Incidence of Root-Knot of Rice at the Nursery and Maturing Stages in Some Districts of Uttar Pradesh

Surveys conducted in rice fields revealed highest frequency of occurrence and disease incidence of root-knot caused by Meloidogyne graminicola in Atrauli block (41.7 and 42.4%, respectively), and the lowest in Tappal block (Tehsil or block) (15.3 and 27.8%, respectively) at the nursery stage (1-2 weeks after transplanting). At maturity stage, Atrauli block also recorded both the parameters highest (56.2%, and 61.3%, respectively), followed by Chandaus (54.1 and 58.4%) and Iglas (52.8 and 57.6%, respectively) blocks. Disease severity was relatively higher in Aligarh district, where Atrauli block recorded the maximum root gall and egg mass indices during nursery stage (8.2 and 4.0, respectively), while at maturity stage the indices were recorded highest in Atrauli block (8.2 and 6.3, respectively). In Bulandshahr district, nursery-stage observations revealed the highest frequency of occurrence and disease incidence in Anoopshahar block (25.4 and 30.2%, respectively), whereas lowest in the Khurja block (17.9 and 21.9%, respectively). At maturity stage, the two parameters were found highest in Anoopshahar block (42.1 and 44.1%, respectively). Root gall severity and egg mass production remained lower in Bulandshahr district than Aligarh district, and the highest indices were observed in Anoopshahar block (7.1 and 6.0, respectively) at the maturity stage. The highest relative yield loss was recorded in Aligarh district (57.5%) with considerable variation among blocks (40-58%), whereas comparatively lower yield losses were recorded in Bulandshahr district (42.0%). The soil population of M. graminicola juveniles was substantially higher in Aligarh district compared to Bulandshahr district at both crop stages, and showed positive relationship with disease incidence and root gall severity.