Comprehensive Evaluation for Cold Tolerance in Wucai (Brassica campestris L.) by the Performance Index on an Absorption Basis (PIabs)

Yun Dai,Chenggang Wang,Lingyun Yuan,Rifei Sun,Shujiang Zhang,Jie Wang,Guohu Chen,Mengru Zhao,Shilei Xie

doi:10.3390/agronomy9020061

Abstract

Wucai is a biannual leafy vegetable that is more sensitive to cold than most Brassicaceae vegetables. Here, phenotypic differences in wucai were investigated to identify those genotypes with high cold tolerance at low temperature, which could allow their cultivation in cold climates. In all, on the basis of PIabs, 20 wucai genotypes (10 lower PIabs and 10 higher PIabs) were selected from a collection of 124 genotypes. Both W16-13 and SW-3 (higher PIabs) and the LS-6 and W15-16 (lower PIabs) were screened from the 20 wucai genotypes according to several key plant physiological traits: net photosynthetic rate, electrolyte leakage, chilling injury index, specific leaf area, malondialdehyde contents, and PIabs. To further verify the reliability of PIabs, four genotypes were grown under low temperature gradient conditions and their morphological indexes, chlorophyll content, total antioxidant capacity, fluorescence transients (OJIP transients), leaf cell ultrastructure, and gene expression were measured. These indicators strongly demonstrated that the W16-13 and SW-3, which had higher PIabs, possessed higher resistance to cold stress, while both LS-6 and W15-16 were sensitive to cold. As this study shows, the easily measured performance index, PIabs, could be applied to wucai genotypes to screen for one or more varieties characterized by higher cold tolerance.

Highlights

To determine the relationship between each cold tolerance index and PIabs, the 20 selected genotypes were subjected to an 8-day gradient (25/18 ◦ C d/n to 5/0 ◦ C d/n)
We found that wucai genotypes with a higher of attaining higher photosynthetic efficiency than genotypes with a lower PIabs under cold stress, PIabs were capable of attaining higher photosynthetic efficiency than genotypes with a lower PIabs with a positive correlation between PIabs and Photosynthetic Rate (Pn) confirmed (Figure 3)
We found that high-PIabs (W16-13 and SW-3) had the highest chloroplastic lipocalins (CHL) expression under low temperature, but those of the low-PIabs genotypes (LS-6 and W15-16) and SW-3 had similar Temperature-induced lipocalins (TIL) expression, perhaps because the expression levels of TIL genes were not activated or very weak at low temperature

Summary

Introduction

A cool climate is the best growing environment for wucai, its growth is at risk of cold stress at unusually lower temperatures, which inhibits its normal growth. Genotypes respond differently to cold, with some exhibiting a certain degree of tolerance, while others are extremely sensitive [2]. Finding an efficient and rapid method to reliably distinguish cold tolerance among many genotypes would let us identify those best suited for cultivation in areas that experience cold spells. Another crucial advantage would be the identification of parental material

Methods

Results

Discussion

Conclusion