Field and Molecular Evidence for Tolprocarb-Induced Phytoalexin Production and Weed Suppression in Rice

Keisuke Tomita, Kakeru Toribe, Hiroyuki Hagiwara, Takuya Ando, Kosuke Yoshino, Mikio Tsuda, Hideaki Nojiri and Kazunori Okada ()
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Keisuke Tomita: Agro-Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
Kakeru Toribe: Agro-Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
Hiroyuki Hagiwara: Mitsui Chemicals Crop & Life Solutions, Inc., 1-19-1 Nihonbashi, Chuo-ku, Tokyo 103-0027, Japan
Takuya Ando: Mitsui Chemicals Crop & Life Solutions, Inc., Agrochemicals Research Center, 1358 Ichimiyake, Yasu-shi, Shiga 520-2362, Japan
Kosuke Yoshino: Mitsui Chemicals Crop & Life Solutions, Inc., Agrochemicals Research Center, 1358 Ichimiyake, Yasu-shi, Shiga 520-2362, Japan
Mikio Tsuda: Mitsui Chemicals Crop & Life Solutions, Inc., 1-19-1 Nihonbashi, Chuo-ku, Tokyo 103-0027, Japan
Hideaki Nojiri: Agro-Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
Kazunori Okada: Agro-Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan

Agriculture, 2025, vol. 15, issue 19, 1-15

Abstract: Tolprocarb (TPC), a fungicide primarily used for controlling rice blast, was recently shown to stimulate disease resistance in rice. To elucidate the molecular basis of this immunostimulatory effect, we conducted transcriptomic, metabolic, and field-based analyses focusing on diterpenoid phytoalexins, key antimicrobial and allelopathic compounds in rice. Microarray analysis revealed that TPC treatment induced a broad transcriptional activation of genes involved in phytoalexin biosynthesis, including DPF , a master regulator of diterpenoid metabolism. Consistent with this, LC-MS/MS analyses confirmed the accumulation of momilactones A and B, as well as phytocassanes B, C, and E, in rice leaves after TPC application, a response not observed with conventional resistance inducers such as probenazole or carpropamid. In root tissues under controlled conditions, phytoalexin accumulation was limited, and exudation into the rhizosphere was minimal. However, field experiments showed that TPC treatment led to a transient increase in leaf momilactones around 14 days post-transplanting, followed by increased exudation into the rhizosphere at 21 days. Notably, this increase in root exudation coincided with a reduction in total weed biomass, although weed species composition remained unchanged. These findings suggest that TPC not only enhances rice immunity through phytoalexin induction but may also contribute to weed suppression via allelopathic root exudates in field settings. Our study highlights a dual role for TPC in rice cultivation, boosting disease resistance and suppressing weed growth, and underscores the potential of phytoalexin-focused strategies for integrated crop protection.

Keywords: rice; disease resistance; fungicide; phytoalexins; weeds; exudate; allelopathy (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2025
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