A comprehensive investigation into Meloidogyne graminicola in Bangladesh: systematic survey, pathogenicity assessment and screening for resistant varieties

Summary Between December 2020 and March 2021, an extensive survey was conducted across Bangladesh to determine the prevalence of root-knot nematode ( Meloidogyne graminicola ) infestation in rice ( Oryza sativa ) nursery fields. This survey involved collecting 29 nematode populations from 29 distinct Agro-ecological zones (AEZs). Disease incidence and severity were assessed using the root-knot index. Results indicated a wide variation in the incidence of rice root-knot disease, ranging from 10 to 100% across the surveyed locations. Notably, the highest incidence of 100% was recorded in AEZ 30 followed by AEZ 3 (88.33%) and AEZ 9 (83%). By contrast, the lowest incidence was found in AEZ 17 (10%), with other low-incidence zones including AEZ 18 (20%), AEZ 13 (22.33%) and AEZ 6 (23%). A pathogenicity test was conducted on 29 M. graminicola populations isolated from the 29 AEZs to evaluate their virulence on the rice cultivar ‘Nipponbare’. Among these populations, based on pathogenicity, 25 exhibited high aggressiveness, three were mildly aggressive, and one was found to be weakly aggressive. Additionally, a varietal screening experiment was conducted to assess the susceptibility of various genotypes collected from Bangladesh under laboratory conditions. Out of 28 genotypes tested, ‘Shishumati’, ‘BRRIdhan 49’ and ‘Binni’ demonstrated moderate resistance. Nine genotypes were classified as susceptible, while 16 were categorised as moderately susceptible. This comprehensive survey provides critical insights into the distribution and severity of M. graminicola infestations in rice fields in Bangladesh. Knowledge of virulent root-knot nematode populations and the identification of resistant rice varieties will greatly aid in developing effective management strategies to combat this nematode infestation.