Histopathological changes caused by Heterodera sacchari in NERICA 1 rice roots

摘要

The cyst nematodes (Heterodera spp.) are particularly damaging group of pests on a wide range of crops. Heterodera sacchari is an important nematode of rice {Oryza spp.) causing significant damage and yield loss in rice. This study was initiated withthe major objective of understanding the histopathological changes caused by H. sacchari on susceptible NERICA 1 rice cultivar. Three-week old seedlings of NERICA 1 rice were inoculated with 5000 second-stage juveniles of H. sacchari and roots were obtained from rice at 7, 14, 21 and 24 days after inoculation (DAI). Infected roots were rinsed with tap water and fixed in formalin-propiono-propanol. Fixed roots were dehydrated in graded isopropyl alcohol series. Roots were infiltrated with paraffin wax and embedded in molten paraplast. Root sections of 14 )am were cut with a rotary microtome and photomicrographs were taken. Infective second-stage juveniles of H. sacchari penetrated, developed and established multinucleate syncytia seven DAI. The number of syncytia observed near the head of each nematode ranged from two to seven. Extensive root damage and disorganization of epidermal, cortical and vascular elements occurred 14 and 21 DAI. Severe root cracks occurred and aggregation of matured white females along the root axis were observed 21 DAI. Large numbers of embryonated eggs were observed inside the females with extensive destruction of roots 24 DAI. Syncytia were observed in both cortical and vascular regions of the root.