**1. Introduction**

Low temperature is a significant abiotic factor in China limiting plant dispersion on land, impeding plant growth and crop productivity, yield, and quality, and limiting the geographical area suited for cultivating a specific plant species [1–3]. Crops are exposed to periods of intense cold in many parts of the world [4], and tropical plants are more susceptible to chilling than plants growing in cold climates [5].

Jute is an annual herb in the Malvaceae family, with two commercial species, *C. capsularis* and *C. olitorious* [6]. Jute is produced in twenty countries, although Bangladesh, India, and China account for 85% of global production [7,8]. Jute fiber is naturally occurring, soft,

**Citation:** Dey, S.; Biswas, A.; Huang, S.; Li, D.; Liu, L.; Deng, Y.; Xiao, A.; Birhanie, Z.M.; Zhang, J.; Li, J.; et al. Low Temperature Effect on Different Varieties of *Corchorus capsularis* and *Corchorus olitorius* at Seedling Stage. *Agronomy* **2021**, *11*, 2547. https:// doi.org/10.3390/agronomy11122547

Academic Editors: Channapatna S. Prakash, Ali Raza, Xiling Zou and Daojie Wang

Received: 11 November 2021 Accepted: 13 December 2021 Published: 15 December 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

shiny, longest, strongest, and most recyclable derived from stem bark [8]. Recently, jute has gained popularity as herbal medicine, renewable biofuel, and paper fiber [8–10]. Thus, the global demand for jute is increasing [11]. As global environmental awareness rises, more people are actively purchasing environmentally friendly products. While jute is a natural fiber, they have many composite-like properties like rigidity and flexibility. Jute would be a unique source to supply the global demand for eco-friendly fibers.

It provides luxuriant growth in a warm and humid climate with temperatures between 24 ◦C and 37 ◦C for optimum fiber yield, and the growth rate gradually slows down when temperatures fall below this range [12]. It has been reported that jute is a short-day fiber plant. The majority of biological responses that occur in jute are temperature dependent. Any early planting provides premature flowering and reduces plant growth and yield of fiber due to thermal sensitivity. It was reported that some varieties can be planted early with the absence of premature flowering in appropriate sowing time [12]. In China's subtropics, where cold weather is unpredictable, extending the growing season (early planting and late harvesting) is crucial. Intensive cropping during late March and early April could make jute more profitable in China's subtropics and warm temperate zones, as well as in jute growing countries. It was proved that appropriate sowing and harvesting could allow facilities to fit the crop in three cropped patterns [12]. If an intensive cropping pattern could be established in which jute is produced from late February to early March, it is believed that jute could be more profitably cultivated in Asia's jute producing countries [13]. For this purpose, new varieties that are tolerant to low temperatures will be required; therefore, new varieties should be developed to endure various biotic and abiotic stresses.

However, there is no proof of physiological or biochemical investigation for jute's cold tolerance mechanism. In a previous study carried out only on the molecular level, where DNA fingerprinting randomly amplified polymorphic DNA (RAPD) and automated amplified fragment length, polymorphism (AFLP) was used to detect or distinguish between cold-tolerant and cold-sensitive jute species was assessed [13]. Findings indicated that eight primer combinations distinguished the two cold-sensitive and four cold-tolerant jute populations using 93 polymorphic fragments. Understanding low-temperature adaptation is crucial to developing cold-tolerant crops. It has been reported that extreme temperature can cause changes in numerous physiological, biochemical, molecular, and metabolic processes, including membrane fluidity, enzyme activity, and homeostatic metabolism, which can impact agriculture [14] by overproducing reactive oxygen species (ROS), such as superoxide anions (O2 −) and hydrogen peroxide (H2O2). Interestingly, plants have antioxidant systems with various enzymatic and non-enzymatic components to protect them from the injury caused by reactive oxygen species ROS [15]. Plants have evolved many antioxidant systems and osmolytes to cope with stress. These include superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), glutathione (GSH), and proline, all of which contribute to scavenging H2O2 with different mechanisms under stressful conditions and avoid oxidative damage [16–18]. Understanding low-temperature adaption processes are crucial for the development of cold-tolerant crops. This research report summarizes the physiological responses of a representative sample of jute varieties to cold stress, as ascertained by quantification of photosynthetic parameters, ROS-mediated damage, antioxidant accumulation, and osmolyte accumulation, all of which differentiate the sensitive and tolerance jute phenomes. The main purpose of the present study was to evaluate low temperature physiological, biochemical, and antioxidant defense responses to verify the tolerance level of seven selected *C. capsularis* and *C. olitorius* varieties from earlier experiments.
