HETEROSIS BREEDING FOR CROSSING PRESENT YIELD BARRIERS IN COTTON

Abstract                                                                         Back to Table of contents

India is the first country in the world to commercially exploit the phenomenon of heterosis in cotton.  At present 27% of the total area under cotton in India is grown under hybrids but their share of total cotton production is more than 40%.  In India, the cultivation of hybrids remained restricted to central and southern cotton zones since no hybrid was successful under north Indian conditions.  The long-duration hybrids were not suitable under the double cropping system (cotton-wheat rotation) followed in the Punjab and the northern zone.  The heterosis breeding work got impetus with the development of short duration, high yielding varieties like LH886, F846, LH900 and F1054 and the sanctioning of a hybrid project by the Indian Council of Agricultural Research in 1989.  Concerted efforts were made for the development of early maturing and high yielding intra hirsutum hybrids suitable for Punjab conditions.  From 1989 to 1993 a total of 535 hybrids have been developed by hand emasculation and hand pollination and evaluated in different trials in the state.  Intra-hirsutum hybrids identified were: LHH107, LHH121, LHH144, LHH212, LHH185, LHH315, LHH332, LHH468, LHH505, LHH565, LHH601 and LHH608.  These hybrids possess high yield potential and short duration and are suitable under a cotton-wheat rotation.  An intra-hirsutum hybrid ‘Fateh’ has been recommended by the Punjab Agricultural University in 1993 and hybrids LHH107, LHH121 and LHH 144 are at advanced stages of evaluation.  The hybrids identified for Punjab conditions combine earliness (170-175 days to maturity), big boll size (5.0 g) monopodial plant habit (1-5 monopods), superior fibre quality characters (2.5% span length more than 26 mm), tolerance to sucking pests and seed cotton yield 40% higher than varieties.

Conclusion

Heterosis breeding offers considerable opportunity for increasing productivity of cotton in the world. The observed heterosis of over 150% in test cross nurseries over check varieties and more than 50% commercial heterosis in replicated multi row multilocation trials conducted at Punjab Agricultural University have demonstrated the potential of hybrids over high yielding varieties.  Heterosis is maintained even under stress environments, especially rainfed farming.  Productivity of cotton in India has increased 112% since the release of the first cotton hybrid H4 in 1970. However success in hybrid cotton is not easy. The seed production technology has to be perfected to make it economically feasible by using cytoplasmic and genetic male sterility systems and by regional/international cooperation. The promotion of heterosis breeding in cotton to meet the future challenges for increasing fibre production and to provide clothing to the ever increasing human population should be given high priority.

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COTTON RESEARCH AND PRODUCTION IN BANGLADESH

Introduction                                                                 Back to Table of contents

In Bangladesh, Upland cotton is grown between latitudes 23˚ N and 26˚ N, at an altitude of just a few metres above sea level.  Production is almost entirely in the hands of smallholders, cultivating plots of 0.4 hectares of less.  Almost 90% of the crop is produced in the western region, with the remainder coming from the northern and central parts of the country.  Following its commercial reintroduction in 1977-78, the land under Upland cotton increased to a maximum of 17000 hectares in the 1982-93 season.  Since then the area has fluctuated widely, partly because of extensive flooding in the 1984-85 and 1987-88 seasons, and partly because of marketing difficulties.  Maximum production was achieved in the 1981-82 season, with an estimated 4145 tonnes of lint…

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DEVELOPMENT OF MEDIUM STAPLE HIGH STRENGTH COTTON SUITABLE FOR ROTOR SPINNING SYSTEMS

Abstract                                                                         Back to Table of contents

A major breakthrough in cotton spinning technology was achieved about three decades ago when the open-end (OE) spinning system was developed. Among the different versions developed such as Rotor, Friction and Air-jet, the first one has gained most popularity and is widely adopted all over the world. Compared with the conventional ring spinning, the rate of yarn production in OE system is about five times higher and is more economical. Further, the yarn evenness of OE yarn is superior to ring yarn. However, the tenacity of OE yarn is weaker by about 15-20% as compared with that of ring yarn for the same count. To overcome this deficiency, spinners are demanding cottons with high fibre strength which has become the most important fibre quality parameter for OE spinning.

Accordingly, breeders have initiated research programmes for evolving cotton varieties that have high fibre strength. Recently, in India,  a few lines of Pusa 2 (G. hirsutum) have been bred which possess fibre bundle tenacity as high as 53 – 56 g/tex at zero gauge and 33 – 36 g/tex at 1/8 in. gauge and with suitable combination of other fibre properties. In OE spinning tests, two lines of Pusa 2 performed excellently, recording CSP values as high as 2800 and 2460 at 20s and 30s counts (Ne).  Analysis of physical, morphological and geometric features of fibres and their cross-sections has revealed that homogeneity in all these characters is essential for a fibre to be strong. This paper discusses details of the developments and it is shown that the challenging demands of modern spinning technologies can be met effectively.

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NEW HORIZONS IN LINT PERCENTAGE IN PAKISTAN

Abstract                                                                         Back to Table of contents

Cotton is primarily grown for lint which is approximately 35% of the harvested seed cotton (seed and lint).  As a result of plant breeding efforts, this percentage has been increased up to 45% in various parts of the world.  Pakistan inherited varieties with values up to 32% and staple length 22 mm.  MNH 93 contributed the first break through by producing seed cotton with 37.5% lint and 28.5 mm staple length.  MNH 93 was released in 1980 and is still under cultivation.  S 12 with 40% lint gave another big jump and increased production to a record level.  MNH 147 (1992) has surpassed even S 12 with lint value of 42% and staple length 28.2 mm.

Extraordinary research efforts are being undertaken at cotton research institutions in Pakistan.  At Cotton Research Station, Multan, the efforts have resulted in achieving 51.8% lint.  The future targets include achieving lint level exceeding 60%.

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STUDIES OF QUANTITATIVE CHARACTERS IN UPLAND COTTON

Abstract                                                                         Back to Table of contents

Genetic analysis was performed through sequential model fittings to analyse the variation among generations derived from a cross of two diverse parents Bikaneri Narma and Model for seed cotton yield per plant, number of bolls per plant, boll weight, ginning outturn and lint index.  The analysis indicated that a trigenic epistatic model was most adequate for all the characters to explain inheritance.  Epistasis was found to be an integral part in the genetic control of all the characters studied. The higher magnitude of non-additive genetic component than additive component was observed in most of the characters, though additive component was found significant for seed cotton yield, boll weight and for ginning outturn. The implications of the present study in the improvement of populations derived from this cross are discussed.

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HYBRID COTTON RESULTS AND PROSPECTS

Abstract                                                                         Back to Table of contents

Hybrid 4 ushered in the era of hybrid cotton in India in the 1970s.  Hybrids both intra and interspecific now occupy about 28% of the cotton area and contribute about 42% of production of the country.  Inspired by the unique success of hybrid cotton in India, researchers in many cotton growing countries intensified their research on hybrid cotton.  A sizeable area is devoted to F1 and F2 hybrids in China.  In many other countries F1 or F2 hybrids are a distinct possibility in the near future.  The high cost of seed, which is a deterrent for the development or spread of hybrids can be overcome by exploiting male sterile systems coupled with bee pollination.  For hybrids to be successful they should be very high yielding, early maturing, moderately resistant to biotic and abiotic stresses with good fibre properties and above all, they have to be more profitable than varieties to attract farmers to grow them.

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