College Station July 2006

College Station October 2006

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 A&M University, Lubbock, TX

1 2 3 4 5

6 7 8 9 10

11 12 13 14 15

20 16 17 18 19

Picture No.

Soil testedNematode population

(vermiform/gram)Percent of

Fibermax 832Percent

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.

** 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.

Preliminary Test Rio Grande Valley 1999

0

500

1000

1500

2000

2500

3000

S1 S2 S3 S4 S5 S6

LSD0.05 non-treated

autoclaved

Soils

Reproduction of Rotylenchulus reniformis under cotton after 14 weeks in non-treated or autoclaved portions of six soils in a greenhouse trial (LSD for treatment*soil).

Fin

al n

em

ato

de

po

pu

latio

n

(ne

m/1

00

cm

3)

Oil Well Field

Nogales Field

Brush Area

Levy Wieden Field

0-30 cm North Farm

45-105 cm North Farm

0

1

2

3

4

5

S1 S2 S3 S4 S5 S6

LSD0.05 non-treated

autoclaved

Soils

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 treatment*soil).

Fre

sh r

oo

t w

eig

ht

(g)

Oil Well Field

Nogales Field

Brush Area

Levy Wieden Field

0-30 cm North Farm

45-105 cm North Farm

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 1:20 (July test) or 1:10 (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.

Soil typeNematode 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*