RA 00048.pdf - OAR@ICRISAT

Table 3.
Mean 1000-seed weights of P - 7 2 1 opaque and its normal sib line during grain development in a
space planted population.
1000-seed dry weight (g) a
Days after P-721 P-721 % P-721 opaque
pollination normal opaque of normal
17 7.625 7.875 103.3
24 14.664 14.294 97.5
31 18.562 18.998 97.7
38 23.164 21.652 93.5
45 25.455 21.608 84.9
52 24.099 21.451 89.0
59 24.861 21.358 85.9
a Mean of three replicates.
without attention to chemical evaluation because
the major objective was to derive high-yielding,
agronomically desirable sorghum lines in which
the P-721 gene had survived. Some 197 homozygous
opaque F 6 lines survived and after a final
screening against lodging, stalk rot, and foliar
diseases in Puerto Rico, VanScoyoc (1979) tested
the best 158 lines, 11 elite normal cultivars from
international trials, and RS 671 for yield (Fig. 6).
Several of the elite normal lines (the P-954 series)
have yielded very well in Africa.
Yields of the 158 P-721 lines and the 11 elite
normal lines were divided into three classes: 22
with low yield, 111 with intermediate yield, and 36
with high yield. All check lines were in the
high-yield class. Among entries that yielded above
8.0 t/ha, the 12 opaque lines and the 7 vitreous
controls gave mean yields of 8.5 t/ha. Among
entries yielding above 7.6 t/ha, the mean for 24
opaque endosperm lines was only slightly less
than that for the 12 checks (8.1 vs 8.2 t/ha,
respectively). These data indicate that lines with
the P-721 opaque gene can yield as well as the
best normal sorghum cultivars if the gene occurs
in the proper genetic background. Earlier, Christensen
(1978), by studying a subset of the P-721
lines in F 5 breeding lines, also showed that the
P-721 opaque gene when placed in an appropriate
genetic background would not reduce grain yield
potential (Table 4). Because seed weight was
reduced about 15% by the P-721 opaque gene,
we speculate that selection for grain yield in P-721
lines must have resulted in an increase in the
number of seeds per panicle and/or the number
of panicles per unit area in order to have maintained
a good yield level (Axtell et a). 1979). It is
likely that variations in sorghum panicle morphology
allows compensation for reduced seed weight
by increasing seed numbers per panicle.
Acceptance of high-lysine sorghum cultivars
will be limited by problems associated with the
opaque kernel phenotype. Ejeta (1979) was successful
in identifying several lines with vitreous
endosperm and high lysine content. Subsequently,
these proved to be stable for vitreous endosperm
phenotype and high lysine concentration.
Also, seed treatments of P-721 opaque, highlysine
sorghum lines with DES resulted in
mutants with vitreous endosperm and high lysine
concentration (Porter 1977; Ejeta 1979). In general,
the lines with modified vitreous endosperm
from both sources had higher kernel weight and
lower percentages of protein and lysine (Table 5).
Also, the most vitreous types had the highest test
weight.
A replicated yield trial of 35 opaque lines and 11
normal lines at two locations in Indiana has
recently been completed. The results are presented
in Table 6. The mean grain yield of the top
three P-721 opaque lines is similar to that of the
top three normal checks in the trial. The dye
binding capacity (DBC) of the high yielding P-721
derived lines is intermediate between the checks
and that of the original P-721 opaque line.
Future studies with regard to the food-making
characteristics of the high-lysine lines will reveal
new possibilities and drawbacks. Thus we can
await that the milling quality of the more vitreous
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