GENETICS OF SEED YIELD AND ITS COMPONENT TRAITS IN CASTOR (Ricinus communis L.), 2802
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Date
2019-06
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JAU, JUNAGADH
Abstract
The present investigation was undertaken with a view to investigate genetic
basis of seed yield and its component traits, to study the extent of heterosis and
inbreeding depression and underlying genetic causes for different traits in castor. The
experimental materials consisted of twelve generations, namely P1, P2, F1, F2, B1, B2,
B11, B12, B21, B22, B1s and B2s of four crosses of castor viz., JP 104 x JI 433 (cross 1),
SKP 84 x JI 433 (cross 2), SKP 84 x JI 437 (cross 3) and SKP 84 x JI 441 (cross 4).
Experiment was laid-out in Compact Family Block Design with three replications
during Kharif 2017 at Sagdividi Farm, Department of Seed Science and Technology,
College of Agriculture, Junagadh Agricultural University, Junagadh. The observations
were recorded on twelve characters viz., days to flowering of primary raceme, days to
maturity of primary raceme, plant height up to primary raceme (cm), number of nodes
up to primary raceme, length of primary raceme (cm), effective length primary
raceme (cm), number of effective branches per plant, number of capsules on primary
raceme, shelling out turn (%), 100 seed weight (g), seed yield per plant (g) and oil
content (%) on five randomly selected plants in each replication for P1, P2 and F1;
fifteen plants for B1 and B2; and twenty five plants for each of F2, B11, B12, B21, B22,
B1s and B2s.
The analysis of variance between families (crosses) revealed that the mean
squares due to crosses were significant for all the characters studied except oil
content. The analysis of variance among progenies within each family indicated
significant differences among twelve generation means for all the characters studied
in all the four crosses.
Mean performance of F1 hybrids exceeded the value of their better parent in
desired direction for length of primary raceme and effective length of primary raceme
in JP 104 x JI 433 and SKP 84 x JI 441; for number of effective branches per plant
and 100 seed weight in SKP 84 x JI 441; for oil content in JP 104 x JI 433 and SKP
84 x JI 433; for number of nodes up to primary raceme in SKP 84 x JI 433, SKP 84 x
JI 437 and SKP 84 x JI 441; and for number of capsules on primary raceme and
shelling out turn in SKP 84 x JI 437. None of the F1 exceeded the seed yield per plant
over their better parent in positive direction. The per se performance of F1 was lower
than its better parent for plant height up to primary raceme in crosses SKP 84 x JI 437
and SKP 84 x JI 441 and for number of nodes up to primary raceme in cross JP 104 x JI 433, while for days to flowering of primary raceme and days to maturity of primary
raceme, none of the F1 per se was lower than its better parent. Mean performance of
backcross progenies was not consistent in different crosses for different traits,
however, several back crosses exceeded the mean performance over their better parent
in desirable direction for seed yield per plant and its component traits. With respect to
seed yield per plant, back cross progenies B11, B21 and B1s in cross JP 104 x JI 433;
B1, B12, B21, B22 and B1s in cross SKP 84 x JI 433; all the backcross progenies in
crosses SKP 84 x JI 437; and all the backcross progenies except B1 in cross SKP 84 x
JI 441 exceeded the mean performance over their better parents.
Significance of simple scaling tests and Cavaliโs joint scaling test indicated the
presence of gene interactions for all the traits in all four crosses. Based on six parameter model of Hill (1966), a valid conclusion can be drawn by the ๐
2
(2) value at
six degrees of freedom about the presence of higher order epistasis. The significant
๐
2
(2) pointed out presence of trigenic or higher order epistasis in all the crosses for all
the characters.
The trigenic ten-parameter model was found to be adequate in cross JP 104 x
JI 433 for effective length primary raceme; in crosses JP 104 x JI 433 and SKP 84 x JI
437 for number of capsules on primary raceme; and in cross SKP 84 x JI 441 for
number of effective branches per plant. On the other hand, ๐
2
(3) with two degrees of
freedom was found significant for remaining traits in all the four crosses showing the
presence of higher order epistasis and/or linkage. All the ten-parameters were
significant for shelling out turn percentage in two crosses SKP 84 x JI 437 and SKP
84 x JI 441 and for days to maturity of primary raceme in one cross SKP 84 x JI 433.
The heterosis over better parent was significant and positive in all four crosses
for days to flowering of primary raceme and days to maturity of primary raceme,
indicating delay in flowering and maturity in hybrid combinations. The heterosis over
better parent was significant and negative for dwarf stature in cross SKP 84 x JI 437.
The heterosis over better parent was significant and positive for longer length of
primary raceme in crosses JP 104 x JI 433 and SKP 84 x JI 441, for effective length
of primary raceme in cross JP 104 x JI 433, for shelling out turn in cross SKP 84 x JI
437, for test weight in SKP 84 x JI 441, and for oil content in JP 104 x JI 433 and
SKP 84 x JI 433. The heterobeltiosis was significant and negative in crosses JP 104 x
JI 433, SKP 84 x JI 433 and SKP 84 x JI 441 for seed yield per plant. Moderate
inbreeding depression was observed in the present study as a whole. The observed and
the expected estimates for heterosis over mid parent, over better parent and inbreeding
depression were in close agreement with one another for days to flowering of primary
raceme, days to maturity of primary raceme, plant height up to primary raceme,
number of nodes up to primary raceme, 100 seed weight and oil content in all four
crosses.
Overall from the present study, it could be concluded that seed yield per plant
and its component traits recorded in four castor crosses were governed by additive,
dominance and digenic and/or trigenic epistasis gene effects. Reciprocal recurrent
selection could be followed which would facilitate exploitation of both additive and
non-additive gene effects simultaneously for genetic improvement in castor.
Importance of duplicate type of gene action was observed for all of the characters
studied in all four crosses showing digenic/trigenic interaction. Under a situation of
this type, breeding procedures involving either multiple crosses or biparental crosses
may be restored to get transgressive segregants.