Studies on source sink relationship for realization of higher productivity in Bt cotton (Gossypium hirsutum L.)
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Date
2013
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PAU
Abstract
The present investigation entitled “Studies on source sink relationship for realization of higher productivity in Bt cotton (Gossypium hirsutum L)”comprising of three experiments (two field and one pot experiment) were carried out at the Research Farm, Department of Agronomy, Punjab Agricultural University, Ludhiana, during kharif seasons of 2011 and 2012. All the three experiments were laid out in split plot design with four replications. Three Bt cotton hybrids i.e. MRC 7017, MRC 7031 and RCH 314 were kept in main plots. The sub plot treatments in Experiment I consisted of 0 % (No square removal), 25 % removal (25 % squares removed for a period of month at pin head stage), 50 % removal (50 % squares removed for a period of month at pin head stage), P1 (fruits retained at first position), P2 (fruits retained at second position) and P1, 2 (fruits retained at first and second position). The Experiment II was a pot experiment comprising similar treatments as in Experiment I. The sub plot treatments in Experiment III consisted of control, detopping (removal of 5 to 7 cm apical portion of the main stem), MC application @ 300 ppm, TIBA @ 100 ppm and MH @ 250 ppm. Growth retardants and detopping treatments were applied at maximum vegetative growth stage i.e. 80 days after sowing (DAS).
The hybrid MRC 7017 attained maximum plant height and higher dry matter accumulation at all the growth stages than MRC 7031 and RCH 314 during both the years. The total number of main stem internodes plant -1 , height : node, SPAD value and monopodial branches plant -1 did not differ significantly among the three hybrids. Hybrid MRC 7017 produced significantly higher seed cotton yield by 15.0 to 19.1 per cent than hybrid RCH 314 whereas, it was statistically at par with hybrid MRC 7031
during both the years. Higher total seed cotton yield in MRC 7017 was attributed to the maximum number of sympodial branches plant -1, total number of flowers, bolls and picked bolls plant -1.
Fruiting form removal treatments had a significant influence on plant height and LAI at all the growth stages except at 60 DAS during both the years. A significant increase in plant height and LAI was bserved in 50 % square removal treatment at 90 DAS. While, at 120 DAS to maturity, P2 attained more plant height and LAI as compared to other fruiting form removal treatments. Accumulation of dry matter in vegetative parts was significantly higher in P2 while, dry matter accumulated in fruiting bodies was significantly higher in 0 and 25 % square removal treatments at 120 and 150 DAS during both the years. The treatment where 0 and 25 % squares were removed recorded higher number of flowers, total bolls and picked bolls plant -1 as compared to all other fruiting form removal treatments. The higher setting percentage in first fruit position (P1) resulted in significantly higher number of total bolls and picked bolls plant -1 than second fruit position i.e. P2 which eventually helped in producing significantly higher seed cotton yield than P2. Fruiting form removal delayed boll open initiation and 50 % boll opening by 4-11 days than 0 % square removal treatment. Boll weight in P1 improved by 5.6 to 11.8 per cent over control and all the fruiting form removal treatments helped in improving the boll weight as compared to control during both the years. Total seed cotton yield was maximum in 0 % square removal treatments as compared to all other fruiting form removal treatments.
Application of MC (300 ppm), TIBA (100 ppm) and MH (250 ppm) significant reduced plant height, LAI and total dry matter accumulation than control. Detopping treatment significantly reduced plant height than control but attained more plant height than all the PGRs. Application of PGRs resulted in significantly higher dry matter allocation towards fruiting bodies and less towards the vegetative plant organs which mproved setting percentage of bolls but did not regulate the CGR and RGR during different periods of crop growth. Different PGR treatments failed to influence the number of monopodial branches plant -1 while the number of sympodial branches plant -1 was highest with application of MC @ 300 ppm followed by TIBA (100 ppm) and MH (250 ppm) but significantly higher than control. The application of MC @ 300 ppm significantly influenced the total number of flowers produced plant -1 while, rest of the PGRs did not show any significant improvement in total number of flowers plant -1 over control.
Application of MC (300 ppm), TIBA (100 ppm) and MH (250 ppm) improved the total number of bolls, picked bolls plant -1 and boll weight. MC (300 ppm) increased the total seed cotton yield (22.79 and 31.62 q ha -1 in 2011 and 2012, respectively) as well as that obtained from first, second and third pick. TIBA (100 ppm) and MH (250 ppm) showed statistical similar results with MC (300 ppm) for the seed cotton yield obtained in all the pickings as well as in total seed cotton yield. Detopping failed to influence the seed cotton yield during both the years. Different quality parameters such as seed index, lint index and ginning out-turn were not significantly influenced by application of various PGR treatments.
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Keywords
Bt cotton hybrids, fruiting form removal, plant growth regulators, mepiquat chloride, 2,3,5-triiodo benzoic acid, maleic hydrazide, seed cotton yield