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Leon G. Higley - One of the best experts on this subject based on the ideXlab platform.
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Yield Responses of Alfalfa to Simulated Alfalfa Weevil Injury and Development of Economic Injury Levels
Agronomy Journal, 1993Co-Authors: Robert K. D. Peterson, Stephen D. Danielson, Leon G. HigleyAbstract:Although the Alfalfa weevil Hypera postica (Gyllenhal)] is an important Alfalfa (Medicago sativa L.) pest, relatively little is known about how defoliation at specific plant developmental stages affects yield. This study was conducted to characterize yield responses of Alfalfa to simulated Alfalfa weevil injury when injury was initiated at the early hud stage of the first growth cycle and to develop economic injury levels for the Alfalfa weevil. The study was conducted on a silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) in a 3.6-ha Alfalfa (cv. Haymaker) field near Walton, NE [...]
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Photosynthetic Responses of Alfalfa to Actual and Simulated Alfalfa Weevil (Coleoptera: Curculionidae) Injury
Environmental Entomology, 1992Co-Authors: Robert K. D. Peterson, Stephen D. Danielson, Leon G. HigleyAbstract:The Alfalfa weevil, Hypera postica (Gyllenhal), is the most important leafmass consumer of Alfalfa, Medicago sativa L. However, little is known about how insect defoliation injury affects photosynthetic responses of Alfalfa. Studies were conducted in 1990 and 1991 to characterize the gas exchange responses of Alfalfa to simulated and actual Alfalfa weevil larval injury. Gas exchange responses were observed for two levels of plant organization: (1) the remaining tissue of injured leaves and (2) the remaining leaves of defoliated plants. Transpiration and stomatal conductance rates for leaves with actual and simulated Alfalfa weevil injury were greater than for leaves without defoliation injury. However, photosynthetic rates of leaves with simulated and actual Alfalfa weevil injury were not significantly different from each other or from leaves without defoliation injury. Consequently, both simulated and actual Alfalfa weevil injury did not seem to affect the photosynthetic apparatus of the remaining leaf tissue. Therefore, the principal effect of Alfalfa weevil defoliation injury on photosynthetic responses of Alfalfa was to reduce the amount of photosynthesizing leaf tissue, but not photosynthetic rates. Moreover, simulated Alfalfa weevil injury techniques produced photosynthetic responses that were not significantly different from actual Alfalfa weevil injury. Defoliated plants responded to simulated Alfalfa weevil injury by altering the normal senescence pattern of the remaining leaves. In particular, leaves of defoliated plants maintained higher photosynthetic rates than corresponding leaves of control plants, which showed normal senescence patterns of decreasing photosynthetic rates. As defoliation injury increased in magnitude, leaf senescence of the remaining leaves proceeded at a progressively slower rate. Delayed leaf senescence seems to be a plant compensatory response to Alfalfa weevil defoliation injury.
Robert K. D. Peterson - One of the best experts on this subject based on the ideXlab platform.
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Yield Responses of Alfalfa to Simulated Alfalfa Weevil Injury and Development of Economic Injury Levels
Agronomy Journal, 1993Co-Authors: Robert K. D. Peterson, Stephen D. Danielson, Leon G. HigleyAbstract:Although the Alfalfa weevil Hypera postica (Gyllenhal)] is an important Alfalfa (Medicago sativa L.) pest, relatively little is known about how defoliation at specific plant developmental stages affects yield. This study was conducted to characterize yield responses of Alfalfa to simulated Alfalfa weevil injury when injury was initiated at the early hud stage of the first growth cycle and to develop economic injury levels for the Alfalfa weevil. The study was conducted on a silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) in a 3.6-ha Alfalfa (cv. Haymaker) field near Walton, NE [...]
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Photosynthetic Responses of Alfalfa to Actual and Simulated Alfalfa Weevil (Coleoptera: Curculionidae) Injury
Environmental Entomology, 1992Co-Authors: Robert K. D. Peterson, Stephen D. Danielson, Leon G. HigleyAbstract:The Alfalfa weevil, Hypera postica (Gyllenhal), is the most important leafmass consumer of Alfalfa, Medicago sativa L. However, little is known about how insect defoliation injury affects photosynthetic responses of Alfalfa. Studies were conducted in 1990 and 1991 to characterize the gas exchange responses of Alfalfa to simulated and actual Alfalfa weevil larval injury. Gas exchange responses were observed for two levels of plant organization: (1) the remaining tissue of injured leaves and (2) the remaining leaves of defoliated plants. Transpiration and stomatal conductance rates for leaves with actual and simulated Alfalfa weevil injury were greater than for leaves without defoliation injury. However, photosynthetic rates of leaves with simulated and actual Alfalfa weevil injury were not significantly different from each other or from leaves without defoliation injury. Consequently, both simulated and actual Alfalfa weevil injury did not seem to affect the photosynthetic apparatus of the remaining leaf tissue. Therefore, the principal effect of Alfalfa weevil defoliation injury on photosynthetic responses of Alfalfa was to reduce the amount of photosynthesizing leaf tissue, but not photosynthetic rates. Moreover, simulated Alfalfa weevil injury techniques produced photosynthetic responses that were not significantly different from actual Alfalfa weevil injury. Defoliated plants responded to simulated Alfalfa weevil injury by altering the normal senescence pattern of the remaining leaves. In particular, leaves of defoliated plants maintained higher photosynthetic rates than corresponding leaves of control plants, which showed normal senescence patterns of decreasing photosynthetic rates. As defoliation injury increased in magnitude, leaf senescence of the remaining leaves proceeded at a progressively slower rate. Delayed leaf senescence seems to be a plant compensatory response to Alfalfa weevil defoliation injury.
S. S. Quisenberry - One of the best experts on this subject based on the ideXlab platform.
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Identification of Alfalfa resistance to the threecornered Alfalfa hopper (Homoptera : Membracidae)
Journal of Economic Entomology, 1992Co-Authors: D. J. Moellenbeck, S. S. QuisenberryAbstract:Six Alfalfa, Medicago sativa L., cultivars were screened in the greenhouse for antixenosis and antibiosis to the threecornered Alfalfa hopper, Spissistilus festinus (Say). The cultivars ‘Zia’ and ‘Cimarron VR’ showed antixenotic properties by harboring lower adult populations and exhibiting less girdle damage. ‘Cimarron’ was the most preferred cultivar based upon increased girdle damage and larger adult populations. In the antibiosis test, significant variation among the cultivars was found for adult male weights but not female weights, indicating sex-based differences in threecornered Alfalfa hopper susceptiblity to antibiotic factors. ‘Dona Ana’ exhibited antibiosis by decreasing male adult threecornered Alfalfa hopper weights; however, nymphal duration and female weights were not affected. Nymphal duration was significantly shorter on ‘Zia’ compared with ‘Florida 77’. Results show that variation in Alfalfa susceptibility to the threecornered Alfalfa hopper does exist, and further development of resistance may increase the importance of host-plant resistance in the management of this Alfalfa pest.
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Population Dynamics and Seasonal Biology of the Alfalfa Weevil (Coleoptera: Curculionidae) on Alfalfa in Louisiana
Environmental Entomology, 1990Co-Authors: Fred Whitford, S. S. QuisenberryAbstract:The biology of the Alfalfa weevil, Hypera postica (Gyllenhal), was studied in Louisiana during 1986 to 1988 on Alfalfa, Medicago sativa (L.). Post-estivation migration of adults in the fall occurs during late November and early December. Fall oviposition during December and January resulted in 58 to 81% of Alfalfa stems with egg clusters. Egg viability of eggs laid in the fall was estimated at 75%. Alfalfa weevil egg clusters contained an average of 10.9 (1986–1987) to 13.3 (1987–1988) eggs per cluster. The position of egg clusters in the Alfalfa canopy, relative to the base of the stem, indicated that 95 and 50% of all clusters were below 40 and 18 cm, respectively. An ovipositional preference was found with eggs generally laid between the upper 30% and lower 80% regions of the Alfalfa stem. Alfalfa weevil larvae were first detected in February. Egg eclosion in 1987 was highly synchronized as indicated by larval counts increasing from 4 to 90 per sweep between 3 and 10 February. In 1988, larval emergence gradually increased from 4 February (≦10/sweep) to 3 March (60/sweep). Head capsule widths were 0.15, 0.28, 0.42, and 0.55 mm for first, second, third, and fourth instars, respectively. Corresponding body lengths were 1.4, 2.8, 4.6, and 6.6 mm for first, second, third, and fourth instars, respectively. The marked decline of Alfalfa weevils in April is presumably indicative of adult migration from Alfalfa to summer estivation sites. Degree-day accumulations are used to describe and predict spring hatch of the Alfalfa weevil in Louisiana.
Shweta Deshpande - One of the best experts on this subject based on the ideXlab platform.
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Alfalfa benefits from medicago truncatula the rct1 gene from m truncatula confers broad spectrum resistance to anthracnose in Alfalfa
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Shengming Yang, Chenwu Xu, Shweta DeshpandeAbstract:Alfalfa is economically the most important forage legume worldwide. A recurrent challenge to Alfalfa production is the significant yield loss caused by disease. Although knowledge of molecular mechanisms underlying host resistance should facilitate the genetic improvement of Alfalfa, the acquisition of such knowledge is hampered by Alfalfa's tetrasomic inheritance and outcrossing nature. However, Alfalfa is congeneric with the reference legume Medicago truncatula, providing an opportunity to use M. truncatula as a surrogate to clone the counterparts of many agronomically important genes in Alfalfa. In particular, the high degree of sequence identity and remarkably conserved genome structure and function between the two species enables M. truncatula genes to be used directly in Alfalfa improvement. Here we report the map-based cloning of RCT1, a host resistance (R) gene in M. truncatula that confers resistance to multiple races of Colletotrichum trifolii, a hemibiotrophic fungal pathogen that causes anthracnose disease of Alfalfa. RCT1 is a member of the Toll-interleukin-1 receptor/nucleotide-binding site/leucine-rich repeat (TIR-NBS-LRR) class of plant R genes and confers broad-spectrum anthracnose resistance when transferred into susceptible Alfalfa plants. Thus, RCT1 provides a novel resource to develop anthracnose-resistant Alfalfa cultivars and contributes to our understanding of host resistance against the fungal genus Colletotrichum. This work demonstrates the potential of using M. truncatula genes for genetic improvement of Alfalfa.
Stephen D. Danielson - One of the best experts on this subject based on the ideXlab platform.
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Yield Responses of Alfalfa to Simulated Alfalfa Weevil Injury and Development of Economic Injury Levels
Agronomy Journal, 1993Co-Authors: Robert K. D. Peterson, Stephen D. Danielson, Leon G. HigleyAbstract:Although the Alfalfa weevil Hypera postica (Gyllenhal)] is an important Alfalfa (Medicago sativa L.) pest, relatively little is known about how defoliation at specific plant developmental stages affects yield. This study was conducted to characterize yield responses of Alfalfa to simulated Alfalfa weevil injury when injury was initiated at the early hud stage of the first growth cycle and to develop economic injury levels for the Alfalfa weevil. The study was conducted on a silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) in a 3.6-ha Alfalfa (cv. Haymaker) field near Walton, NE [...]
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Photosynthetic Responses of Alfalfa to Actual and Simulated Alfalfa Weevil (Coleoptera: Curculionidae) Injury
Environmental Entomology, 1992Co-Authors: Robert K. D. Peterson, Stephen D. Danielson, Leon G. HigleyAbstract:The Alfalfa weevil, Hypera postica (Gyllenhal), is the most important leafmass consumer of Alfalfa, Medicago sativa L. However, little is known about how insect defoliation injury affects photosynthetic responses of Alfalfa. Studies were conducted in 1990 and 1991 to characterize the gas exchange responses of Alfalfa to simulated and actual Alfalfa weevil larval injury. Gas exchange responses were observed for two levels of plant organization: (1) the remaining tissue of injured leaves and (2) the remaining leaves of defoliated plants. Transpiration and stomatal conductance rates for leaves with actual and simulated Alfalfa weevil injury were greater than for leaves without defoliation injury. However, photosynthetic rates of leaves with simulated and actual Alfalfa weevil injury were not significantly different from each other or from leaves without defoliation injury. Consequently, both simulated and actual Alfalfa weevil injury did not seem to affect the photosynthetic apparatus of the remaining leaf tissue. Therefore, the principal effect of Alfalfa weevil defoliation injury on photosynthetic responses of Alfalfa was to reduce the amount of photosynthesizing leaf tissue, but not photosynthetic rates. Moreover, simulated Alfalfa weevil injury techniques produced photosynthetic responses that were not significantly different from actual Alfalfa weevil injury. Defoliated plants responded to simulated Alfalfa weevil injury by altering the normal senescence pattern of the remaining leaves. In particular, leaves of defoliated plants maintained higher photosynthetic rates than corresponding leaves of control plants, which showed normal senescence patterns of decreasing photosynthetic rates. As defoliation injury increased in magnitude, leaf senescence of the remaining leaves proceeded at a progressively slower rate. Delayed leaf senescence seems to be a plant compensatory response to Alfalfa weevil defoliation injury.
