[Show abstract][Hide abstract] ABSTRACT: Soybean aphids have become a serious pest of soybean, Glycine max L. (Merrill), since they were first detected in North America in 2000. Three soybean aphid biotypes have been documented in the United States in the last 10 yr, but few studies have been done on their feeding behavior in the United States The Electrical Penetration Graph is a convenient and successful tool to study the feeding behavior of piercing and sucking insects. This is the first attempt to study the feeding behavior differences between biotype 1 and biotype 2 on soybean genotypes using the Electrical Penetration Graph technique, and includes both resistant and susceptible soybean genotypes from Kansas and Michigan. The experiments were run for 9 h each for each genotype with a total of eight channels at a time. Results indicated that aphids feeding on susceptible genotypes had a significantly greater duration of sieve element phase than when feeding on resistant genotypes. Furthermore, the time taken to reach the first sieve element phase in resistant genotypes was significantly greater than in susceptible genotypes. Most of the aphids reached sieve element phase (> 90%) in susceptible genotypes, but only a few (< 30%) reached sieve element phase in resistant genotypes during the 9-h recording period; however, we found no differences in any other probing phases between resistant and susceptible genotypes except the number of potential drops in biotype 2. Thus, the resistance was largely associated with phloem tissues. Therefore, some biochemical, physical, or morphological factors could affect stylet penetration of aphids.
[Show abstract][Hide abstract] ABSTRACT: G reenbug [(Schizaphis graminum (Rondani) (Hemiptera: Aphididae)] is the most important insect pest of sor-ghum [Sorghum bicolor (L.) Moench.] in the southern Great Plains of the United States. This pest frequently causes severe crop damage and economic losses in sorghum pro-duction fields (Wilde and Tuinstra, 2000). Biotype I is the most widespread and dominant greenbug pest in sorghum and wheat [Triticum aestivum L.] fields, and also on many noncultivated grass species (Wu et al., 2007). Although genetic sources of resistance have been developed to mini-mize greenbug damage, new greenbug biotypes that over-come these sources of resistance appear every few years. It has been postulated that the known greenbug biotypes are preadapted opportunists that take advantage of geneti-cally uniform hosts and are clonally prolific on transient sorghum or wheat crops (Porter et al., 1997). This hypoth-esis suggests that early biotypes, like biotype E, were not replaced by later biotypes; rather, they remain widespread and will damage sorghum production if sorghum hybrids do not have the relevant resistance genes (Wu et al., 2007). We therefore undertook the development of lines with feeding tolerance to greenbug biotypes E, I, and K. Twelve sorghum germplasm lines KS were developed through population improvement for greenbug feeding tolerance and released by the Kansas Agricultural Experiment Station in October 2007.
[Show abstract][Hide abstract] ABSTRACT: The soybean aphid, Aphis glycine Matsumura (Hemiptera: Aphididae), is a major pest of soybean. In the current study, we used the Electrical Penetration Graph technique to study feeding behavior of soybean aphids on antibiotic-resistant soybean lines KS1621, KS1613, and KS1642, and a susceptible soybean line, KS4202. We observed that soybean aphids spent significantly shorter periods of time in the sieve element phase but slightly more times in nonprobing phases in all three resistant lines than in the susceptible control. Our study suggests that resistance factors exist in the phloem of the resistant soybean lines, and that these lines may contain antixenosis in addition to antibiosis.
[Show abstract][Hide abstract] ABSTRACT: Soybean, Glycine max (L.) Merr is one of the most important cultivated crops in the world .The soybean aphid, Aphis glycines Matsumura, is a major pest of soybean and was first detected in Wisconsin in 2000. It has spread into most, if not all, soybean producing areas of the United States and Canada since its first report. Host plant resistance to insects is an important alternative to other controls and is more sustainable than any other control methods against this insect. Recent studies identified two soybean aphid biotypes during 2005 in just five years after its invasion. This study includes the entries from Kansas, Michigan and Nebraska soybean germplasms. Also it is the first attempt to study the different Kansas soybean entries response to Ohio biotype. The plants were screened by infested at V1 stage with 6 aphids per plant and populations counted after 7 days. The results showed that the earlier resistant entries to Illinois biotype (K1639, K1642, K1613 K1621, Dowling and Jackson) were susceptible to the new Ohio biotype with large populations developing on these entries. But two of the Michigan entries (EO 6902 and EO 7906-2) showed resistance to both Ohio and Illinois biotypes. Further characterization of resistance made clear that they showed antibiosis type of resistance with the two above biotypes. Thus, it is concluded that we found two entries resistant to both Ohio and Illinois biotypes and the Ohio biotype overcame the several different sources of resistance in previous found resistant entries.
Entomological Society of America Annual Meeting 2009; 12/2009
[Show abstract][Hide abstract] ABSTRACT: The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is a worldwide pest of soybean, Glycine max (L.) Merr. Studies to find control methods were initiated in 2000 when it was first detected in North America. A. glycines can reduce yields by as much as 50%, and it is the vector of several viral diseases. A. glycines removes phloem sap, which can result in a reduction of chlorophyll content. Quantification of chlorophyll loss caused by A. glycines feeding on soybean is of vital importance. The SPAD-502 chlorophyll meter is a device that has been used to measure chlorophyll loss caused by nonchewing insects. Chlorophyll loss was studied in no-choice tests on the infested and uninfested leaves of a susceptible check (KS4202). The minimum combined number of days and aphids needed to detect significant chlorophyll loss was 30 aphids confined for 10 d. In a similar experiment, seven resistant entries and two susceptible checks were evaluated. There was no significant chlorophyll reduction between infested and uninfested leaves of five of the resistant entries (K1621, K1639, Pioneer 95B97, Dowling, and Jackson). Percentage of loss of chlorophyll in the susceptible checks was ≈40%; Jackson and Dowling had a significantly lower percentage loss (13 and 16%, respectively) compared with the susceptible checks. The percentages of chlorophyll loss of K1621, K1639, and Pioneer 95B97 were not statistically different from the percentage of loss of Jackson.
[Show abstract][Hide abstract] ABSTRACT: The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is a major pest of soybean, Glycine max (L.) Merr. Since 2000, when A. glycines was detected in the United States, several studies on this insect have been done in different areas, but there is no report of any studies of stylet penetration behavior by A. glycines on resistant and susceptible soybean. Assessment of feeding behavior of this aphid species was compared on four resistant entries (K1639, Pioneer 95B97, Dowling, and Jackson) and a susceptible check (KS4202) by using the electrical penetration graph (EPG) technique. Feeding behavior of A. glycines adults was recorded during a 9-h period. The average time needed to reach the first sieve element phase by A. glycines was 3.5 h in KS4202, whereas it was 7.5 h in the resistant entries. The total duration in the sieve element phase was longer than an hour in KS4202, and only 2 to 7 min in the resistant entries. These results suggest that morphological or chemical factors in the phloem tissue of resistant plants affect stylet penetration activities of A. glycines. In the majority of the recordings, however, the aphid stylet reached the xylem phase before penetrating the sieve element, and the time that aphids spent ingesting xylem sap was not different among all entries. Therefore, it is possible that xylem sap in the resistant entries may contain toxic substances that change aphid behavior and that affect further activities in the sieve element phase.
[Show abstract][Hide abstract] ABSTRACT: The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is an introduced pest of soybean, Glycine max (L.) Merr., in North America, and it can reduce yields by 50%. Since 2000, when A. glycines was first detected in the United States, studies of this insect and possible control methods have been initiated. Plant resistance to this aphid species is one important component of integrated control. Reproduction of A. glycines was compared on 240 soybean entries in a pesticide-free greenhouse. Eleven entries had fewer nymphs produced, compared with the susceptible checks, and these entries were used in follow-up experiments to assess antibiosis and antixenosis. Antibiosis was estimated in true no-choice tests, in which adults were confined individually in double-sided sticky cages stuck to the upper side of leaves. Antixenosis was assessed in choice tests, in which all entries were planted in a single pot. Adult aphids were placed in the center of the pot, and 24 h later the number of adults on each plant was counted. Of the 11 entries evaluated, nine showed a moderate antibiotic effect to A. glycines, and the other two entries (K1639 and Pioneer 95B97) showed not only a strong antibiotic effect but also exhibited antixenosis as a category of resistance to A. glycines. The resistant soybean entries found in this work are potential sources for A. glycines control.
RESUMEN El áfido de la soya, Aphis glycines Matsumura, es una plaga introducida de la soya, Glycine max (L.) Merr., en Norte América y puede causar pérdidas en rendimiento hasta en un 50%. Se iniciaron estudios de este insecto y posibles métodos de control desde el año 2000, cuando fue detectado en los Estados Unidos. La Resistencia de plantas es un importante método de control en el manejo integrado contra este áfido. La reproducción de A. glycines fue comparada en 240 genotipos de soya en condiciones de invernadero libre de pesticidas. Once genotipos presentaron un número más bajo de ninfas que los testigos susceptibles y fueron usados en subsiguientes experimentos para detectar antibiosis y antixenosis. La antibiosis fue determinada por medio de experimentos de no-selección, donde adultos fueron confinados individualmente en pequeñas jaulas de doble faz pegadas sobre el haz de las hojas. La antixenosis fue estimada por medio de experimentos de libre selección, en los que diferentes genotipos fueron sembrados en un mismo recipiente. Los adultos fueron colocados en el centro del recipiente y el número de adultos en cada planta fue contado 24 horas después. De los 11 genotipos estudiados, nueve mostraron un moderado nivel de antibiosis al insecto, y los otros dos (K1639 y Pioneer 95B97), no sólo presentaron un alto nivel de antibiosis, sino que fueron los únicos genotipos que exhibieron antixenosis como categoría de resistencia. Los genotipos resistentes encontrados en este trabajo son potenciales fuentes de resistencia para controlar A. glycines.
[Show abstract][Hide abstract] ABSTRACT: Genetic linkage maps are fundamental for the localization of genes conferring tolerance to greenbug, Schizaphis graminum (Rondani), feeding damage in sorghum, Sorghum bicolor (L.) Moench. Thirteen linkage groups (LGs) containing 60 simple sequence repeat (SSR) loci were mapped by using a set of sorghum recombinant inbred lines (RILs) obtained from the cross '96-4121' (greenbug-tolerant parent) x Redlan (greenbug-susceptible parent). The LG spanned a distance of 603.5 cM, with the number of loci per LG varying from 2 to 14. Seventeen additional SSR loci were unlinked at a log of odds value of 3.0. Based on chlorophyll loss occurring after greenbug feeding, visual damage ratings, and soil plant analysis development (SPAD), chlorophyll-loss indices were recorded for each RIL and for the parents used in the cross. Composite-interval mapping identified three quantitative trait loci (QTLs) associated with biotype I and five QTLs associated with biotype K. The amount of phenotypic variation explained by these QTLs ranged from 9 to 19.6%. The identification of QTLs that influence greenbug tolerance will not only facilitate the use of marker-assisted selection in sorghum breeding programs but also will provide a solid foundation for detailed characterization of individual loci implicated in greenbug tolerance in sorghum.