[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.
Full-text · Article · Oct 2013 · Journal of Economic Entomology
[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.
Full-text · Article · Feb 2012 · Journal of Plant Registrations
[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.
Full-text · Article · Dec 2011 · Journal of Economic Entomology
[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.
[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.
Full-text · Article · Nov 2007 · Journal of Economic Entomology
[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.
Full-text · Article · Nov 2006 · Journal of Economic Entomology
[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.
Full-text · Article · May 2005 · Journal of Economic Entomology
[Show abstract][Hide abstract] ABSTRACT: Greenbug, Schizaphis graminum (Rondani), (Homoptera: Aphididae), biotype K feeding reduced the chlorophyll content and photosynthetic rate on both resistant ('Cargill 607E') and susceptible ('NC+ 272') sorghum hybrids. Greenbugs caged on a 5 cm × 2.5 cm area on the newest fully expanded leaves for one day caused greater reduction of photosynthetic rate and chlorophyll content loss in the susceptible line compared to the resistant line. The resistant hybrid recovered more rapidly than the susceptible hybrid over a 10-day observation period. However, high levels of four day feeding damage caused a drastic decrease in chlorophyll content and photosynthetic rate in both resistant and susceptible hybrids and little recovery was recorded. Thus, 'Cargill 607E' was physiologically tolerant to greenbug feeding at low levels of infestation. These data could be helpful in predicting yield losses if the relationship between photosynthetic rate and yield is well understood.
No preview · Article · Oct 2002 · Journal of the Kansas Entomological Society
[Show abstract][Hide abstract] ABSTRACT: The effect of greenbug, Schizaphis graminum (Rondani) feeding on chlorophyll content and photosynthetic rate in sorghum [Sorghum bicolor (L.) Moench] was assessed under artificial light conditions. Between 1500-1750 greenbugs were used to infest a 5 cm × 2.5 cm area on a sorghum leaf by means of a modified double-sided sticky cage. A treatment with cage only on the leaf was also included. The control treatment was leaves with no cages and no greenbugs, which would allow measurement of parameters absent the internal effects of either greenbug feeding or cages. Greenbug infestation intervals of 1, 2, 3 and 4 days reduced significantly both photosynthetic rate and chlorophyll content. Photosynthetic rate showed a positive correlation with chlorophyll content (r = 0.36, d.f. = 208, P = 0.0001). With a small drop in chlorophyll content, a drastic reduction in photosynthetic rate was noticed. Decreased chlorophyll content due to greenbug feeding partially explained the reduction in photosynthetic rate. Leaf age, nutritional status, and micro-environmental parameters may also have influenced the relationship between photosynthetic rate and chlorophyll content.
No preview · Article · Apr 2002 · Journal of the Kansas Entomological Society
[Show abstract][Hide abstract] ABSTRACT: Studies were conducted using a chlorophyll meter (SPAD-502, Minolta Corporation, Ramsey, NJ) to estimate chlorophyll loss in wheat leaves caused by feeding damage from Russian wheat aphids, Diuraphis noxia (Mordvilko) and greenbugs. Schizaphis graminum (Rondani). A SPAD Index was calculated as the chlorophyll loss in SPAD units (SPAD meter reading for uninfested tissue - SPAD meter reading for infested tissue), dividing by the SPAD meter reading for uninfested tissue. Thus, the larger the value for the SPAD Index, the greater the proportional loss of chlorophyll for that treatment. Russian wheat aphids and greenbugs were allowed to feed on wheat leaves for periods of 1 to 10 days. For Russian wheat aphids, chlorophyll loss increased gradually as the duration of the feeding period increased (i.e., up to 10 days). However, for greenbugs, chlorophyll loss increased more quickly up to the 4th day of feeding, and then remained relatively constant. Overall chlorophyll loss was greater from greenbugs than from Russian wheat aphids, suggesting greater feeding damage by greenbugs. This SPAD meter technique could be used to screen wheat germplasm for resistance to greenbugs.
No preview · Article · Oct 2001 · Journal of the Kansas Entomological Society