Developing crop descriptor lists - Bioversity International

18 BIOVERSITY INTERNATIONAL TECHNICAL BULLETIN SERIES NO. 13
Observation of these descriptors may involve the use of simple to
complex techniques and equipment.
To score evaluation descriptors, it is often necessary to use
appropriate experimental designs and statistical analyses trials
that are much more complex and resource intensive than is
necessary for characterization. Since evaluation descriptors
are influenced by environmental conditions, curators, breeders
and researchers conduct replicated trials over years to obtain
objective results for these traits. Evaluation is generally carried
out as part of a breeding programme and in collaboration with
other crop improvement scientists, such as pathologists and
entomologists, and also with farmers (various participatory
methods of crop improvement), where germplasm undergo
evaluation for specific traits. Ideally, these results are then
fed back to the originating genebank in order to complement
existing data.
Descriptors listed under biotic stress susceptibilities (pests and
diseases) should include both specific and common names.
Example #16
Fungi
Alternaria sesami Leaf spot and blight
Cercospora sesami Leaf spot
Colletotrichum spp. Anthracnose
Recently published descriptor lists are comprehensive, with
asterisked characterization and evaluation descriptors indicating
the minimum set of highly discriminating characteristics that
should be recorded for each accession. Asterisked descriptors are
particularly useful indicators of diversity in collections and for
international harmonization of documentation systems.
4. Similarities to and differences from other
technical guidelines
Over the years, different guidelines for plant genetic resources
documentation have been developed by UPOV, COMECON, USDA-
GRIN and others, in addition to those developed by Bioversity and
its predecessors. In addition, several national programmes have been
developing descriptors for crops of national interest and for which
internationally accepted lists were not available. Below is a short
summary and description of the more commonly used descriptor
lists.