1. 1. Clark, A. J., and K. L. Perry. 2002 Transmissibility of field isolates viruses by Aphis glycines. Plant Dis. 86: 1219-1222. 2. Deol, G.S., J.C. Reese, B.S. Gill. 1997. A rapid, nondestructive technique for assessing chlorophyll loss from greenbug (Homoptera: Aphididae) feeding damage on sorghum leaves. J. Kans. Entomol. Soc. 70: 305-312. 3. Hill, C. B., Y. Li, and G. L. Hartman. 2004. Resistance to the soybean aphid in soybean germplasm. Crop Sci. 44: 98-106. 4. Kilgore, G. L., and D. L. Fjell. 1997. Growth and development of the soybean plant. Soybean Production Handbook, Kansas State University. March. P. 3. 5. (NCPMC) North Central Pest Management Center. 2000. Soybean Aphid, Aphis glycines Matsumura. Regional Pest Alert, USDA, CSREES, NCPMC, NC-502. 2 p. 6. Ostlie, K. 2002. Managing Soybean Aphid. University of Minnesota, St. Paul, MN. (http://www.soybeans.umn.edu/crop/insects/aphid/aphid_publication_managingsba.htm) 7. SAS Institute Inc. 1999. Version 8, SAS institute. Cary, NC, USA. 8. Sloderbeck, P. E., J. C. Reese, R. J. Whitworth, C. M. Smith, R. A. Higgins, W. T. Schapaugh, R. E. Wolf and D. J. Jardine. 2003. The Soybean Aphid. Kansas State University Agricultural Experiment Station and Cooperative Extension Service. MF-2582 We thank Sonny Ramaswamy, C. Michael Smith for advice. Additionally we thank The Kansas Soybean Commission and Pioneer Hi-Bred International for providing soybean entries and funding. In experiment I, the SPAD values measured in the leaves (no infested and infested) of the entries KS4202, 93B15, K1642, and K1613 were statistically (P < 0.001) different (Table 2). In the experiment II, the SPAD values were different (P < 0.001) only in the two susceptible checks KS4202 and 93B15 (Table 2). Although, K1642 and K1613 along with the susceptible checks had the highest SPAD indices compared to the other entries in both experiments (Fig. 3). The average SPAD index of all the entries in both experiments was 0.27. Not only PHIAG072, K1621, Dowling, K1639, and Jackson are resistant to A. glycines, but also had less reduction in their chlorophyll content and were below the average SPAD index (Fig. 3), indicating that these entries could develop all their potential with minimum controls against A. glycines. CHLOROPHYLL LOSSES CAUSED BY THE SOYBEAN APHID, Aphis glycines Matsumura (HOMOPTERA: APHIDIDAE) ON DIFFERENT SOYBEAN ENTRIES John Diaz-Montano 1,2, John C. Reese 2, William T. Schapaugh 3, and Leslie. R. Campbell 2 1 jdm@ksu.edu, 2 Department of Entomology, Kansas State University, Manhattan, KS 66506, 3 Department of Agronomy, Kansas State University, Manhattan, KS 66506 The soybean aphid, Aphis glycines, is an introduced pest of soybeans, Glycine max (L.) Merr. in North America. Since 2000 when the soybean aphid was first detected in the US, studies of this insect and possible control methods have been initiated. A. glycines populations increase quickly, spread very rapidly, cause severe damage and may reduce yields by 50%. A. glycines also vectors viral diseases such as soybean mosaic virus. We studied soybean resistance to the soybean aphid on more than 200 entries, and few entries showed some levels of antibiosis and antixenosis as categories of resistance to the soybean aphid. These entries, along with the susceptible checks KS4202 and 93B15, were selected for studying the chlorophyll losses caused by the soybean aphid in a true no-choice test, in which aphids were confined in double-sided sticky cages placed to the upper side of leaves. We developed a protocol using the susceptible check KS4202. Zero, Five, 10, 20, 30 and 40 aphids were confined in the cages and after four and seven days of infestation the chlorophyll content was measured using the SPAD chlorophyll meter. Chlorophyll measurements were statistically different between the treatments with 30 and 40 aphids confined for seven days. However, there were not differences in chlorophyll content between infested and non-infested plants within any of the treatments. Additional experiments are being conducted with increasing the numbers of days of confinement to confirm differences in chlorophyll content within treatments. ABSTRACT The soybean aphid, Aphis glycines Matsumura (HOMOPTERA: APHIDIDAE), is a pest of soybeans, Glycine max (L.) Merr. in the United States since 2000 (5). High populations can cause severe damages and yield losses up to 50% (6), is the only aphid that develops large colonies on soybeans in North America (8), and vectors several viral diseases such as soybean mosaic virus (1). Host plant resistance is a very important component of an IPM program, and the tolerance category of host plant resistance places no selection pressure on the aphid population for more virulent biotypes. The objectives of this work were to determine the number of days and aphids needed to observe chlorophyll losses and to compare reduction of chlorophyll content on resistant and susceptible soybean entries, in order to quantify tolerance to soybean aphid feeding damage. INTRODUCTION Analysis of variance for SPAD values and Indices were conducted using Proc General Linear Models (GLM). Multiple comparisons were computed using Tukey’s Studentized Range Test (7). Statistical Analyses There were no statistical differences between the SPAD values measured on the no-infested and infested leaves in the test 1 (P = 0.38), test 2 (P = 0.49) or test 3 (P = 0.78) (Table 1). In the test 4 statistical differences (P < 0.001) were observed among the SPAD values taken from leaves with 30 and 40 aphids confined for seven days, but there were no differences of the SPAD values measured from no-infested and infested leaves within each treatment. Only, in the test 5 differences (P < 0.001) were detected in the chlorophyll content measured from no-infested and infested areas. SPAD indices range from zero (no loss of chlorophyll) to one (total loss of chlorophyll) (2). In the tests 1, 2, 3 and 4 the indices were very low (0.03 to 0.17), whereas, SPAD indices in test 5 were 0.45 indicating an important loss of chlorophyll caused by 30 to 40 aphids confined for 10 days. RESULTS AND DISCUSSION Timing and infestation rates Chlorophyll losses on different soybean entries Chlorophyll losses caused by A. glycines were not easily detected. After several experiments with different number of days (four, seven and 10) and adult aphids confined (five, 10, 20, 30 and 40), 30 to 40 aphids confined for 10 days caused differences in the chlorophyll content on the leaves of a susceptible check. PHIAG072, K1621, Dowling, K1639, and Jackson, found as highly resistant in previous work, showed the least chlorophyll losses compared to the other entries. ACKNOWLEDGEMENTS Plants (susceptible check KS4202) were infested when they reached the V-1 stage (two fully developed leaves at unifoliate nodes) (4). Two double-sided sticky cages (Converters, Inc., Huntingdon Valley, PA, USA), with inner oval area of 1.2 cm 2, were fixed to the upper side of each leaf using steel clips were covered with a organdy cloth (Fig.1). One cage was infested (I) and the other no- infested (NI). Test 1: five, 10, and 20 aphids confined for four days (5 Rep.) Test 4: 30 and 40 aphids confined for seven days (3 Rep.) Test 2: 5, 10, and 20 aphids confined for seven days (5 Rep.)Test 5: 30 to 40 aphids confined for 10 days (3 Rep.) Test 3: 30 and 40 aphids confined for four days(3 Rep) The chlorophyll content was measured using the SPAD chlorophyll meter (Minolta, Japan) (Fig. 2). A SPAD index (2) was calculated using the following formula: SPAD Index: (NI-I)/NI, where NI, is no-infested area, and I, is infested area Two comparable experiments were performed on seven soybean entries resistant to A. glycines. The entries were K1613, K1621, K1639, K1642 (Property of Kansas State University), PHIAG072 (Property of Pioneer ® ), and Dowling and Jackson found resistant to A. glycines (3). Along with KS4202, the genotype 93B15 was included as a second susceptible check. There were three replications per each entry. The treatment used was 30 aphids confined for 10 days. MATERIALS AND METHODS Timing and infestation rates REFERENCES CONCLUSIONS Number of Aphids Confined 510203040 Chlorophyll Content (4 days) Test 1Test 3 SPAD Value (NI)37.8 ± 1.1 a36.3 ± 3.7 a38.1 ± 2.0 a30.4 ± 3.6 a28.8 ± 4.9 a SPAD Value (I)36.8 ± 3.1 a34.7 ± 4.8 a35.0 ± 1.5 a28.0 ± 4.6 a26.7 ± 4.7 a SPAD Index0.03 ± 0.070.04 ± 0.100.08 ± 0.030.08 ± 0.050.07 ± 0.01 Chlorophyll Content (7 days) Test 2Test 4 SPAD Value (NI)31.6 ± 5.2 a34.0 ± 0.6 a33.3 ± 1.8 a 21.1 ± 1.4 bc26.8 ± 1.1 a SPAD Value (I)30.0 ± 5.5 a32.2 ± 1.6 a31.5 ± 1.7 a17.5 ± 1.6 c 24.4 ± 1.9 ab SPAD Index0.05 ± 0.04 0.17 ± 0.030.09 ± 0.03 Chlorophyll Content (10 days) Test 5 SPAD Value (NI)19.1 ± 4.0 a 17.0 ± 1.9 ab SPAD Value (I) 10.6 ± 2.6 bc 9.2 ± 2.8 c SPAD Index0.45 ± 0.070.45 ± 0.22 Means followed by different letter in a test are significantly different (P <0.05, Tukey’s test) Table1. Mean chlorophyll content (SPAD Values) and SPAD indices in the susceptible check KS4202 after confinement of aphids for four, seven and 10 days Chlorophyll Content (SPAD Value) Experiment IExperiment II EntryNII I KS420225.2 ± 5.1 a14.3 ± 2.6 ef29.4 ± 2.7 a18.7 ± 3.8 bcd 93B1524.2 ± 3.5 ab14.5 ± 2.7 def27.0 ± 0.9 ab16.7 ± 1.3 cd K164223.4 ± 1.6 abc12.9 ± 1.6 f24.8 ± 3.7abc17.0 ± 3.1 bc K161322.6 ± 2.5 abcd13.7 ± 1.8 f25.8 ± 3.7 abc17.5 ± 2.0 bcd K162122.4 ± 6.4 abcde16.8 ± 2.0 bcdef23.0 ± 3.5 abcd17.7 ± 2.5 bcd PHIAG07220.9 ± 1.2 abcdef15.9 ± 1.4 cdef24.0 ± 1.4 abcd19.4 ± 0.6 bcd Dowling20.9 ± 1.3 abcdef16.6 ± 2.3 bcdef20.3 ± 4.2 abcd17.0 ± 6.0 cd K163920.5 ± 1.5 abcdef16.6 ± 1.6 bcdef22.5 ± 5.2 abcd19.0 ± 1.6 bcd Jackson16.3 ± 1.7 bcdef13.8 ± 0.6 f16.6 ± 2.4 cd14.5 ± 3.0 d Table 2. Mean chlorophyll content (SPAD Value) in several soybean entries after confinement of 30 adult aphids for 10 days Means followed by different letter in a column are significantly different (P <0.05, Tukey’s test) Fig. 3. Chlorophyll losses (SPAD Index) in several soybean entries after confinement of 30 adult aphids for 10 days x = 0.27 Entry SPAD Index Fig. 1 Fig. 2 Chlorophyll losses on different soybean entries