Multipronged Phenotyping Approaches to Characterize Sugarcane Root Systems

Summary

Characterizing root system traits is one of the areas of research that is still in its infancy, particularly in sugarcane. Integrating multiple approaches to precisely phenotype sugarcane roots leads to comprehensive and holistic results, enabling the utilization of identified traits and mechanisms for conventional and molecular breeding.

Abstract

Roots are the primary conductors of water and nutrients and play a vital role in sustaining growth and yield under stressful environments. The study of plant roots poses methodological difficulties in in situ assessment and sampling, which is especially true for sugarcane (Saccharum spp.). Traditional methods during the 1920s documented the genotypic variation in sugarcane root systems, after which few studies were reported on sugarcane root traits per se until recently. In addition to morphology, rhizosphere characteristics, including allelopathic effects and/or affinity for microbial symbiosis, determine plant establishment and survival.

Ultimately, root systems define the above-ground productivity of sugarcane. With the impetus for climate-resilient varieties, it is becoming more relevant to explore and utilize the variability in root system traits of sugarcane. This paper describes multipronged approaches for sugarcane root phenotyping, including field excavation by trench sampling, the use of a root core sampler, raised platforms for root sampling, and raising plants under hydroponic culture, employed by a team of scientists at the Indian Council of Agricultural Research-Sugarcane Breeding Institute (ICAR-SBI).

Field excavation by trench sampling is imperative to assess the plant roots in their natural growing environment. The use of raised platforms simulating field conditions and a root core sampler are alternative approaches, with a considerable reduction in time, uniform sample size, and less loss of root material. Hydroponic plant culture allows the study of morphology, anatomical features, and rhizosphere biology, including the exudation of organic compounds and microbial interactions. Data generated from different experiments using diverse sampling methods add to the wealth of information on the root system traits of sugarcane.

Introduction

Sugarcane (Saccharum spp.), an important food and bioenergy source, is a significant industrial crop suited for cultivation in many countries with tropical and subtropical climatic conditions. Owing to the C₄ photosynthetic pathway for carbon assimilation, sugarcane is highly productive, efficiently using farm inputs such as water and fertilizers. Post-harvest processing of sugarcane yields economically valuable products such as sugar and jaggery, alongside its byproducts-molasses, ethanol, and energy. Sugarcane is produced by nearly 100 countries over an area of 25.97 Mha, which is approximately 1.5% of total arable land. India alone contributes t....

Protocol

1. Field excavation by trench sampling

1. Raise commercial sugarcane hybrids (hereafter called "varieties") in the field from two-budded setts planted at a row spacing of 120 cm, with 90 cm within rows, following the recommended package of practices (POP) to ensure good crop establishment and growth.
2. At the end of the maturity phase of the crop, employ an excavator to dig a trench (1.5 m deep and 1.0 m wide) in the field. Through continuous water jetting, ensure that the soils from root zones are cleared without damaging the roots (Figure 1).
3. When the adhering soil loosens, uproot the cane alo....

Results

Variation in the root morphological traits of sugarcane varieties
Representative images of the root system in Co 62175, excavated from the field by trench sampling and grown in a hydroponic setup, are presented in Figure 5A,B. Long roots (~100 cm) were observed in the varieties Co 62175 and Co 99006, while Co 99006 recorded the highest root weight (127 g·clump⁻¹). Root traits were recorded using a root core sampler, which revealed that Co 6217.......

Discussion

Root systems define the above-ground productivity of sugarcane, necessitating that all its facets be explored and understood thoroughly for the development of climate-resilient varieties. A team of scientists at ICAR-SBI comprising plant physiologists, a microbiologist, an agricultural engineer, a biochemist, and plant breeders employed multipronged approaches for sugarcane root phenotyping, including field excavation by trench sampling, the use of a root core sampler, raised platforms for root sampling, and raising plan.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Aeration pump with pipeline accessories	Purchased from local sources	NA	Used for hydroponic culture of sugarcane
Boric acid	Sisco Research Laboratories, India	80266	Preparation of modified Hoagland's solution
Calcium nitrate	Central Drug House, India	27606	Preparation of modified Hoagland's solution
Composted coir pith	Purchased from local sources	NA	Used for germinating sugarcane setts
Cupric sulphate	Sisco Research Laboratories, India	38869	Preparation of modified Hoagland's solution
DEAE-cellulose	Sisco Research Laboratories, India	10529	anion exchange resin for processing of root exudates
EDTA-ferric monosodium salt	Sisco Research Laboratories, India	59389	Preparation of modified Hoagland's solution
Farm yard manure	Purchased from local sources	NA	Used for germinating sugarcane setts
Glass tanks	Fabricated in-house	NA	Used for hydroponic culture of sugarcane
HPLC	Agilent Technologies	1200 Infinity	Quantification of organic acids in root exudates
Magnesium sulphate	Sisco Research Laboratories, India	29117	Preparation of modified Hoagland's solution
Manganese chloride	Sisco Research Laboratories, India	75113	Preparation of modified Hoagland's solution
Molybdic acid	Sisco Research Laboratories, India	49664	Preparation of modified Hoagland's solution
Potassium dihydrogen phosphate	Central Drug House, India	29608	Preparation of modified Hoagland's solution
Potassium nitrate	Central Drug House, India	29638	Preparation of modified Hoagland's solution
Protrays	Fabricated in-house	NA	Used for germinating sugarcane setts
Red soil	Purchased from local sources	NA	Used for germinating sugarcane setts
Root core sampler	Fabricated in-house	NA	Used for in situ root sampling
Sand	Purchased from local sources	NA	Used for germinating sugarcane setts
Seralite-120	Sisco Research Laboratories, India	14891	cation exchange resin for processing of root exudates
Supporting frame	Purchased from local sources	NA	Used for hydroponic culture of sugarcane
Water motor pump	Purchased from local sources	NA	Used for hydroponic culture of sugarcane
Whatman filter paper grade 1	Universal Scientific	1001090	Processing of root exudates
WinRhizo PRO (software)	Regent Instruments Inc., Canada	STD4800	Two-dimensional root scanner with software for analysis of roots
Zinc sulphate	Sisco Research Laboratories, India	76455	Preparation of modified Hoagland's solution