Reaction of Stylosanthes spp. 'Campo Grande' to Pratylenchus brachyurus and Meloidogyne javanica and analysis of the histopathology and histochemistry of their interactions

Abstract

In an integrated nematode management system, the best results are generally obtained by rotating crops with resistant plants, antagonists, or bad hosts of parasites. Some reports indicate that Stylosanthes spp. have the potential to control nematodes. Thus, this study aimed to assess the reaction of Stylosanthes spp. 'Campo Grande' to Pratylenchus brachyurus and Meloidogyne javanica penetration and reproduction at different inoculum levels and examine the histopathology and histochemistry of parasitized plants. Stylosanthes did not prevent P. brachyurus penetration in roots. However, the number of penetrated nematodes was lower than that in soybean from 17 days after inoculation onwards. The numbers of second-stage and third-/fourth-stage juveniles of M. javanica in Stylosanthes roots were close to zero, and no females were observed. Assays conducted using increasing levels of inoculum (P. brachyurus or M. javanica) showed that Stylosanthes was resistant to parasites, with a maximum reproduction factor of 0.59 for P. brachyurus and 0.07 for M. javanica. Histopathological analysis showed the presence of P. brachyurus in Stylosanthes, but without rupture of plant cells. M. javanica individuals were not observed. Histochemistry revealed the presence of phenolic compounds in the epidermis of Stylosanthes and proteins in plant cells. These results show that Stylosanthes spp. 'Campo Grande' can be used in crop rotation programs in fields with mixed infestation of P. brachyurus and M. javanica.