Partial Resistance to Soybean Rust in Diverse Soybean Germplasm Under Field Conditions in Uganda

ABSTRACT Soybean rust (SBR), caused by Phakopsora pachyrhizi , poses a major threat to global soybean production, particularly in sub‐Saharan Africa, where it impacts food security and agricultural sustainability. This study aimed to (i) screen a genetically diverse panel of soybean accessions, including African (Uganda, Zimbabwe and Nigeria), Asian (Taiwan and Japan) and North American (United States) germplasm for partial resistance to SBR, and (ii) estimate the heritability of resistance‐related traits. The genotypes were divided into two groups (G1 and G2), based on observed days to maturity, and phenotyped at the R6 growth stage. Best linear unbiased predictions (BLUPs) were estimated for rust index (RI) and lesion type (LT). G1 showed BLUPs ranging from −0.41 to 0.75 for RI and −0.48 to 0.63 for LT, with Ux 990‐072, Ux 990‐004 and Dassel ranking highest for partial resistance. G2 revealed a broader variation (RI: −1.3 to 0.36; LT: −0.88 to 0.32), with SS86045‐23‐2B, AGS 329 and G2043 identified as top partial resistance candidates. RI heritability was moderate in G1 ( H 2  = 0.56) and high in G2 ( H 2  = 0.67), while LT showed moderate heritability in both populations ( H 2  = 0.58–0.60). RI and LT were strongly correlated ( r  = 0.833–0.887; p  < 0.001), confirming LT as a semiquantitative trait and RI as an effective selection index. The results confirm exploitable genetic variation for partial resistance, identify candidate genotypes for breeding, and provide a foundation for targeted QTL mapping and KASP SNP marker development, advancing genomic‐assisted breeding for durable SBR resistance cultivars in Africa.