Annual Report of Progress
to the
MISSISSIPPI SOYBEAN PROMOTION BOARD
for 1998

Objectives

1. Examine soybean cultivars and breeding lines for resistance to the reniform nematode. 
2. Demonstrate the yield losses that can be expected when soybeans are planted in a reniform infested field.

Significant Accomplishments

Nineteen Soybean varieties representing maturity group IV-VI were planted in a field located in Inverness, Mississippi that was naturally infested with the reniform nematode. Each variety was planted with and without the nematicide Temik 15G at 5.01 lb formulated material per acre. Soybean yields varied in their responses to the Temik 1 5G application. Six varieties did not result with an increase in yield with the use of the nematicide.

Five soybean varieties were included in maturity groups IV (Table 1). Soybean yields ranged from 60.6 bu/acre to 74.3 in HBK-4755 and NKS-5100, respectively, in reniform infested soil. The addition of Temik 15G resulted in an increase in soybean yields with all MG IV varieties except NKS-5100 and RVS-490. Temik 15G improved the yield of AP-4880, HBK-4755 and P-9511 by 0.1, 1.9and0.3bu/acre.

Eleven soybean varieties were included in maturity group V (Table 2). Soybean yields ranged from 46.9 bu/acre to 59.2 bu/acre in RVS-77 and A-5959 respectively. The addition of Temik 15G resulted in an increase in yields for six MG V soybeans. The yield of DPL-5354 was increased 3.7 bu/acre with Temik 15G.

Three soybean varieties were included in maturity group VI (Table 3). Soybean yields ranged from 39.6 bu/acre to 49.6 bu/acre in RVS-678 and S-62-62 respectively. The addition of Temik 15G resulted an increase in the yields of all MG VI varieties. The yield of S-62-62 was improved 6.2 bu/acre with Temik 15G.

Reniform nematode population development varied with the specific soybean variety. The final nematode counts were in general higher in the Temik 15G treated plots compared with the untreated varieties (Table 4, Table 5 and Table 6). The fact that nematode populations are higher on some of the Temik 15G treated varieties is not uncommon in nematology research. This suggests that the particular variety may be susceptable to nematode infection and allowed rapid nematode development but tolerant to the nematode damage. The only definitive measure for resistance would come from the greenhouse evaluations.

The nineteen varieties planted in replicated field were also examined in the greenhouse for nematode disease ratings (Table 7, Table 8, Table 9). Only the varieties were actually resistant to the reniform nematode. These were RVS - 529i, DPL 5644 rr and DPL 5806 rr. These varieties will actually reduce nematode numbers when planted in an infested field.

Thirty additional varieties were examined in replicated greenhouse studies for reniform disease ratings (Table 10, Table 11 and Table 12). Two cultivars, in maturity groups IV, FFR 467 rr, and on maturity group V, TV-5466 rr were considered resistant.

Ninety additional varieties are currently in various stages of progress. Each test requires a minimum of 90 days for evaluations therefore are harvested and evaluated at various intervals during the year.

Publications

1. Lawrence, G.W. and K.S. McLean. 1998. Response of mid-south soybean varieties to the reniform nematode. Journal of Nematology 30: In press.
2. Lawrence, G.W. and K.S. McLean. 1998. Plant-parasitic nematode pests of soybean in L.G. Heatherly and H.F. Hodges Eds. Soybean Production in the mid-south. CRC Press, Washington, D.C.
   
   

Soybeans in Mississippi Mississippi Agricultural and Forestry Experiment Station  Mississippi State University Extension Service Division of Agriculture, Forestry and Veterinary Medicine

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