Temporal dynamics of root penetration by Meloidogyne javanica and Pratylenchus brachyurus in soybean

Nematodes are major constraints to agricultural productivity in tropical countries. Despite the strong influence of infection dynamics on the efficiency of management strategies, there is scarce information about the rate at which these parasites penetrate plant roots. This study aimed to characterize the early penetration dynamics of Meloidogyne javanica and Pratylenchus brachyurus in soybean. For each nematode species, two greenhouse trials were conducted at different times. Nematodes were inoculated at sowing, and penetration was evaluated at 2, 4, 6, 8, 10, and 12 days after inoculation (DAI). Nematodes were quantified by root staining with acid fuchsin. For M. javanica , a quadratic regression model provided the best fit to penetration data in both trials, with the first individuals penetrating at 4 DAI. Logistic regression indicated delayed infection behaviour, followed by an abrupt increase in penetration, reflected by t 50 (time at which 50% of plants were infected) values of 3 and 4 DAI and Firth estimates of 2.35 and 1.21 log ratios. For P. brachyurus , Trial 1 data were best fitted by a linear model and Trial 2 data by a quadratic model, with the first individuals penetrating at 2 DAI. This species exhibited early and proestimate infection, as shown by t 50 values of 2.2 and 1.6 DAI and Firth estimates of 1.13 and 0.71 log ratios. The results revealed distinct infection patterns between the two species, with an exponential pattern for M. javanica and a more linear pattern for P. brachyurus . Quantitative and probabilistic analyses were complementary and provided a broader understanding of the early infection process of these nematodes in soybean.