Phenotyping of Weedy Rice to Assess Root Characteristics Associated with Allelopathy

Brooklyn Schumaker,Te-Ming Tseng,Ziming Yue,Auriana Tucker,Shandrea Stallworth

doi:10.4236/ajps.2021.128084

Abstract

Weedy rice is a species of Oryza, and is a wild relative of cultivated rice. The weed possesses unique hardiness that allows them to thrive in dynamic and stressful environments. These characteristics suggest that weedy rice is a stored source of novel genes for competitive traits. One such trait is allelopathy, where a species releases secondary metabolites that suppress the growth and development of neighboring species. Weed competition is a limiting factor in rice production systems; therefore, it is critical to identify specific allelopathic weedy rice accessions to determine the genetic pathways and mechanisms associated with allelopathy to be used in breeding programs. Due to the complex nature of allelochemical production and the lack of knowledge of allelopathy mechanisms in weedy rice, phenotypic traits, particularly root traits, can be used to overcome this limitation and serve as target characteristics for breeding weed suppressive rice varieties. Five weedy rice accessions were chosen from preliminary screenings of larger sample sizes with the ability to suppress barnyardgrass weed seedling growth. Another five weedy rice with low barnyardgrass suppression was selected for the current root phenotypic study. Five cultivated rice lines were used as a comparison. All plants were propagated in a transparent germination pouch for four weeks. Roots were scanned and analyzed for root length and area covered. No differences were found in the seedling root area among weedy rice and rice accessions; however, allelopathic weedy rice plants exhibited a 14% increase in root length than non-allelopathic weedy rice plants. The allelopathic weedy rice accession B2 possessed the most extended root system (22.4 cm root length). The highly allelopathic weedy rice accessions (including B2) screened and phenotyped in this study are ideal candidates for identifying the genetic controls of early root length, a possible trait contributing to underground allelopathic production and competitive advantage.

Highlights

Plant root structures are notoriously difficult to study
The highly allelopathic weedy rice accessions screened and phenotyped in this study are ideal candidates for identifying the genetic controls of early root length, a possible trait contributing to underground allelopathic production and competitive advantage
Weedy rice displayed a variety of different root lengths and areas

Summary

Introduction

Plant root structures are notoriously difficult to study. Root system architecture (RSA) is defined as the spatial organization of roots and is crucial for normal root functioning. Roots have an innate ability to respond and adapt to external environmental factors, determining the plant’s RSA and giving insight into the soil environment [1]. Phenotyping allelopathic root structures may provide insight into the plant’s ability to thrive and adapt to environmental stresses [2]. Allelopathic interactions involve plants detecting neighbors and adjusting the production and excretion of chemicals as a defensive reaction. Soil depth preference may be one characteristic of root structure architecture contributing to weed suppression [2]. Research efforts to study root structures and how individual aspects relate to plant prosperity are slow, especially in allelopathic phenotypes, because root systems are difficult to observe without damaging the growing plant [1]

Objectives

Methods

Results

Discussion

Conclusion