ABACA Activities in the Philippines - Unido

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Ref. No. CFC/FIGHF/09 CFC/UNIDO/FIDA 42 4.3.1 For the bunchy-top trial In Albay, results of the screening trial showed that all the varieties had very low disease incidence during the first nine (9) months and slowly increased 14 months after. Tangongon has the highest disease incidence followed by Lausigon and Laguis. Maguindanao was the last variety which succumbed to the disease and had the least AUDPC while the rest of the varieties exhibited varying degrees of infection. The growth stage of the abaca plant was severely affected by bunchy-top infection as shown by the delayed sword sucker stage on the 9 th month instead of maiden to palm sucker stage (Fig 10). Fig 10. Disease progress curve of bunchy-top infection on eight selected varieties 31 MAP screened in Albay In Davao, although eight (8) varieties were planted in Bago-Oshiro, survival rate of the Bicol varieties were low which resulted to high mortality. Thus, the trial proceeded with six varities only namely, Linawaan, Laguis, Inosa, Maguindanao, Tangongon and Musa tex 51. Unlike in Albay, the eight varieties varied in their reaction to bunchy-top disease. Symptom appearance was delayed for almost nine months from which disease incidence occurred only on the 14 th month. However, the infection in Davao was almost similar to Albay with Musa Tex 51 having 41.35% infection while Tangongon in Albay had 45.66% (Fig. 11). Fig. 11. Disease progress curve of bunchy-top infection on six (6) selected varieties screened in Davao Incidence of bunchy-top on eight (8) varieties and the factors which contributed to the severity of infection 31 months after planting were analyzed with regression analysis. Computed r 2 for the factors which determined percent disease incidence such as infection rate, AUDPC, incubation time in both location were
Ref. No. CFC/FIGHF/09 CFC/UNIDO/FIDA 43 significant contributing 69.82% and 89.86% in Albay and Davao, respectively. High correlation of 83.56 % and 94.79% between the three factors and disease incidence in both locations were also observed (Table 6). Table 6. Regression statistics for the factors involved in the development of bunchy-top disease in selected abaca varieties in Albay and Davao Parameter estimates Albay Davao Multiple R 0.8356 0.9479 R square 0.6982 0.8986 Intercept -20.1893 5.8687 Incubation period 0.0800 -0.0704 Infection rate 247.7716 85.8492 AUDPC 0.0441 0.0505 Observations 31 24 To assess the direct and indirect contributions of multiple, often correlated factors such as infection rate, AUDPC and incubation time on disease incidence, correlation analysis was done which indicated colinearity among predictors which is expressed in the equation Yƒ = a + bx 1 + b x 2 + bx 3 where Yƒ represents disease incidence of the variety, a is regression coefficient; bx 1 is mean incubation time after after emergence; bx 2 is mean infection rate after 30 months after planting; and bx 3 is mean AUDPC after 30 months after planting. The results were used to rank the varieties for their degree of resistance. In Albay, Maguindanao, Inosa and Abuab ranked 1 st , 2 nd and 3 rd respectively, in their degree of resistance to the bunchy-top infection while Maguindanao, Laguis and Linawaan ranked 1 st , 2 nd and 3 rd in Davao (Table 7 & 8). Table 7. Selection of varieties for degree of resistance to bunchy-top disease in Albay Variety Intercep t X 1 Mean Incubation X 2 Mean Infectio n rate X 3 Mean AUDPC Lausigon 0.08 40 247.77 0.1716 0.0441 494.805 - 3.2 42.517 20.1893 4 Abuab 0.08 25 247.77 0.1259 0.0441 343.71 - 31.194 20.1893 2 MT51 0.08 17 247.77 0.1091 0.0441 533.74 - 20.1893 Inosa 0.08 27 247.77 0.0933 0.0441 433.32 - 23.116 20.1893 9 Laguis 0.08 19 247.77 0.1618 0.0441 487.69 - 40.089 20.1893 2 Linawaan 0.08 23 247.77 0.1198 0.0441 422.63 - 29.682 20.1893 8 Tangongon 0.08 36.75 247.77 0.1082 0.0441 707.98 - 26.808 20.1893 7 21.8209 47.3489 8 15.1576 28.1625 3 27.031 23.5379 31.7403 5 19.1094 24.1970 2 21.5071 42.9270 7 18.637 29.9715 4 31.2219 40.7813 6 Maguindanao 0.08 33.5 247.77 0.0897 0.0441 342.87 - 20.1893 22.237 3 15.1205 19.8486 1 Y Ran k
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ABACA Activities in the Philippines - Unido

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