Dynamics of Aphelenchoides besseyi in different rice cultivars

Aphelenchoides besseyi is among the most devastating plant-parasitic nematodes and causes severe loss, mainly on japonica rice in China. Recently the nematode has been found to be present in the seeds of indica rice and the hybrid rice cultivars also show symptoms of the nematode damage. To understand the variations in different rice cultivars against A. besseyi, the dynamics of nematode population, the incidence of symptoms and the effects on plant yield were investigated in field experiments during 2017-2018 by inoculation of mixed stages of A. besseyi onto the seeds and seedlings of different types of rice cultivars. The results showed few nematodes could be recovered from the plants at the seedling and the end of tillering stages in all the cultivars. After flowering, the number of nematodes per panicle increased and the highest number was found in ‘Zheyou 18’ in 2017 (1050.2) and 2018 (732.1). The average incidence of the inoculated plants showing white-tip symptoms ranged from 0.5 to 10.3% and from 0.0 to 75.7% at the tillering stage in 2017 and 2018, respectively. The incidences of white-tip symptoms in the indica cultivars, including ‘9311’, ‘Minghui 63’ and ‘Nei 5 you 39’, were significantly lower than in ‘Xingxiang’, a japonica cultivar and ‘Zheyou 18’, a hybrid rice cultivar, both at the flowering stage in 2017 and at the end of the tillering stage in 2018. A strong interaction of the treatments and cultivars on the 1000-grain weight and panicle length was evident.