Screening Napier grass accessions for resistance to Napier grass stunt disease using the loop-mediated isothermal amplification of DNA (LAMP)

Napier grass stunt (NGS) disease is a major threat to Napier grass cultivation and the smallholder dairy industry in East and Central Africa. The disease is caused by a phytoplasma, which is transmitted by the leafhopper Maiestas banda (Kramer) (Hemiptera: Cicadellidae). The current study was conducted to identify among 65 Napier grass accessions that could be resistant to NGS disease using the loop-mediated isothermal amplification of DNA (LAMP). The accessions were caged with NGS phytoplasma-infected Napier grass as inoculum source and M. banda as the vector. All Napier grass accessions were subjected to phytoplasma testing thereafter 18 phytoplasma negative and five asymptomatic accessions were selected and used in further screening by subjecting the extracted DNA to LAMP. Plant response to the NGS phytoplasma by symptom expression, impact on yield-related parameters and phytoplasma infection was used to evaluate tolerance or resistance over a period of three months. Most Napier grass accessions were susceptible to the disease except plants belonging to accession 16789 which were negative by LAMP. Napier grass accession 16807 was found to be tolerant with 60% plants positive by LAMP and 90% plants symptomless. Accessions 16822 and 16817 had moderate tolerance with one and two plants positive by LAMP, respectively. Accession 16812 was slightly tolerant with 58.3% plants positive by LAMP and 33.3% of the plants showing symptom remission in the second re-growth. This study indicates there could be resistance and tolerance to NGS disease which could be exploited in the development of an integrated management strategy for this disease.