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Title: The Breeding Potential of Gossypium hirsutum L. For Water Deficit Conditions
Authors: Kamaran, Sohail
Keywords: Applied Sciences
Agriculture & related technologies
Plant breeding and genetics
Issue Date: 2018
Abstract: Drought is the most recurring environmental stress that reduces seed cotton yield, oil contents and fiber quality of cotton crop. Cotton provides raw material to textile sector, the most important sector of Pakistan. It provides livelihood to rural and urban people. Keeping in view the importance of cotton, present study was conducted in the glasshouse (Experiment 1) and research area (Experiment 2) of the Department of Plant Breeding and Genetics, University of Agriculture Faisalabad, Pakistan. Thirty upland BT cotton genotypes were collected from different research institutes (Department of Plant Breeding and Genetics, University of Agriculture Faisalabad, Central Cotton Research Institute (CCRI), Multan and Ayyub Agricultural Research Institute (AARI), Faisalabad. The genotypes/cultivars were screened for drought tolerance under glasshouse conditions on the basis of root length, shoot length, root dry and fresh weight, shoot fresh and dry weight, cell membrane stability, excised leaf water loss, stomatal conductance, transpiration rate, proline content and relative water content. Two tolerant (FH-114 and CIM-602) and two susceptible (TARZAN-1 and A-555) genotypes/cultivars were selected to develop F1, F2 and backcross populations. All populations (F1, F2, BC1 and BC2) developed from the crosses along with parents were grown under water deficit stress in field conditions. Drought stress was imposed by withholding water. Data regarding the traits, relative water content, excised leaf water loss, cell membrane stability, transpiration rate, stomatal conductance and proline content with different agronomic and fiber quality traits was recorded from F2 plants along with parental and back cross populations. The correlation analysis revealed that relative water content and cell membrane stability had correlation with yield. Positive correlation of relative water content with cell membrane stability revealed that the genes which help plant maintain relative water content may also be indirectly involved for cell membrane stability and could be associated with drought tolerance in cotton. Additive, dominance as well as gene interaction was found in the inheritance of almost all the traits under drought stress condition. Narrow sense heritability estimates showed that the traits were highly heritable so, considerable progress may be made in breeding for drought tolerance. All the genotypes were studied for genetic variation at molecular level using simple sequence repeat (SSR) markers. A total of 40 primers were tested for the estimation of genetic diversity among 30 parental genotypes, out of which 20 were found polymorphic. Total number of alleles amplified by these primers were 116 with an average of 5.8 allele per locus. Twenty primers were found to be polymorphic showing 13% genetic diversity. The genotypes FH-142 and TARZAN-1 were least similar among all the genotypes studied showing 78% similarity whereas, genotypes FH-113 and FH-114 showed high similarity (98%) among all. Genetic transformation was done via pollen tube mediated transformation method and GUS assay was performed on seed, embryo and leaf of transgenic plant progeny. Out of 200 plants assayed, only 7 T1 plant seedlings showed intense activity of GUS. Polymerase chain reaction also confirmed the presence of bar and dreb2 genes in the transformed plants. So, pollen tube mediated transformation could be effective for developing drought tolerant material. It is also suggested that exotic germplasm must be included in the present breeding material to broaden the genetic base so that varieties could be developed having better yield and tolerance to drought stress. On the basis of results deduced from present studies, it is concluded that agronomic, physiological, biochemical and molecular approaches could be used to develop better yielding genotypes with good quality fiber having tolerance against drought stress.
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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