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R.Pieters<br />
Malic acid is known to have an effect on the germination of Ascochyta spores.<br />
This acid is produced in the glandular hairs 'on the leaves. The correlation of<br />
hair density with resistance is probably caused by the increased concentration<br />
of malic acid on leaf surfaces with many hairs.<br />
T.S.Sandhu<br />
Are there any techniques available with which we can deal both with vertical<br />
and horizontal resistance at the same time in our breeding program, as vertical<br />
resistance masks the expression of horizontal resistance?<br />
R.Pieters<br />
I know of no method to assess the level of horizontal resistance in the presence<br />
of active vertical resistance.<br />
M.V.Reddy<br />
In order to identify the most relevant criteria, we are looking into the various<br />
disease reactions of the lines found resistant across locations which are supposed<br />
to have HR, and we hope to come up with a criterion or a set of criteria<br />
related with HR.<br />
G.C.Hawtin<br />
In the data you presented two of the parents were fairly highly resistant. How<br />
can you then separate vertical from horizontal resistance in the subsequent<br />
generations following crossing between these resistant lines?<br />
R.Pieters<br />
To avoid introduction of vertical resistance genes a variety will only be accepted<br />
as parent when it possesses following resistance characteristics: (i) quantitativity,<br />
(<strong>ii</strong>) no gene for gene action, and (<strong>ii</strong>i) effect on the develoment of<br />
epidemic. Selections resulting from crosses between approved parents are<br />
checked for above mentioned characteristics again. On top of that, number of<br />
their resistance genes is estimated by crossing with an ultimate susceptible.<br />
The chance that vertical resistance will not be detected and eliminated in the<br />
described process seems to be small.<br />
G.C.Hawtin<br />
From your data and presentation I got the impression that you consider more<br />
than one locus to be involved in resistance. Can you comment further on this<br />
please?<br />
R.Pieters<br />
There is evidence that indeed more loci involving resistance exist. Specific<br />
crossing programs are carried out at the moment to identify these loci.<br />
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