PHENOTYPIC VALIDATION OF CORN HYBRIDS WITH LOW REPRODUCTION FACTORS FOR PRATYLENCHUS BRACHYURUS

Abstract

       In Brazil, corn is primarily grown in succession to soybeans. However, certain nematodes, such as Pratylenchus brachyurus multiply on corn, increasing in density and impacting subsequent crops. There is currently no standardized methodology for phenotyping corn for host response to P. brachyurus, and some hybrids have shown inconsistent results in the field. The objective of this study was to evaluate the reproduction factor (RF = final nematode density/initial nematode density) of P. brachyurus in eight different corn hybrids, previously identified as having low RF values for this nematode, across two different time points, in two experiments. Eight corn hybrids were sown and maintained in a greenhouse under controlled conditions (28°C ± 2°C). At the first vegetative growth stage, each plant was inoculated with 500 P. brachyurus. Roots were collected at 76 and 97 days after inoculation (DAI), then washed, weighed, and nematodes extracted. The fresh root weight (FRW) and the number of nematodes and eggs were used to calculate the number of nematodes per gram of roots (Nema/g) and the RF values for each hybrid. The experiment was conducted in a completely randomized design with an 8x2 factorial arrangement and 7 replicates each. A significant difference in RF values was observed between the two evaluation dates. At 97 DAI, none of the hybrids had low RF values, differing from the evaluation at 76 DAI, in which the majority of hybrids were classified as resistant. The findings of this study suggest that assessing the resistance or susceptibility of corn hybrids to P. brachyurus shortly after inoculation can produce inconsistent results. This variability could hinder effective nematode management in the field, as these hybrids may still contribute to increasing soil nematode densities, negatively affecting subsequent crops in the rotation.