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