Reniform nematode (Rotylenchulus reniformis) is a damaging and difficult-to-manage pest on many agricultural crops. Sorghum and sorghum-sudangrass hybrids (SSgHs) have shown potential in managing plant-parasitic nematodes by releasing toxic hydrogen cyanide gas through the hydrolysis of dhurrin, a cyanogenic glucoside found in leaf epidermal cells. The objectives of this study were to evaluate the effect of different SSgH varieties and their age on the suppression of R. reniformis and to quantify their dhurrin contents. Shoot biomass of seven SSgH varieties was harvested at 1, 2, and 3 months of growth and used as a soil amendment in two greenhouse cowpea bioassay trials. Dhurrin concentration was analyzed using high-performance liquid chromatography from 2-month-old tissues. The results indicated that energy sorghum 'NX-D-61' and SSgH 'Latte' exhibited the highest dhurrin concentrations (P <= 0.05) and suppressed R. reniformis development in cowpea roots (P <= 0.05). In Trial I, 2-month-old amendments showed the greatest suppression, whereas in Trial II, 1-month-old amendments were more suppressive (P <= 0.05). Potential effect of environmental stress on dhurrin concentration in SSgH tissue was discussed. Nonetheless, dhurrin concentrations were negatively related to the number of R. reniformis infecting cowpea roots (R2 = 0.69; P = 0.02). These findings suggest that high-dhurrin SSgH varieties can be integrated into reniform nematode management plans as a cover crop and terminated no more than 2 months after planting.

Rotylenchulus reniformis poses a significant threat to cotton crops in the Brazilian Cerrado, particularly when grown consecutively with soybeans. This nematode has not only become a concern for cotton but has also led to considerable damage in soybean crops, emphasizing the need for effective nematode control in both agricultural settings. The aim of this study was to combine genetic control with the application of biological nematicides, as seed treatment, to manage R. reniformis under greenhouse conditions. Two soybean cultivars, TMG 4182 and Fibra, resistant and susceptible, were used and the biological nematicides used included Purpureocillium lilacinum, Trichoderma harzianum + T. asperellum + Bacillus amyloliquefaciens, B. subtilis + B. licheniformis, and B. firmus. Inoculation with 800 R. reniformis occurred in the cotyledonary stage, with evaluations conducted at 72 and 76 days after inoculation for Experiments 1 and 2, respectively. Nematodes were extracted from the soil and roots, calculating the reproduction factor (RF). The combination of biological nematicides with resistant cultivars did not yield substantial benefits in controlling reniform nematodes in soybean but safeguarding resistant cultivars through the application of chemical or biological nematicides is important to mitigate inoculum pressure on resistance genes. In addition, biological nematicides evaluated in this study did not improve soybean plant development and we concluded that managing reniform nematodes in soybean necessitates the integration of diverse control measures to effectively address the challenges posed by this nematode's impact on crops.