Evaluation of the response of rice genotypes to bacterial leaf streak disease in Uganda

Abstract

Destructive rice diseases like bacterial leaf streak (Xanthomonas oryzae pv. oryzicola) have been reported to be on the increase. In 2014, researchers in Uganda spotted signs typical of bacterial leaf streak disease (BLS) in rice fields in Butalejja, Namutumba, and Iganga districts in Eastern Uganda. Bacterial leaf streak is one of the devastating diseases of rice in subtropical Asia and parts of Africa, causing yield loss of up to 60% in susceptible varieties. Host plant resistance has been suggested as the most effective way of managing the disease. However, the reaction of rice genotypes to the disease in Uganda is not yet known. A study was conducted with the objective of identifying sources of resistance to bacterial leaf streak disease in Uganda. Thirty five rice genotypes were evaluated for their reaction to the disease using a BLS isolate (BLS 78) collected from Namulonge in Wakiso district in Central Uganda using the infiltration method with a needleless syringe. Inoculation was done at 30 days after planting and data collected 15 days after inoculation. Data was collected on the streak length induced by BLS on the inoculated leaves. The mean streak length per rice genotype was interpreted as; Resistant (R), 0 < SL ≤ 1mm, Moderately Resistant (MR), 1 < SL ≤ 10mm, Moderately Susceptible (MS), 10 < SL ≤ 30 mm, Susceptible (S) SL > 30mm. The mean streak length due to BLS varied signficantly (p<0.001) among the genotypes. The observations ranged from highly resistant in Nerica1, Nerica 6 and IURON plot 7 to highly susceptible in Du 363. Only three genotypes were found to be resistant, eight were moderately resistant, 11 were moderately susceptible while 12 were found to be susceptible. The resistant genotypes identified could be used as sources of genes for introgression into susceptible but agronomically desirable rice genotypes in the country.