Evaluation of the host response of lowland and upland rice varieties from Myanmar to the rice root-knot nematode Meloidogyne graminicola

Abstract

The rice root-knot nematode Meloidogyne graminicola is considered one of the most potentially important nematode pathogens of rice, especially in South and Southeast Asia, in a range of rice production systems. Identification of M. graminicola-resistant or -tolerant rice varieties will enable breeding programmes to develop rice varieties which are able to limit yield losses caused by this nematode species. The host response to M. graminicola infection of 15 lowland rice varieties and 9 upland rice varieties, which are being grown in the summer-irrigated lowland and rainfed upland rice ecosystems in Myanmar, was evaluated in two experiments under screenhouse conditions. The lowland rice experiment was carried out under intermittently flooded conditions in a clay loam soil (i.e. simulating the summer-irrigated lowland rice ecosystem) and the upland rice experiment was carried out at field capacity in a sandy loam soil (i.e. simulating the monsoon rainfed upland rice ecosystem). None of the15 lowland and 9 upland rice varieties were resistant to M. graminicola infection although differences in susceptibility and sensitivity were observed. Six (or 40%) out of the 15 lowland varieties examined were classified as less susceptible (LS) to M. graminicola infection, five (or 33.3%) as moderately susceptible (MS) while four (or 26.7%) as highly susceptible (HS). One (or 11.1%) out of the nine upland varieties examined was classified as LS to M. graminicola infection, three (or 33.3%) as MS while five (or 55.6%) as HS. Five (or 33.3%) out of the 15 lowland varieties examined were classified as either less sensitive or tolerant to M. graminicola infection. One (or 11.1%) out of the nine upland varieties examined was classified as tolerant to M. graminicola infection. This study offers interesting information for the farmer regarding which rice variety should be grown in M. graminicola-infested fields under either lowland or upland conditions.

Keywords:

• ecosystem
• gall rating
• lowland rice
• nematode reproduction
• Oryza sativa
• plant growth
• resistance
• sensitive
• susceptible
• tolerance
• upland rice

Acknowledgements

This study was supported by a Flemish Interuniversity Council (VLIR-UOS) PhD scholarship to Win PP. The authors express appreciation to the Plant Protection Division (Yangon), Myanmar Rice Research Centre (Hmawbi), Rice Division, Department of Agricultural Research (Yezin) and Aung Ban Research Farm (Shan State) of the Ministry of Agriculture and Irrigation, Myanmar for the facilities and assistance in conducting the experiments.

Notes

1. In the averages of the upland rice varieties, the values of the lowland variety Thihtatyin have been included because this variety was also grown under rainfed upland conditions in the second experiment. We have compared the averages of the upland varieties with and without the values of the variety Thihtatyin and the averages were very similar with the exception of the average reduction in fresh root weight which was higher when the variety Thihtatyin was not included (43 vs. 30.8%).