Assessing resistance of rubber tree clones to <Emphasis Type="Italic">Microcyclus ulei</Emphasis> in large-scale clone trials in Ecuador: a less time-consuming field method |
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Authors: | Franck Rivano Malena Martinez Victor Cevallos Christian Cilas |
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Institution: | 1.CIRAD, UPR Systèmes de pérennes,Montpellier Cedex 5,France;2.INIAP, Estación Experimental Santo Domingo,La Concordia,Ecuador;3.CIRAD, UPR Bioagresseurs de pérennes,Montpellier Cedex 5,France |
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Abstract: | Resistance of rubber tree clones to South American Leaf Blight (SALB) caused by the fungus Microcyclus ulei is normally assessed in specific large-scale clone trials, which in general entail a considerable amount of work. Four variables
are observed monthly on each tree over many years: disease severity and conidial sporulation intensity on young leaves, and
severity and stroma density on mature leaves. In order to simplify this field assessment method, we tested the resistance
of eight rubber tree clones to M. ulei in Ecuador in a Fisher block design with four replicates per treatment. Three months after planting, monthly observations
were made for a period of 12 months on the foliage focusing on the four variables, in order to quantify disease development.
Given the correlations between the four variables, assessment of conidial sporulation intensity on young leaves and stroma
density on mature leaves should be sufficient. The most suitable period to start the assessment was 6 months after planting,
for a duration of six to nine months. As repeated observations on the same trees were autocorrelated, it was possible to reduce
the assessment frequency to once every 2 months. To conclude, assessing the resistance of rubber tree clones to SALB in large-scale
clone trials can be optimized to reduce the number of observation times by 50%. |
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