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taken on potential parents, is being developed to<br />
ensure that the best crosses will be made.<br />
In rainy season 1976, 525 new F 1 's and 1000<br />
F 2 's were grown. The best selections from these<br />
were advanced in the 1977 hot dry season nursery<br />
where 266 superior F 3 's and 126 F 4 's were<br />
identified for the 1977 Uniform Nurseries. The<br />
remaining 1976 selections will be grown in rainy<br />
season 1977.<br />
From more advanced lines, 48 progeniesmostly<br />
of African x Indian parentage - were<br />
chosen after intense selection for tillering (either<br />
one or many synchronous tillers), disease resistance,<br />
seed setting, and yield potential for<br />
entry into 1977 replicated yield trials; these lines,<br />
in nursery form, have also been supplied to 30<br />
breeders in the SAT.<br />
Ninety inbreds were tested in two yield trials at<br />
several locations in 1976. In both trials, a few<br />
inbreds gave yields equal to the hybrid check<br />
PHB 14. In Trial 1, grown at Bambey, Senegal,<br />
and at three Indian locations, three inbreds<br />
showed low levels of downy mildew incidence,<br />
besides yields equal to the check (Table 14). If the<br />
general relationship between inbred and hybrid<br />
yield levels holds true, then good inbred lines per<br />
se can be expected to produce better hybrids or<br />
synthetics. High inbred yield levels are also<br />
desirable in hybrid seed parents.<br />
Three synthetics were generated from good<br />
inbreds and tested in IPMAT-2 (see International<br />
Cooperation) in 1976. One of these<br />
(SYN 7601, composed of six lines) showed some<br />
potential, but will require some refinement<br />
before release because it exhibited more phenotypic<br />
variability than is acceptable.<br />
Hybrids<br />
Three systems of cytoplasmic male sterility are<br />
being used to produce high-yielding diseaseresistant<br />
hybrids.<br />
Potential hybrid parents are developed in both<br />
the Variety Cross and Population Improvement<br />
projects and pass through three stages. Initially<br />
test-crosses are evaluated in single plots at<br />
ICRISAT Center, where most have to be discarded<br />
because of incomplete pollen shedding.<br />
Agronomically satisfactory fertile crosses move<br />
to the second stage —a replicated trial at several<br />
locations, including the DM nursery. Those<br />
surviving reach the third stage of wider national<br />
and international testing (Fig 20).<br />
Table 14. Grain yields and downy mildew incidence of selected inbreds in P M I T 1,1976.<br />
Grain yield<br />
Increase<br />
ICRISAT Bambey,<br />
above<br />
Center a Senegal Mean b PHB-14<br />
DM incidence<br />
ICRISAT<br />
Center<br />
Bambey,<br />
Senegal<br />
(kg/ha)<br />
(%) (%) (%)<br />
Souna D 2 x Ex-Bornu-161<br />
T 166-2 x 700594<br />
700638 xSC3(M)-17-1-2<br />
PHB 14 c<br />
Mean (46 entries)<br />
L.S.D. (0.05)<br />
3675<br />
3184<br />
3647<br />
3475<br />
2424<br />
±396<br />
1110<br />
2190<br />
2507<br />
1853<br />
1657<br />
1619<br />
±2 6 2<br />
735<br />
2649<br />
2344<br />
2264<br />
2220<br />
1671<br />
±330<br />
752<br />
19<br />
6<br />
2<br />
-<br />
- 2 5<br />
1.6 0.0<br />
1.4 11.3<br />
1.4 1.3<br />
2.5 13.7<br />
NA d N A<br />
a The plots at ICRISAT Center had received 80 kg P 2 O 5 and 150 kg N per ha.<br />
b Mean yield over four locations.<br />
c Highest-yielding check.<br />
d Not averaged.<br />
55
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