-1-1, 34-3-1-2-4-1, and 24-2-1-2-1-2; all 50% exotic); (2) cultivars (checks); and (3) breeding lines derived from exotic parental accessions and previously identified to have high yield potential under irrigation in the ESPS [(LG03-4561-14 and LG03-4561-19, 19% exotic); (LG04-1459-6, 25% exotic)].

The 16 soybean genotypes grown under dryland conditions in a 2-year field experiment.