Annual Report of Progress
to the
MISSISSIPPI SOYBEAN PROMOTION BOARD
for 1997

Objectives

1. Examine soybean cultivars and breeding lines for resistance to the reniform nematode.
   
2. Demonstrate the yield losses that can be expected when soybean 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.O lb formulated material per acre. Soybean yields varied in their responses to the Temik 15G application. Only two varieties did not result with an increase in yield with the use of the nematicide.

Six soybean varieties were included in maturity groups IV (Table 1). Soybean yields ranged from 46.73 bu/acre to 65.36 in A 4715 and DX 478, respectively, in reniform infested soil. The addition of Temik 15G resulted in an increase in soybean yields with all MG IV varieties except A 4715. Temik 15G improved the yield of DPL 3478, A 4922 and DX 478 by 6.22, 3.30 and 2.81 bu/acre.

Nine soybean varieties were included in maturity group V (Table 2). Soybean yields ranged from 57.4 bu/acre to 71.1 bu/acre in RVS 549 and P 9594 respectively. The addition of Temik 15G resulted in an increase in yields for all MG V soybeans. The yield of S-59-60 was increased 8.1 bu/acre with Temik 15G.

Four soybean varieties were included in maturity group VI (Table 3). Soybean yields ranged from 58.7 bu/acre to 64.3 bu/acre in P9631 and DPL 3640 respectively. The addition of Temik 15G resulted an increase in the yields of all MG VI varieties except DPL 3640. The yield of P 9631 was improved 7.8 bu/acre with Temik I 5G.

Reniform nematode population development varied with the specific soybean variety. The final nematode counts were in general lower in the Temik 15G treated plots compared with the untreated varieties. The fact that nematode populations were higher on some of the Temik 15G treated varieties is not uncommon in nematology research. This suggests that the particular variety may be susceptible to nematode infection and allowed repid 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 the field study were also planted in the greenhouse for nematode disease ratings. Three separate studies were conducted, however. Nematode reproduction on selected control plants was low which may result in the erroneous assignment of a disease ratings to a particular variety. The test is currently in progress to accurately assess nematode disease ratings to each variety.

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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