(±)-Catechins inhibit prehaustorium formation in the parasitic weed Phelipanche ramosa and reduce tomato infestation

Abstract

Background: Phelipanche ramosa L. (Pomel) is a noxious parasitic weed in field and vegetable crops in Mediterranean countries. Control of this pest is complex and far from being achieved, and new environmentally-friendly strategies are being sought. The present study evaluates the possibility of using (±)-catechins as a natural herbicide against broomrapes.

Results: The results show that (±)-catechins have no effect on GR24-induced germination over a wide concentration range (10^-4 to 10^-10 m), nor on radicle elongation after germination, but strongly inhibit, at 10^-4 and 10^-5 m, prehaustorium formation in response to the haustorium-inducing factor, cis/trans-zeatin. Accordingly, pot experiments involving the supplies of 10^-5 m of (±)-catechins to tomato plants infested or not with P. ramosa demonstrate that (±)-catechins do not influence growth of non-parasitized tomato plants and prevent heavy infestation by strongly reducing parasite attachments and inducing parasite necrosis once they are attached.

Conclusion: This study points the potential use of (±)-catechins for parasitic weed control. It raises also the question of the mechanisms involved in the inhibition of prehaustorium formation and the necrosis of parasite attachments in response to (±)-catechins application. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Keywords: allelopathy; biological control; haustorium; plant–plant interaction.

Figure 1

Early developmental stages of Phelipanche ramosa. (A) Conditioned seeds, (B) germinated seeds, (C) germinated seeds with papillae at the root apex, as prehaustorium (arrow), (D) parasite attachments (arrow, tubercles) to tomato root (TR).

Figure 2

(±)‐Catechins have no effect on Phelipanche ramosa seed germination. (A) Conditioned seeds were treated with 10⁻⁹  m GR24 (in 0.02% (v/v) acetone) as germination stimulant. (B) Conditioned seeds were treated with 10⁻⁹  m GR24 as germination stimulant in the presence of 10⁻⁵  m (±)‐catechins (in 0.02% (v/v) acetone). Photographs were taken 15 days after treatment.

Figure 3

(±)‐Catechins have no effect on radicle elongation of Phelipanche ramosa germinated seeds. Conditioned seeds were treated with 10⁻⁹  m GR24 as germination stimulant in the presence or not (control) of 10⁻⁴  m to 10⁻⁶  m (±)‐catechins (in 0.02% (v/v) acetone). Means are values ± SD (n = 25). For each date, means are not significantly different from the control (Tukey‐test, P < 0.05).

Figure 4

(±)‐Catechins inhibit cytokinin‐mediated prehaustorium formation in Phelipanche ramosa. Germinated seeds were treated with c/tZ (10⁻⁸  m) as haustorium‐inducing factor in the presence or not of (±)‐catechins 10⁻⁴  m to 10⁻¹⁰  m (in 0.02% (v/v) acetone). Positive (C+) and negative (C−) controls consisted in treatments with 10⁻⁸  m c/tZ (in 0.02% acetone) and 0.02% (v/v) acetone (solvent) alone, respectively. Means are values ± SD (n = 15). Means annotated with asterisks are significantly different from the control (Tukey‐test, ***P < 0.001).

Figure 5

(±)‐Catechins inhibit Phelipanche ramosa attachment to Solanum lycopersicum roots and promote parasite tubercle necrosis. Tomato plants infested by P. ramosa were supplied with 50 mL of 0.02% acetone (Control, − catechins) or 50 mL of 10⁻⁵  m (±)‐catechins in 0.02% acetone (+ catechins) at 14 DPI, 28 DPI and 35 DPI. (A) Parasite attachments were counted at 63 DPI. Means are values ± SD (n = 15 plants). Means annotated with asterisks are significantly different from the control (Tukey‐test, *P < 0.05 and **P < 0.01). (B) Pictures of viable and necrotic tubercles were taken at 63 DPI. White arrows: viable tubercles harvested from plants supplied with 0.02% acetone; yellow arrows: necrotic tubercles harvested from plants supplied with 10⁻⁵  m (±)‐catechins, respectively.