Dr Joseph Nsengimana has successfully defended his doctoral thesis entitled “PREVALENCE OF MELOIDOGYNE GRAMINICOLA IN RICE FIELDS IN RWANDA, EFFECT OF PLANT HORMONES AND APPLICATION OF siRNA IN RICE-NEMATODES INTERACTION” before the panel of examiners in Nairobi on 17th May, 2018. The undertaking of this research was motivated by the facts that :
- The intensive monocropping of rice in Rwanda has gradually built up the pressure of pests and diseases to alarming levels in several marshlands where the most common epidemics on rice are blast disease and diopsis pest.
- The status of nematode problems in rice fields in Rwanda has not been investigated so far and previous research works have demonstrated that nematodes are among important pests worldwide.
- Root-knot nematodes (Meloidogyne spp.) are one of the three most economically damaging genera of plant-parasitic nematodes on horticultural and field crops, particularly on rice grown upland and in aerobic fields.
The findings from the survey on prevalence of M. graminicola in Rwanda showed that nematodes are not yet a threat in rice fields as most of nematodes sampled in different marshlands were free-living with few plant parasitic nematodes. However, the infection experiment on cultivars of rice in laboratory revealed that all fifteen (15) tested rice cultivars grown in Rwanda were susceptible to M. graminicola.
The evaluation of the effects of plant hormones revealed that the foliar spray of methyljasmonate and ethylene on rice seedlings significantly conferred resistance of rice against M. graminicola infection. The same is true for salicylic acid. With riboflavin spray, the infected plants continued to grow and were healthy enough despite galls that had developed on roots.
In this research, it was demonstrated that M. graminicola is readily susceptible to siRNAs of
Mg-pat-10 and Mg-unc-87, two genes involved in nematode motility
The research outcome calls on different players viz farmers, Government institutions, researchers and scientific community ;
- To constantly monitor the rice field in marshlands of Rwamagana and Cyili where plant parasitic nematodes were found. This is very important as plant parasitic nematodes can unexpectedly outbreak. The monitoring should also be extended to small rice fields in Rwanda ;
- To promote the cultivation of varieties that has shown less susceptibility to graminicola (NERICA and NERRICA breeded varieties) ;
- To make more effort to produced tolerant/resistant cultivars, which give more yield in addition to resistance to graminicola ;
- To carry further work on the effect of riboflavin so that it can be used as a booster for rice production, by investigating the effect of the uptake through roots ;
- To further investigate on the mechanism of regulation of siRNAs in other to make it more persistent and permanent and also look on novel genes like those involved in nematodes reproduction ;
- To develop scientific work for transgenic rice that would fight itself against graminicola ;
Dr Joseph Nsengimana is a Lecturer in the Department of Biology, College of Science and Technology, University of Rwanda. Special thanks are addressed to the Belgian Technical Cooperation (BTC, CTB) for having financially supported part of the research that was carried out at Ghent University, Belgium.