The inheritance of resistance to ascochyta blight in
lentil (Lens culinaris Medik.) caused by Ascochyta fabae Speg.
f. sp. lentis Gossen et al (Syn. A. lentis Vassil.) was
studied using as parents the Canadian cultivars Eston
(susceptible) and Laird (moderately resistant) and two
resistant lines from ICARDA, ILL-5588 and ILL-5684. The F2,
F2-derived Fa families and F2-derived F4 families of each cross
were evaluated for ascochyta resistance under field conditions
in an ascochyta nursery during 1987, 1988 and 1989,
respectively. The parents and segregating populations were
rated for ascochyta reaction on the basis of foliage symptoms,
using a 1 to 9 disease rating scale, with plants rated 1 to
5 considered resistant and plants rated 7 to 9 considered
susceptible. In addition percent seed-borne ascochyta
infection was evaluated, using the seed plating technique.
The cuItivar Eston was susceptible. Laird lentil was
resistant to foliar infection by ascochyta, but its resistance
breaks down in the late podding stage and under the wet
conditions of the ascochyta nursery percent seed-borne
ascochyta infection was even higher than in the susceptible
cultivar Eston. The lines ILL-5588 and ILL-5684 were highly
resistant with resistance persisting after maturity and the
seed coats do not become infected and discolor materially even
with prolonged exposure to wet weather at harvest.
A chi-square test for goodness-of-fit of the F2 and F2-
derived F3 families indicated that resistance to foliar
infection by ascochyta in Laird lentil was conditioned by a
single recessive gene, ral1• Results also indicated that the
resistance to foliage and seed infection by ascochyta of ILL-
5588 and ILL-5684 was due to two - dominant genes,' Ral2 and
Ral3. ILL-5588, but not ILL-5684, also carried the ral1 gene
for resistance to foliar infection by ascochyta and is the
better source of resistance to ascochyta. The high
correlation between percent seed-borne ascochyta infection in
Fz-derived F3 families and in F2-derived F4 families plus the
medium to high heritability estimates (0.52 to 0.8l) indicate
that it will be easy to select for ascochyta resistance in
these crosses.
An effective method of selecting for ascochyta resistance
in lentil was developed. An ascochyta nursery is developed
by spreading infected lentil straw between the lentil rows
prior to flowering. This nursery is then sprinkled
intermittently once or twice each day until about two weeks
after maturity. The crop is permitted to dry naturally and
selections made for ascochyta resistant F2 plants or
replicated progeny rows in later generations. Ascochyta
resistance is based on a low level of discolored seed (0 to
5%), reconfirmed by plating the seed to determine percent
seed-borne ascochyta infection in replicated progeny rows.
Only a few selections have a high level of clean bright seed
and require seed planting. This technique is quick, easy,
effective and efficient. Resulting selections are resistant
to both foliar infection and seed infection by ascochyta.
| Identifer | oai:union.ndltd.org:USASK/oai:ecommons.usask.ca:10388/6887 |
| Date | January 1989 |
| Source Sets | University of Saskatchewan Library |
| Detected Language | English |
| Type | Thesis |
Page generated in 0.0014 seconds