Could the Desmodium ‘push-pull’system for Striga control in Africa work on Phelipanche ramosa and Orobanche crenata?

Mohamed Shrif • Alistair Murdoch • Irene Mueller-Harvey

DESMODIUM

PUSH

MAIZENapier Desmodium Maize

Pho

to b

y S

am

Njih

ia, K

AR

I, Ke

nya

Push-pull habitat management system designed for control of maize stem borer

Plot sizes: 15 x 15 to 50 x 50 metres

System developed by Khan and co-workers at ICIPE in Kenya

NAPIER

PULL

The push-pull strategy in the field

Photo from Francis Muyecko, KARI, Kenya

SERENDIPITY!

“But my main problem is NOT

stem borer, it’s Striga” “And mine is

actually Orobanche/

Phelipanche”

Objectives

• To determine whether this ‘push-pull’ control

system developed by ICIPE in Western Kenya using

Desmodium intortum (Silverleaf) and D. uncinatum

(Greenleaf), could be adapted to control

Phelipanche and Orobanche

• Results here for two Greek seed lots (D1 and D6) of

Phelipanche ramosa kindly supplied by Falia

• Results not presented today on Orobanche crenata

and also for Striga hermonthica.

Experimental system

Reading University, 2009/10

Lower pots

Host plants of Striga (Millet), Pea for O.crenataand Tomato for Phelipanche ramosa

Upper pots

Desmodium Greenleaf or Desmodium Silverleaf

Tom

atoTube Tube

Desmodium

Phelipanche ramosa

No

Desmodium

Shoots per pot LSD (P=0.05) = 32.80

P.

ram

osa

D1

Sil

verl

eaf

+ D

1

Gre

en

leaf

+ D

1

P.

ram

osa

D6

Sil

verl

eaf

+ D

6

Gre

en

leaf

+ D

6

Shoots of P.ramosa

parasitising tomato

Shoot dry weight per pot , mg LSD (P=0.05) = 4.1 mg

P.

ram

osa

D1

Sil

verl

eaf

+ D

1

Gre

en

leaf

+ D

1

P.

ram

osa

D6

Sil

verl

eaf

+ D

6

Gre

en

leaf

+ D

6

Dry weight of shoots of P.ramosa

(D1 & D6) parasitising tomato

Flavonoid compounds affecting

Striga hermonthica

From Pickett, Hamilton, Hooper, Khan and Midega (2010) Ann. Rev. Phytopathol. 2010.48:161-

177

B A

HPLC trace• Dual action

A. Germination stimulation

B. Inhibition of subsequent growth

• Overall effects

– reduced attachment to host

– suicidal germination

Germination stimulationInhibition ofsubsequent growth

Attachments (in vitro) study using conditioned and GR24-stimulated P. ramosa seeds and Desmodium

greenleaf exudates at a range of concentrations

So far so good

Now for

the bad news!

LSD, P=0.05

Height, cm, of tomato 14 weeks after planting

Co

ntr

ol

Sil

verl

eaf

Gre

en

leaf

P.

ram

osa

D1

Sil

verl

eaf

+ D

1

Gre

en

leaf

+ D

1

P.

ram

osa

D6

Sil

verl

eaf

+ D

6

Gre

en

leaf

+ D

6

Negative effects of Desmodium

and P. ramosa on tomato

Treatment Height Shoot weight Fruit weight

Tomato only 120 cm 55 mg 31 mg

Desmodium

uncinatum (Silverleaf)- 19% - 39% - 68%

Desmodium intortum

(Greenleaf)- 21% - 38% - 62%

P. ramosa seed lot D1 - 25% - 43% - 39%

P. ramosa seed lot D1

+ Silverleaf- 48% - 69% - 36%

P. ramosa seed lot D1

+ Greenleaf- 36% - 69% - 81 %

LSD (%) P = 0.05 8 % 13% 6%

• Both Desmodium species effectively reduced the

number and dry weight of Ph. ramosa shoots parasitising

tomato

• Ph. ramosa seed lot D1 was affected by the Desmodium

more than D6

• Desmodium, however, reduced tomato height and yield

So sorry, the answer to the question posed is yes

and no

Conclusions

Our grateful thanks to the government of Libya for a scholarship to Mohamed Shrif

To Laurence Hansen and Caroline Hadley for technical assistance (Plant Environment Laboratory),

To Ron Brown (Chemistry& Biochemistry Laboratory) for their technical assistance

Acknowledgements