ICRISAT Archival Report 2006 - The seedlings of success in the ...

complete block design with three replications. Same set of hybrids and their parents were screened for grain mold
and shoot fly in screening blocks.
Grain yield and other traits: There were significant differences amongst female nuclear genotypes for days to
50% flowering, plant height and grain yield but the differences were non-significant amongst R-lines. Similarly,
non-significant mean squares due to A × R-line interaction indicated that hybrids do not differ significantly for their
sca effects for grain yield. Cytoplasm per se appeared to have significant influence on the expression of hybrids for
plant height and grain yield, as evident from significant mean squares due to cytoplasm. It is important to note that
first-order interaction of cytoplasm with nuclear genetic background of A-lines (for all traits) or R-lines (for grain
yield) and second-order interaction with A-line and R-lines (for all traits) towards variation of iso-nuclear hybrids
was significant, suggesting significant but variable influence of cytoplasm for grain yield, depending on the genetic
background.
The comparison of A 1, A 2, A 3, A 4 (M) , A 4 (G) and A 4 (VZM) cytoplasms-based hybrids indicated that A 4 (M)
cytoplasm-based crosses were significantly earlier to flower compared to those based on A 3 and A 4 (VZM)
cytoplasms (though only by a day, which has no practical significance). A 2 cytoplasm-based hybrids were
significantly taller compared to A 3, A 4 (M), A 4 (G) and A 4 (VZM) cytoplasm-based hybrids by 6 to 9 cm, (which
again has no practical significance). A 1, A 2, A 3, A 4 (M) , A 4 (G) cytoplasm based hybrids were significantly superior
to A 4 (VZM) cytoplasm-based hybrids (by 1.0 t ha -1 ) and were comparable among themselves.
Thus, the comparable grain yield potential of A 2, A 3, A 4 (M) , A 4 (G) cytoplasms-based hybrids in similar maturity
and plant height backgrounds suggests the usefulness of A 2, A 3, A 4 (M) , A 4 (G) cytoplasms for diversifying the
cytoplasmic and nuclear genetic base of sorghum hybrid parents.
BVS Reddy
Grain mold resistance: There were significant differences amongst A-lines (nuclear genotype) and R-lines for
PGMR score, suggesting considerable differences among the parents for responses to grain mold. Significant mean
squares due to cytoplasm per se as for PGMR indicated that cytoplasms showed differential responses to grain mold.
The significant mean squares due to interaction of cytoplasms with A-lines and R-lines and A × R-lines interaction
suggested that the effect of cytoplasms was significantly influenced by the genetic backgrounds of both female and
male parents.
The comparison of A 1, A 2, A 3, A 4 (M) , A 4 (G) and A 4 (VZM) cytoplasms-based hybrids indicated that A 1, A 2, A 3, and
A 4 (VZM) cytoplasms-based hybrids were relatively less susceptible to grain mold than those based on A 4 (M) and A 4
(G) cytoplasms. However, when mean PGMR scores of different cytoplasms-based hybrids were examined, there
were seldom any differences in their responses to grain mold.
BVS Reddy and RP Thakur
Male-sterility-inducing cytoplasm vs normal fertile cytoplasm: Two sets of 36 (A × R) hybrids in iso-nuclear
alloplasmic backgrounds (36 in A 1 and 36 in A 2 ) were made by crossing iso-nuclear, alloplasmic A 1 and A 2 system
A-lines in 12 nuclear genetic backgrounds with three dual R-lines. The male-fertile counterparts of the 12 male-sterile
lines (B-lines) were emasculated and crossed with the same three dual R-lines and obtained 36 B × R crosses. The
two sets of 36 A × R and one set of 36 B × R crosses were evaluated at ICRISAT, Patancheru during the 2006 rainy
season in split-split-plot design using three replications by using R-lines in the main plots, A-lines as sub-plots and
cytoplasms as sub-sub-plots. The 12 A-lines and their B-lines were evaluated in a separate trial using randomized
complete block design with three replications. Sufficient care was taken for adequate supply of pollen grains to A-
lines for meaningful comparison of yield performance of A-lines vs. B-lines.
There were significant differences amongst A-/B-lines (nuclear genotype) and R-lines for plant height and grain yield
justifying the selection of the hybrid parents (A/B- and R-lines). Similarly, significant mean squares due to A-/B- ×
R-lines interaction indicate that hybrids differed significantly for their sca effects for grain yield. Cytoplasm per se
appeared to have significant influence on the expression of hybrids for plant height as evident from significant mean
squares due to cytoplasm. It is important to note that first-order interaction of cytoplasm with nuclear genetic
background of A-lines (for grain yield) or R-lines (for all the traits) and second-order interaction with A-line and R-
lines (for grain yield) towards variation of iso-nuclear hybrids were also significant, suggesting that the cytoplasm
was influenced by the genetic backgrounds of both male and female parents.
134