Browsing by Subject "maturity"
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Item Improvement of Cotton Fiber Maturity and Assessment of Intra-Plant Fiber Variability(2012-10-19) Kothari, NehaThe temporal system of fruiting on the cotton plant lends itself to bolls at different fruiting sites developing under different environmental conditions and with varied source-sink relationships. To investigate this, intra-plant fiber quality was assessed in four upland cultivars at College Station, Texas for three years and at Lubbock, Texas for two years. It was concluded that fiber quality steadily declines from the bottom sympodial branches towards the upper branches. 'FiberMax 832' had the best fiber quality among all cultivars but it also had the highest degree of variability within the plants. 'Half and Half' and 'Acala 1517-99' appear to have the least amount of intra-plant variability of fiber quality. Bolls from the bottom region of the plant have higher trash content compared to the upper region. To test the impact of fiber quality variability on boll sampling techniques employed, ten sampling protocols were compared against each other for three years in College Station, Texas, for two upland cultivars. Results suggest that randomized boll samples containing 50 bolls worked well to estimate inherent fiber quality for most fiber traits while estimation of trash and lint percent was not predictable based on boll samples. One of the problems associated with intra-plant fiber variability was the presence of immature fibers. In order to determine the potential for improvement of fiber maturity and standard fineness, five upland cotton (Gossypium hirsutum L.) genotypes were subjected to a diallel analysis at College Station, Texas, in 2011. Four cultivars that tend to produce fine and mature fibers and one cultivar that tends to produce coarse fibers were intermated in all combinations, without reciprocals. Estimates of general (GCA) and specific combining ability (SCA) for fiber maturity ratio and standard fineness based on Griffing's diallel Model I, Method 4 were calculated for AFIS and fiber micronaire, length and strength measurements for High Volume Instrument (HVI). Four parents had significant GCA effects and Acala 1517-99 was found to be the best parent for improving standard fineness followed by FiberMax 832 and 'Tamcot HQ-95'. Tamcot HQ-95 was the best parent to improve fiber maturity ratio while 'Deltapine 90' was the best parent to reduce fiber maturity ratio. The specific cross between Acala 1517-99 and Tamcot HQ-95 had the best performance. Diallel analysis indicated that fiber maturity ratio was influenced by non-additive gene effects more than additive gene effects while fiber standard fineness was highly influenced by additive gene effects. Developing cultivars with optimal fiber standard fineness and maturity should be prioritized to address problems associated with neps and short fiber content and improve spinning performance of US cotton.Item Maturity Elongation of Mid-Season Upland Cotton Varieties Through the Use of Pyraclostrobin and Azoxystrobin Fungicides(2014-04-29) Rocconi, John DavidCotton (Gossypium hirsutum L.) is subject to stress and yield reducing factors throughout the growing season. The loss of Delta and Pine Land 555 Bollgard? Roundup Ready? (DPL 555 BR) cotton in September 2009 removes a variety from the commercial market that proved to be a useful tool for farmers. This true full-season variety gave producers in regions of the U.S. Cotton Belt, where long growing season windows are established, the opportunity to take full advantage of extended growing days until harvest. The potential to delay the maturity of a mid-full season upland cotton variety, to that of the established full season variety, DPL 555 BR, may be possible through the determent of stress with fungicides. A two-year field study was conducted at the Texas AgriLife Research Farm in Burleson County in 2008 and 2009. The study evaluated the impact of pyraclostrobin, Headline?, and azoxystrobin, Quadris?, fungicides and their effect on yield and maturity after application to a mid-full season upland cotton variety, Stoneville 4554 Bollgard II? Roundup Ready Flex? (STV 4554 B2RF). These fungicides, along with commercially available tank-mix compounds, were applied to the study area at two defined growth stages: Early Bloom (EB), and Early Bloom +14 days (EB+14). Data analyzed over the years of both studies indicated statistical and numerical differences for fungicidal treatments. Statistical differences were noted in measurements throughout the years of both Study 1 and Study 2. Final plant mapping measurements and fiber properties for both studies failed to show improvements of increased nodes or plant height, as well as the measurements obtained from HVI analysis, due to the additions of either pyraclostrobin or azoxystrobin compounds. Combining these strobilurin fungicides with the labeled compounds of mepiquat chloride or mepiquat chloride did not yield results detrimental to plant characteristics measured in these studies. The treatment timing of EB+14 that contained the pyraclostrobin compound increased lint yield versus the untreated control by 213 kg ha^(-1).