College Station July 2006

1
Evaluation of Soil from Selected Sites for
Suppressiveness against the Reniform
Nematode A.F. Robinson1 J.M. Bradford2, S.M.
Greenberg2, C. Overstreet3, G.B. Padgett4, S.R.
Stetina5, A. Westphal6, and T.A.
Wheeler7 1USDA-ARS, College Station, TX,
2USDA-ARS, Weslaco, TX, 3LSU AgCenter, Baton
Rouge, LA, 4LSU AgCenter, Winnsboro,
LA, 5USDA-ARS, Stoneville, MS, 6Purdue Univ.,
West Lafayette, IN, 7Texas AM University,
Lubbock, TX
Experimental Soil was collected from cotton
fields in Louisiana, Mississippi, and South Texas
where the reniform nematode (Rotylenchulus
reniformis) was present at lower population
densities than expected based on soil texture,
cropping history, and infestation levels in
nearby fields. In preliminary tests conducted in
the Rio Grande Valley in 1999, soil was
autoclaved (gray bars) for 30 minutes on 2
consecutive days, or not autoclaved (white bars),
placed directly into greenhouse pots and planted
to susceptible cotton for 14 weeks. In tests
conducted at College Station in 2006, soil was
mixed 120 (July test) or 110 (October test)
with a fine sand supplemented with vermiculite
and balanced nutrients, and placed within 0.5
liter pots that were planted to susceptible
cotton cv. Fibermax 832. Two weeks after
planting, each pot was inoculated with 4,000
vermiform R. reniformis, and 7 weeks after
inoculation, three cores were removed from each
pot to evaluate nematode populations in pots.
Nematode population densities were measured by
counting vermiform stages collected by Baermann
funnel extraction.
Results In 1999, autoclaving greatly increased
final nematode populations for all sites except
the brush area. Root biomass differences were
too small to explain the effect. In 2006,
transferable agent(s) in soil from eight fields
suppressed populations measurably (P 0.05).
Strong suppression (36-95) was obtained with
soil from North Farm. Surface soil (0-15 cm)
from the North Farm suppressed populations 95 in
the second test, compared with 91 for the
resistant control, G. barbadense GB-713
population suppression values measured for North
Farm surface soil in the 1999 and July 2006 test
were 90 and 80 respectively. Suppression
values for deeper soil from North Farm in the
1999, and the July and October tests of 2006 were
95, 36, and 38. Conclusion Our results
indicate the presence of a transferable agent in
North Farm soil that suppresses R. reniformis at
higher concentrations in the top 30 cm than below
30 cm. The level of suppression observed in one
test was comparable to that obtained with one of
the best sources of host plant resistance within
Gossypium. Suppression in upper soil layers at
North Farm is consistent with numerous previous
observations of greater nematode populations deep
in the soil than near the surface at this site.
Further research is merited.
College Station July 2006
Preliminary Test Rio Grande Valley 1999
Soil type Nematode population (vermiform/gram of soil) Percent of Fibermax 832 Percent suppression
Lubbock Station 181 191 -90
Lamesa 79 83 18
Panhandle 56 59 42
North Farm, 23-36 cm 61 64 36
North Farm, 0-15 cm 19 20 80
USDA at Stoneville 36 38 62
Fibermax 832 95 100 0
GB713 22 23 77
6 replicates per treatment
No treatment means significantly differ from Fibermax 832 No treatment means significantly differ from Fibermax 832 No treatment means significantly differ from Fibermax 832 No treatment means significantly differ from Fibermax 832
Final nematode population (nem/100 cm3)
Fresh root weight (g)
Brush Area
0-30 cm North Farm
45-105 cm North Farm
Oil Well Field
Nogales Field
Levy Wieden Field
Oil Well Field
Nogales Field
Brush Area
Levy Wieden Field
0-30 cm North Farm
45-105 cm North Farm
Cotton root fresh weight after 14 weeks in
Rotylenchulus reniformis infested non-treated or
autoclaved portions of six soils in a greenhouse
trial (LSD for treatmentsoil).
College Station October 2006
Picture No. Soil tested Nematode population (vermiform/gram) Nematode population (vermiform/gram) Nematode population (vermiform/gram) Percent of Fibermax 832 Percent of Fibermax 832 Percent suppression Percent suppression
1 11D 306 312 104
2 Sweet Potato, NE Louisiana 387 129
3 St. Joe, Louisiana Gin Ridge North East Research Station 272 91
4 Panhandle Field, 0-6 157 52 48
5 Rapides Parish, Bill Poole Farm, Field BP-1, 06-47 178 39 41
6 Morehouse Parish, Boyd Holley Farm, Field-Big Cat, 05-2695 189 63 37
7 Rapides Parish, Bill Poole Farm, Field PV, 06-33 101 34 66
8 Morehouse Parish, B. Turner Farm, Field 104, 06-1154 162 54 46
9 Rapides Parish, Dean Lee Research Station, Sweet Potato, 06-1148 287 96
10 East Baton Rouge, Burden Plantation, May 14, 2006 226 75
11 Rapides Parish, Bill Poole Farm, Field RB-3, 06-53 209 70
12 Rapides Parish, Bill Poole Farm, Field JP, 06-55 147 49 51
13 Concoudia Parish, VanGilden Farm, Field P14-1, 06-197 424 141
14 Franklin Parish, Ken Thornhill Farm, Field Test 201, 06-1182 330 110
15 Russ Hayes 198 66 34
16 North Farm, 23-38 cm 212 71
17 North Farm, 0-15 cm 14 5 95
18 USDA at Stoneville 307 102
19 Fibermax 832, susceptible control, no supplement 324 108
20 Fibermax 832, susceptible control, extra set of 6 reps 275 92
N/A GB713, resistant control, no supplement 27 9 91
N/A Delta Pine 16, extra susceptible control, 6 reps 347 116
6 replicates per treatment Denotes means significantly differ from Fibermax 832 at P 0.05. 6 replicates per treatment Denotes means significantly differ from Fibermax 832 at P 0.05.
Denotes means significantly differ from Fibermax 832 at P 0.01. Denotes means significantly differ from Fibermax 832 at P 0.01.
Plants at the end of the experiment. No obvious
plant growth suppression for any treatment.