GENETIC ANALYSIS OF STALK SUGAR YIELD AND ITS COMPONENT TRAITS IN SWEET SORGHUM [Sorghum bicolor (L.) Moench]
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Date
2011-01
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY
Abstract
Generation mean analysis was carried out to estimate the nature and
magnitude of gene effects for sugar yield and its component traits in sweet
sorghum [Sorghum bicolor (L.) Moench]. Six basic generations, namely P1, P2, F1,
F2, BC1P1, BC1P2 of four crosses involving seven diverse parents were evaluated
in rainy seasons 2009 and 2010. The means of all six generations in all the crosses
indicated higher F1 means than mid parent and better parent values in majority of
the characters. F1 means were higher than mid-parental values and/or comparable
to better parent mean values in respect of all the traits in both seasons except days
to 50 per cent flowering which indicated presence of both partial and over
dominance. The F2 means were lesser than the F1 means. The means of backcross
populations tended towards their respective parents.
Scaling and joint scaling tests revealed inadequacy of simple additivedominance
model to explain the observed variation of all the traits in both
seasons, providing an evidence for the presence of epistasis in all the crosses. The
six generation mean analysis in all the four crosses indicated significance of both
additive and dominance gene effects. While, all the traits showed significance of
one or more interaction types (additive × additive [i] or additive × dominance [j]
or dominance × dominance [l]). Based on the signs of [h] and [l] components,
duplicate type (opposite sign) of gene interaction has been reported in the
inheritance of traits studied in all the four crosses with a few exceptions.
High degree of heterosis coupled with high magnitude of inbreeding
depression was reported for sugar yield and its important component characters
indicating the operation of the non-additive gene action. Consistency in the
performance of the hybrids over the crosses and seasons was observed or all the
traits. Minimum number of effective factors influencing a trait in F2 population
ranged between one and ten.
Genetic variability studies in F2 population of four crosses revealed wide
range of variability for majority of the traits under study. The skewness and
kurtosis indicated the presence of both complementary and duplicate type of
interaction in the inheritance of characters. However, majority exhibited
platykurtic and positively skewed distribution suggesting the involvement of
relatively large number of segregating genes having decreasing effects and
dominance based complementary type of interaction. Higher per cent of GCV and
PCV were observed for all the traits. The estimates of heritability and genetic
advance as per cent of mean was observed to be high for all the traits
Correlation coefficient studies revealed significant positive correlation of
all component characters with sugar yield. Path analysis revealed high positive
direct effect of juice weight which was consistent over the seasons and crosses.
The selection indices formulated in F2 generation of one of the crosses indicated,
the three character combination including plant height, juice weight and Brix%
manifesting maximum relative efficiency coupled with genetic advance.
Description
Keywords
crossing over, yields, sugar, sorghum, genetics, genes, planting, additives, seasons, biological phenomena, SWEET SORGHUM, Sorghum bicolor (L.) Moench