Occurrence, distribution, and genetic diversity of the cyst nematode <i>Heterodera glycines</i> Ichinohe, 1952 infecting red kidney beans in Shanxi Province, China

The soybean cyst nematode (Heterodera glycines) poses a significant constraint on the production of red kidney beans (Phaseolus vulgaris) in Shanxi Province, China. To elucidate its epidemiological dynamics and population genetics within this cropping system, we conducted field surveys from 2020 to 2022 across 11 counties in the primary red kidney bean-producing cities of Taiyuan, Xinzhou, and Lvliang. Our results revealed that H. glycines was detected in all surveyed counties, with cysts identified in 98.8% of the 164 field samples collected. Population densities ranged from 74.6 cysts per 100 g of soil in Kelan County (an epidemic hotspot) to 8.0 cysts per 100 g of soil in Yuanping County (baseline levels). Analysis of ITS rRNA gene sequences indicated that genetic variation predominantly occurred within populations (Fst = 0.12499; Nm = 1.7502), whereas significant genetic divergence was associated with different host plants (Fst = 0.25217; Nm = 0.7414). Phylogenetic and haplotype analyses further indicated that populations infecting red kidney beans formed a distinct cluster separate from those associated with other hosts. These findings highlight host adaptation as a key evolutionary driver and provide a critical foundation for targeted management strategies against H. glycines in red kidney bean production systems.