Khalequzzaman creator Datta, Avishek Chairperson Himanshu, Sushil Kumar Co-Chairperson Tsusaka, Takuji W. Examination Committee Zulfiqar, Farhad Examination Committee National Agricultural Technology Program - Phase II (NATP-II), Bangladesh Agricultural Research Council (BARC), Bangladesh Scholarship Donor text series theses th Pathum Thani, Thailand Asian Institute of Technology 2023 continuing eng

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178 leaves : ill.+ online resource Cotton (Gossypium hirsutum L.) is one of the most important cash crops for providing fiber as a raw material for textile industries. It is grown mainly in tropical and subtropical regions around the world. Expanding cotton cultivation to newer regions and increasing crop productivity are now prerequisites to cope with increasing industrial demand and uplift the economic conditions of the cotton farmers. However, it is challenging due to multiple constraints in crop management, deteriorating soil health, and environmental stresses, especially scarcity of irrigation water, changes in rainfall patterns, drought and heat spells, and salinization. Drought is a major abiotic stress that influences crop productivity by adversely affecting morphological, physiological, ecological, and biochemical characteristics of plants. The impacts of drought in agriculture are aggravating due to increasing temperatures, erratic rainfall, and depleting freshwater resources. Although cotton could adapt to drought/water deficit stress conditions because of its comparatively lower water requirements than other water-intensive crops (e.g., rice, maize, and vegetables), the peak bloom phenological stage remains highly sensitive to drought regarding lint and seed cotton yield. Thus, there is an urgent need to explore alternative management strategies to reduce cotton irrigation demand and sustain irrigated cotton production. Application of innovative agronomic management practices (nutrient management) coupled with plant growth regulator and an adoption of efficient water management strategy need to be integrated with existing cultivation practices to enhance crop tolerance against drought stress and maximize crop yield and water productivity for ensuring sustainable cotton production. Therefore, an interactive effect among nutrient management practice, plant growth regulator application, and irrigation water regime was evaluated through several laboratory and polyhouse experiments for cotton.In the first polyhouse experiment, the effect of six seed priming materials (priming with salicylic acid [SA] at100 mg L{u2013}1 , silicon [Si] at 1 mM, potassium nitrate [ KNO3] at 5 g L{u2013}1 , proline [PRO] at100 mg L{u2013}1 , glycine betaine [GB] at 100 mg L{u2013}1 , and hydropriming, and non-primed control) was assessed on cotton under three soil moisture levels (50, 75, and 100% field capacity [FC]) to compare the effectiveness of these priming materials in mitigating the detrimental effects of water-deficit stress. The cotton variety Tak Fa 7 (big boll size, high yield) was used as the test material. The results revealed a significant decrease in all evaluated parameters with reducing soil moisture levels (44{u2013}58% reduction in boll number per plant, 25{u2013}50% reduction in seed cotton yield, 18{u2013}41% reduction in lint index, 6{u2013}21% reduction in leaf relative water content, and 18{u2013}53% reduction in net photosynthetic rate at 50% FC in comparison to 100% FC) across seed priming treatments. However, there was up to a 9-fold increase in free proline concentration at 50% FC in comparison to 100% FC across seed priming treatments. Plants raised from KNO3- and GB-primed seeds outperformed all other treatments and caused a significant increase in germination-related traits and other evaluated parameters. There were 54, 36, and 125% higher shoot dry matter, seed cotton yield, and net photosynthetic rate, respectively, of KNO3- primed plants over the control plants (non-primed) at 50% FC, and 31, 11, and 79% higher single boll weight, leaf greenness, and membrane stability index, respectively, of GB-primed plants over the control (non-primed) at 50% FC. Priming cotton seeds with KNO3 at 5 g L{u2013}1 or GB at 100 mg L{u2013}1 can be recommended as a promising technique for growing cotton in water scarce environments.In the second laboratory and polyhouse experiments, the effect of seed priming with KNO3 on cotton productivity and fiber quality was evaluated under drought stress. A germination trial was established under laboratory conditions with five seed priming treatments (non-primed control, hydropriming, and priming with 2.5, 5.0, and 7.5 g L{u2013} 1 KNO3). A polyhouse experiment consisting of the same seed priming treatments was conducted under three soil moisture regimes (100%, 75%, and 50% FC). The effects were quantified based on data on germination traits, growth and reproductive parameters, yield components, seed cotton yield, water productivity, fiber quality, and physio-biochemical parameters. The results revealed a significant reduction in all evaluated parameters at 50% FC compared with 100% FC (39{u2013}54%, 32{u2013}44%, 5{u2013}15%, 6{u2013}7%, 6{u2013}12%, and 7{u2013}12% reduction in boll number per plant, seed cotton yield, ginning outturn, fiber length, fiber strength, and leaf relative water content, respectively, across seed priming treatments). Seed priming with KNO3 at 5 g L{u2013}1 was effective in alleviating the detrimental effects of drought stress and caused 60{u2013}109%, 61{u2013}73%, 14{u2013}27%, 13{u2013}16%, 16{u2013}23%, and 13{u2013}14% increase in boll number per plant, seed cotton yield, ginning outturn, fiber length, fiber strength, and leaf relative water content, respectively, across soil moisture regimes compared with the non-primed control. This treatment resulted in higher net photosynthetic rate, stomatal conductance, and transpiration rate at 50% FC compared with the non-primed control at the same soil moisture regime. Seed priming with 5 g L{u2013}1 KNO3 is recommended for synchronized germination and better productivity and fiber quality of cotton under limited water availability. This method could be used as potential technology in advancing sustainable agriculture in water-scarce environments.The third polyhouse experiment consisting of six Si and salicylic acid (SA) treatments (control, 60 kg ha{u2013}1 Si applied as a soil drench, 1 mM Si applied as a seed priming material, 1 mM SA applied as a foliar spray, 60 kg ha{u2013}1 Si applied as a soil drench + 1 mM SA applied as a foliar spray, seed priming with 1 mM Si + foliar spray of 1 mM SA) and three soil moisture regimes (100%, 75%, and 50% FC) was conducted to evaluate the individual and combined effects of Si and SA on growth, yield, and physiological responses of cotton plants under drought stress. Decreasing soil moisture level from 100% to 50% FC reduced growth (plant height by 18{u2013}26%, shoot dry matter by 46{u2013}53%, and root dry matter by 27{u2013}43%), seed cotton yield (45{u2013}55%), irrigation water productivity (41{u2013}54%), and physiological response (leaf relative water content by 11{u2013}17%, membrane stability index by 44{u2013}55%, and up to 102% increase in electrolyte leakage) of cotton plants across Si and SA doses. Among Si and SA doses, a combined application of seed priming with 1 mM Si + foliar spray of 1 mM SA outperformed all other doses and caused an increase of 14{u2013}20% in plant height, 78{u2013} 99% in root dry matter, 24{u2013}76% in seed cotton yield, 22{u2013}60% in irrigation water productivity, 9{u2013}14% in ginning outturn, and 40{u2013}94% in membrane stability index across soil moisture regimes. A combined application of Si at 1 mM as a seed priming material and SA at 1 mM as a foliar spray is recommended for cotton cultivation in drought-prone areas. A Dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Agricultural Systems and Engineering Thesis (Ph.D.) - Asian Institute of Technology, 2023 Plants Effect of stress on Plants Drought tolerance Water in agriculture Cotton Asian Institute of Technology. Dissertation ; http://203.159.5.9/ait-thesis/detail.php?q=B21499 http://203.159.5.9/ait-thesis/detail.php?q=B21499 241004 20260817162129.0