ABACA Activities in the Philippines - Unido

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Ref. No. CFC/FIGHF/09 CFC/UNIDO/FIDA 38 Fig. 5. Typical symptoms of the abaca mosaic disease in Albay The mosaic trial for Luzon varieties was also held in Tabiguian, Tabaco, Albay since the location is also identified as a hotspot for abaca and bract mosaic diseases. Results of screening of five varieties (Musa tex 50, Musa tex 51, Musa tex 52, Lausigon and Abuab) for resistance to mosaic as shown by disease progress curve indicated Lausigon having the lowest percentage of infection and flatter curve while Musa tex 50 had the highest percentage of infection (Fig 6). With regards to infection rate, AUDPC and disease incidence, Abuab, Lausigon and Musa tex 51 ranked 1, 2 and 3 interchangeably (Table 3). Fig 6. Disease progress curve of the mosaic infection in Albay Based on overall ranking of Luzon varieties with regard to their reaction to abaca mosaic and bract mosaic diseases, the top three varieties are Lausigon, Abuab and Musa tex 51. Table 3. Selection of top three Luzon abaca varieties grown in Albay based on their reaction to abaca mosaic and bract mosaic diseases VARIETIES INFECTION RATE AUDPC DISEASE INCIDENCE(%) OVER-ALL RANKING Musa tex 50 Musa tex 51 Musa tex 52 Lausigon Abuab 0.4149 (5) -0.3317 (3) 0.0206 (4) -0.4030 (1) -0.3279 (2) 120.8470 (5) 32.5200 (3) 41.0940 (4) 30.0000 (2) 29.1600 (1) 36.3 (5) 11.4 (2) 15.2 (4) 8.9 (1) 12.3 (3) 15 (5) 8 (3) 12 (4) 4 (1) 6 (2)
Ref. No. CFC/FIGHF/09 CFC/UNIDO/FIDA 39 4.2.2b Leyte In the Visayas, field screening of sixteen (16) abaca varieties for abaca mosaic resistance was conducted in Barangay Liberty in Hilongos, Leyte from April to December 1999. But frequent flooding occurred in the area causing high mortality in some experimental plants which resulted to high variability in observations among the varieties as reflected in the 44.32% coefficient of variation although replanting was done. The results were found unreliable, thus, the conduct of another trial was recommended. Due to time constraint, a greenhouse screening was undertaken on varieties which showed possible resistance to the disease. Among the 16 varieties, the following seven varieties were chosen for the pot experiment; Musa Tex 80, Musa Tex 81, Laylay, Laguis, Lagurhuan, Soglagur, and Inosa. However, the planting materials of Musa Tex 81 were not sufficient for the designed experiment, thus Minenonga, which ranked fifth was chosen. The screening was undertaken in March 2000 at EVIRFES, Abuyog, Leyte wherein 30 suckers for each variety were planted in plastic bags kept in a screenhouse. Mosaic-infected plants were, likewise, maintained in a separate screenhouse from which aphid vector of the AbaMV were allowed to feed for transmission of the virus. A protocol was followed in performing virus transmission by aphid and maintenance of the experimental setup from which the number of plants and percent mosaic infection were gathered at four observation dates. To determine the reactions of the varieties to mosaic infection, a measure of their resistance was necessary. This was done through virus-indexing using ELISA of every test plants for each variety. Leaf samples were collected starting at 30 days post-inoculation (dpi) and repeated sampling was done at 45, 60, 75 dpi. Selection of the top three varieties was based on the manifestation of the disease through percent mosaic infection and the results of ELISA through the mean absorbance values read at 405 nm using microplate reader (BIORAD, USA) of the Plant Virology Laboratory of the Department of Plant Pathology in UPLB. In the field screening conducted in Hilongos, Leyte appearance of the initial symptoms such as whitish streaks along leaf veins from midrib of the leaf margin was observed on the third week from planting while in the greenhouse screening, the first symptoms appeared 100 days after inoculation. This explains the relative importance of the inoculum pressure that exist under the natural condition wherein the abaca actually exist. However, symptom appearance in both experiments which appeared in succeeding days were similar. Manifestation of the disease is more pronounced and diverse. In Linawaan, leaf curling was observed while in Lagurhuan, whitish streaks were smaller. In Laylay, white band chlorosis which run across the midrib was evident. In Laguis, yellow to bright orange streaks which run parallel to the vein appeared on younger leaves. Necrotic lesions appeared on petioles in all varieties (Fig. 7). Fig 7. Symptoms of abaca mosaic disease on abaca plants grown in Leyte Results of greenhouse screening and absorbance values obtained by ELISA showed that Inosa, Lagurhuan, Linawaan and Laguis showed degree of resistance to abaca mosaic disease than Laylay, Minenonga and Musa Tex 80 (Table 4). Based on the results of greenhouse experiment, the top three selected Visayan varieties to be included in the national screening are Inosa, Linawaan and Laguis. Lagurhuan was not chosen because it is not commonly planted in the region.
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ABACA Activities in the Philippines - Unido

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