Natural genetic variations in waterlogging tolerance are controlled by multiple genes mapped as quantitative trait loci (QTLs) in major crops, including soybean (Glycine max L.). In this research, 2 novel QTLs associated with waterlogging tolerance were mapped from an elite/exotic soybean cross. The subsequent research was focused on a major QTL (qWT_Gm03) with the tolerant allele from the exotic parent. This QTL was isolated into near-isogenic backgrounds, and its effects on waterlogging tolerance were validated in multiple environments. Fine mapping narrowed qWT_Gm03 into a genomic region of <380 Kbp excluding Rps1 gene for Phytophthora sojae resistance. The tolerant allele of qWT_Gm03 promotes root growth under nonstress conditions and favourable root plasticity under waterlogging, resulting in improved waterlogging tolerance, yield, and drought tolerance-related traits, possibly through more efficient water/nutrient uptakes. Meanwhile, involvement of auxin pathways was also identified in the regulation of waterlogging tolerance, as the genotypic differences of qWT_Gm03 in waterlogging tolerance and formation of adventitious/aerial roots can be complemented by an exogenous auxin-biosynthesis inhibitor. These findings provided genetic resources to address the urgent demand of improving waterlogging tolerance in soybean and revealed the determinant roles of root architecture and plasticity in the plant adaptation to waterlogging.

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Soybean (Glycine max [L.] Merr.) meal is the largest source of protein meal with essential amino acids. Soybean seed protein is negatively correlated with both yield and oil, complicating the simultaneous improvement of seed protein and yield. A major protein quantitative trait locus (QTL) on chromosome (Chr) 20 was identified in genome‐wide association and bi‐parental population mapping studies. The Chr 20 high‐protein allele from ‘Danbaekkong’ was introgressed into an elite maturity group (MG) VII cultivar, Benning. Two groups of near‐isogenic lines (NILs) of Benning, with or without the Danbaekkong Chr 20 allele, were developed and yield‐tested in two years. The Danbaekkong allele was associated with a significant 33.6 g kg–1 increase in protein and 14.3 g kg–1 decrease in oil (P < 0.05). Average yield of NILs with the Danbaekkong allele were lower than those of NILs without the allele and recurrent parent Benning in both years, but were only significantly lower in 2005 (P < 0.05). Due to its high yield performance, one NIL was yield tested against Benning for two additional years. Combined results from 14 environments over four years revealed yield parity between Benning and Benning high protein (HP), and Benning HP possessed 40.0 g kg–1 more seed protein and 17.3 g kg–1 less oil than Benning. Despite overall yield drag by the Danbaekkong Chr 20 high‐protein allele, we demonstrate that a significant increase in seed protein without associated reduction in yield is possible with breeding and careful progeny selection using this allele.

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Rosette, incited by Cercosporella rubi (G. Wint.) Plakidas, is the most severe disease of blackberries in the southern United States. Sixteen blackberry cultivars and breeding selections were evaluated in a field test over a 3-year period for incidence and severity of rosette. Test plots were planted in a randomized complete block design with four replications. A plot consisted of a 3-m hedgerow of blackberry canes. Each test plot row was bordered on each side by a row of the rosette-susceptible cultivar Shawnee. Disease ratings were conducted on five random floricanes in each plot. Disease severity was rated with a 1 to 8 scale (1 = 0% floricane nodes with rosettes, 2 = 0% to 10%, 3 = 10% to 25%, 4 = 25% to 50%, 5 =50% to 75%, 6 = 75% to 90%, 7 = 90% to 100%, 8 = 100%). `Shawnee' and `Rosborough' had high incidence and severity. Cultivars and selections with moderate-high incidence and low-moderate severity were `Brazos', `Cheyenne', `Choctaw', A-1260, A-1442, A-1560, and A-1585. Cultivars and selections with zero-low incidence and severity were `Arapaho', `Humble', `Navaho', A-1374, A-1594, A-1616, and A-1617.