I - --ii

Table 3
Disease rating in F 2 populations initiated for development
of cultivars with horizontal resistance at Tel Hadya, 1980-81.
Cross/Parents Total No. of plant.; with rating of
plants I 2 3 4 5 6 7 8 9
103
ILC 1919 P1 45 0 0 0 0 12 13 17 0 3
(ILC 1919 X ILC 2582) F2 812 0 0 0 3 69 220 367 69 84
ILC 2589 P2 13 0 0 0 0 4 3 I 3 2
ILC 1919 P1 4-t 0 0 0 0 2 11 19 6 6
(ILC 1919 X ILC 215) F2 304 0 0 0 1 14 59 108 84 38
1LC215 P2 51 0 0 0 0 3 12 29 5 2
1LC 249 P1 42 0 0 0 0 9 16 15 1 I
(ILC 249 X ILC 1919) F2 633 0 0 12 24 189 203 168 20 17
ILC 1919 P2 28 0 0 0 0 3 4 13 4 4
P 1
1LC 215 47 0 0 0 0 5 9 22 9 2
(ILC 215 X ILC 190) F 2 496 0 0 11 8 42 116 165 88 66
ILC 190 P 2 45 0 0 0 0 7 12 21 0 5
main season in the disease nursery and the crosses indicated above will be
repeated. This process will be repeated until a high level of resistance is achieved.
At that stage individual plants will be selected and tested for uniformity, seed
yield and other agronomic traits. These lines will then be made available to
cooperators working in similar ecological zones for selection in local conditions
and for use in breeding programs.
Multilines
In 1952, Jensen proposed that a multiline cultivar in oats might be produced
through the blending of seed of several compatible pure lines. Later Borlaug and
Gibler (1953) and Borlaug (1959) reported the use of a modified backcross
technique in developing a wheat multiline incorporating a number of different
resistance genes in a single genotype. 'Miramaer 63' was the first multiline wheat
cultivar released for commercial cultivation in Columbia (Anon. 1963). Frey et
al.(1977) have released 11 multiline oat cultivars for commercial cultivation in
the Corn Belt of the USA. Tumult, a multiline wheat cultivar, was released in
1977 in the Netherlands (Groenewegen 1977). Recently CIMMYT and Indian
programs have developed a number of multiline cultivars in wheat (Rajarsm et
al. 1979; Gill et al.1979; Luthra and Rao 1979). Theoretically the life expectancy
of a multiline should be longer than that of a pure line because it is very
unlikely that a virulent race may appear which can overcome all the resistance
components of a multiline cultivar. The disadvantages of the classical multiline
are many. The major one is that there is no gain in yield over the recurrent parent