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Development of earliness in cotton plant without sacrificing yield is a prime objective of cotton breeders. Early maturing
genotypes provide more efficient wheat-cotton-wheat rotation, also provide escape mechanism from biotic and abiotic
stresses, reduce the input resources and extend the period for harvesting and ginning operations. To examine the genetic
diversity of earliness in G. hirsutum L., 45 diverse genotypes collected from different research institutes of Punjab, were
screened for their earliness related traits and seed cotton yield (SCY) in field conditions. Index scores and principal
component analysis separately generated three distinct groups on the basis of their maturity viz; late maturing and high
yielding group 1, early maturing group 3, and group 2 had both types of genotypes. From these groups, six high yielding
early maturing genotypes (FH-682, FH-2015, MALMAL, MNH-147, PB-900, VH-300) were selected as lines, and
hybridized with five late maturing selected genotypes (B-557, BH-121, FH-941, MNH-93, MS-40) as male parents in line ×
tester fashion. General and specific combining ability effects of parents, on earliness related traits and SCY, were studied by
planting the parents and their crosses in the field under three nitrogen levels (60, 120 and 180 kg/ha). The experimental
design was a split plot arrangement. The L × T analysis of combining ability resulted significant variation among genotypes
(parents and crosses) for all studied traits. The gca and sca variances and their ratio exhibited pre-dominance of non-additive
gene action for almost all studied traits under all of three nitrogen levels, except for SCY (under 60 kg/ha). The GCA effects
revealed the line, MNH-147 as best combiner for majority of earliness related traits and FH-682 was observed best general
combiner for SCY and earliness index (EI) under all the three nitrogen levels. Best hybrid combinations identified were
MALMAL × MS-40 for node number for first fruiting branch (NNFFB), FH-682 × MS-40 for days to flowering (DTF) and
FH-682 × MNH-93 for EI. A few combinations, like FH-682 × MNH-93, FH-2015 × B-557, MNH-147 × MS-40, PB-900 ×
MNH-93 and VH-300 × FH-941, having harmonious combination of some earliness related traits along with yield traits,
have also been identified under the three nitrogen levels. Higher proportion of dominance variance in all the studied traits
suggested delayed selection or these crosses depicted remarkable potential to be exploited through heterosis breeding.
Sidra Ashiq Rana, Asif Ali, Muhammad Ahsan Iqbal, Iftikhar Ahmed Khan. (2021) GENETICS OF EARLINESS IN G. hirsutum L. UNDER DIFFERENT NITROGEN LEVELS, Pakistan Journal of Agricultural Sciences, Volume 58, Issue 3.
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