| Cotton is the most important textile resource in the world. High yield is one of the maingoals in cotton breeding. The genetic theory of yield trait is significant to cotton yieldbreeding. Lint percentage is one of the three main factors of cotton fiber yield. And theformation of lint percentage is high related with fiber protrusion, fiber elongation andsecondary wall thickening. So study on QTL mapping for lint related traits and lint percentageformation mechanism is essential to cotton breeding.High lint percentage CSILs IL-08-7×TM-1F2were used to locate lint percentage relatedgenes. In fiber initiation development, fiber protrusion density, fiber elongation density,physiological and biochemical indexes were comparatively studied. And the relationshipbeween fiber protrusion density, fiber elongation density, fiber weight, average fiber length,fiber weight per unit length, fiber numbers and lint percentage were studied in the paper.1. Map QTL for lint percentage and fiber quality on the introgression segment IL-08-7Three QTLs for lint percentage and quality were mapped on the introgression segment ofIL-08-7(Chr. D1) including one QTL for length (q-LEN-D1), explaining7.27%for phenotypicvariance; one QTL for strength (q-STR-D1), explaining2.75%for phenotypic variance, oneinteraction QTL, explaining1.75%for phenotypic variance, respectively.2. Relationship between fiber protrusion density, elongation density and lint percentagein fiber initiation developmentFiber protrusion is highly related with gene type and germplasm, yet fiber elongation isclosely related with lint percentage. The ovule SEM indicate that six CSILs, TM-1andH7124’s fiber protrusion density and elongation density at1dpa and2dpa are the highest atthe funicular crest, higher at the chalazal cap and the middle part of ovule, and the least nearthe micropyle. Fiber elongation at2dpa are lower than fiber protrusion density at1dpa, whichindicate that the fiber cell are increasing expand as the growing of cotton ovule. In conclusion,early for fiber elongation have advantage to form high protrusion density, elongation densityand fiber number, which result in a high lint percentage, yet late for fiber elongation havedisadvantage to form protrusion density, elongation density and fiber number, resulting in alow lint percentage.3. The study of physiological and biochemical indexes in fiber initiation development From1day before anthesis to2dpa (days post anthesis) is a crucial period for the ovuleepidermal cell protrusion and from2dpa to15dpa is an important period for fiber rapidelongation. The content of soluble protein of high lint percentage IL-08-7is lower than TM-1,and low lint percentage IL-16-2-1is higher than TM-1, when the fiber start to protrude. It ispossible that low soluble protein have advantage to fiber protrusion and the increase of lintpercentage. From one day before anthesis to2dpa the soluble peroxidase of IL-08-7is lowerthan TM-1, and IL-16-2-1is higher than TM-1.It is possible that high soluble POD havedisadvantage to fiber protrusion and lead to the decrease of lint percentage. The content ofIAA oxidase of IL-08-7is lower than TM-1, and IL-16-2-1is higher than TM-1, when is theimportant period of ovule epidermal cell protrusion, primary cell wall synthesis and fiberelongation. It is possible that high level IAA oxidase have disadvantage to the formation oflint and lead to decrease lint percentage.4. The path analysis of CSILs varied in lint percentageThe Direct path cofficients of fiber protrusion density, elongation density, fiber weight,average fiber length, fiber weight in per unit legth and fiber number to lint percentage werestudied in this paper: fiber weight> fiber weight in per unit length>average fiber length> fiberprotrusion density>fiber elongation density, indicating that fiber weight, fiber weight in perunit length and average fiber length play important roles in lint percentage formation. |
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