I - --ii

58
5 Stem lesions common, 2 to 6 mm long/or 5.1 to 25%
foliage infection (moderately susceptible)
7 Stem lesions very common, bigger than 6 mm and/or 25.1
to 75% foliage infection (susceptible)
9 Stem lesions extensive, all young shoots and/or leaves
killed (highly susceptible)
The data on disease grades produced by 13 isolates of A. rabiei on 14 cultivars
are given in Table 2. It is evident that all isolates produced disease grades 7 and 9
on cultivars B-98, Attock, BN 3118, GC Bijapur, NP 100 and Pb 7 indicating
that they are susceptible to A. rabiei. The remaining eight cultivars showed
differential disease reaction to various isolates.
In order to illustrate the point of physiologic specialization or races in A.
rabiei, the results obtained have been summarized in Table 3. The fast-growing
and less-sporulating isolates G-3 1,G-5 1,G-52, R-2 1,L-24 and L-60 forming race
1produced disease grades I and 3 on cultivars 1-31, EC 26435 and C 235. On the
other hand, the slow-growing, more-sporulating isolates L-I, L- 11, G-5, G-20, G­
32 and D-30 forming race 2 produced disease grades 5 and 7 on the above three
cultivars. Isolate J 101 giving disease grade 3 on cultivars 1-13 and C 235 and
grade 5 on EC 26435 was designated as biotype of race 2. Race 2 appears to be a
new race because the old resistant cultivar C 235 is susceptible to this race.
In order to locate more sources of resistance,well known blight-resistant lines
and cultivars such as C 727 from Pakistan (Aziz 1962), "Bulgarian" from Israel
(Solel and Kostrinski 1964), two hybrids VIR 32 and K 279 from USSR (Vedysheva
1966), line 12-074-06625 (1-13) from Iran (Kaiser 1972), lines EC 26414,
EC 26435 and EC 26446 from Israel, Galben Cafai from Rumania and V 138
from Mexico (Sandhu 1972) were screened for resistance to more virulent race 2
of A. rabiei at New Delhi under artificial epipytotic conditions (irewal and Vir
1974). The data are given in Table 4. All genotypes except 1528-1-1 were found
to be moderately susceptible to susceptible (disease grades 5 and 7) to race 2 of
A. rabiei. Line 1528-1-1 from Morocco, however, did not get infected even with
race 2 and was therefore graded as highly resistant.
Discussion
Luthra et al. (1939) reported cultural and morphological variations among six
isolates of A. rabiei. In the present study, 268 isolates of A. rabiei were grouped
into 13 forms. One representative each of the 13 forms was used in further
studies. Relatively fast-growing and less sporulating isolates, G-31, G-51, G-52,
R-21, L-24 and L-60, were less virulent. On the other hand, slow-growing and
abundantly-sporulating isolates, J-101, D-30, L-1, L-1 1, G-5, G-20, G-32 and D­
30, were more virulent. Kaiser (1973) reported that isolates of A. rabiei from