Rice tungro disease management - IRRI books - International Rice ...

Fig. 2. Distinct rice tungro bacilliform virus (RTBV) genotypes detected in the Philippines. Genotypes1-9 were initially found in lsabela while genotypes 10-24 were initially found in North Cotabato. Lanemarked M is a DNA size marker from the RTBV-lc3 clone.RTBV mixed infections (based on the total number of DNA fragments detected>16 kb) were common and accounted tor 10–54% of the total sample population.During the 1997 DS, their frequency was even higher than for a single infection inNorth Cotabato (Fig. 3, Table 1).Based on the frequency of the genotypes using Pearson’s correlation coefficient,RTBV genotypes were distributed geographically (Fig. 4). This showed that the genotypefrequencies between Isabela and North Cotabato were significantly different. InIsabela, 10 distinct genotypes (1, 2, 3, 5, 9, 11, 17, 16, 19, and 35) were identifiedduring the 1996 WS and in the 1997 WS. Only five genotypes (3, 5, 9, 19, and 25)were identical to those detected earlier from the same province. Genotypes 3 and 5generally dominated in the 1996 WS, but these genotypes were augmented with genotypes9 and 25 in the 1997 WS. A similar pattern was observed in North Cotabatoduring the 1997 DS and WS. In the 1997 DS, 13 distinct genotypes were observed (2,3, 10–16, 18–20, and 24) and, in the following season (1997 WS), 11 genotypes wereidentified (10–16, 18–20, and 24). Genotypes 10–13 were the most frequent in the1997 DS and remained dominant in the 1997 WS.Preliminary analysis 13