ABACA Activities in the Philippines - Unido

Ref. No. CFC/FIGHF/09 CFC/UNIDO/FIDA 34
1. Fiber yield, biomass – measured by weight per unit area
2. Loss in yield as a measure of host resistance – estimated based on a control which could be obtained
from agronomic evaluation trial. Compute losses in yield due to diseases. Use the equation, %
Loss = (Yield of healthy plants - yield of diseased plants)/ Yield of healthy plants x 100. Yield of
healthy plants can be from agronomic trials. Loss is an indication of tolerance. When two
varieties have the same amount of disease but different losses in yield, it means that the one with
the lower loss is more tolerant/resistant.
Analysis of data
Disease incidence on the selected varieties were observed through qualitative description of the kind
of symptoms manifested on 20 samples in each replication from the time of planting. The percentage disease
incidence were statistically analyzed particularly analysis of variance (ANOVA) to compare possible
tolerance/resistance of the varieties. The rate of disease development and areas under the disease progress
curve to determine quantitative differences brought about by the different types of resistance was also done
and to ascertain the relationship between disease incidence and plant growth development, regression and
correlation analyses were undertaken. The regressions were performed on means of infection rate, AUDPC,
incubation time over four replications with the disease incidence as the dependent variable. Regression
model with predetermined combination of predictors was tested. The resulting equation:
Y disease incidence = a + b x 1 + b x 2 + b x 3
where
a = intercept or constant
b = coefficient value
x 1 = mean incubation period
x 2 = mean infection rate
x 3 = mean AUDPC
The resulting analysis was assessed by aptness of residual plot, coefficient of determination and F test.
Multiple regression analysis was also done to determine the effect of independent variables (incubation time,
infection rate and AUDPC) on the expression of the disease (bunchy-top and mosaic) manifested on the eight
varieties. Yield loss relative to the degree of host tolerance to the virus was also analyzed.
Ranking of entries
Resistance analysis was used to rate the varieties. Lower infection rate, smaller AUDPC, flatter
disease progress curve, longer incubation time were considered as the criteria in evaluating varieties for
resistance. When resistance was observed, it was considered as the primary parameter in varietal selection.
The varieties were evaluated based on a Selection Index = ƒ(fiber yield, Y disease incidence ) where resistance to the
viruses and good agronomic characteristics are given relative weights. Since viral diseases constitute the
current problem, more weights were put on resistance.
4. Results and Discussion
4.1 Result of evaluation of varieties used for the regional screening
There are about 200 abaca varieties/accessions widely planted in the different parts of the
country in Luzon, Visayas and Mindanao where the prevailing conditions suit abaca production.
These varieties are characterized and maintained in FIDA seedbanks and experiment stations in
Sorsogon (Luzon varieties), Leyte (Visayas varieties) and Davao City (Mindanao varieties). Same
germplasm are kept in genebank collection of the National Abaca Research Center in Leyte State
University and Abaca Seedbank Collection in the College of Forestry, University of the Philippines
Los Baños (UPLB). Together with a plant breeder from the Institute of Plant Breeding in UPLB,
primary data on the agronomic characteristics of the varieties/accessions generated by FIDA
seedbanks were used to select varieties used for the regional screening. Among the collection, 40