Differences in ABA synthesis and oxidase stress between quinclorac-resistant and -sensitive Echinochloa crus-galli var. zelayensis

Abstract

Quinclorac resistance in barnyardgrass has attracted more and more attention. Quinclorac rapidly affecting the expression of photosynthesis-related genes in quinclorac-sensitive Echinochloa crus-galli var. zelayensis was confirmed in our previous study. In this article, the mRNA level of 9-cis-epoxycarotenoid dioxygenase gene, a key gene in abscisic acid (ABA) biosynthesis, was found to increase to 7.9–11.7 times of control by quinclorac in sensitive and resistant biotypes. But the ABA content was only induced to rise in sensitive biotype, more than 40 times. It was also found that malondialdehyde content in sensitive biotype was 2.1 and 2.2 times that of two resistant biotypes after quinclorac treatment. But evaluation of antioxidant enzyme activity and mRNA levels of antioxidant genes indicated that the number of antioxidant enzymes and increase in mRNA levels of antioxidant genes induced by quinclorac in resistant biotypes were both less than those in sensitive biotype. The present study revealed a new mechanism of quinclorac resistance. Resistant biotypes were induced by quinclorac to produce less ABA, suffered less oxidative damage, and thus avoided the damage by quinclorac. Supplemental data for this article is available online at http://dx.doi.org/10.1080/09670874.2021.2024618