Regulation of curcuminoids, photosynthetic abilities, total soluble sugar, and rhizome yield traits in two cultivars of turmeric (Curcuma longa) using exogenous foliar paclobutrazol

Daonapa Chungloo,Rujira Tisarum,Thapanee Samphumphuang,Suriyan Cha-Um,Thanyaporn Sotesaritkul

doi:10.15835/nbha49312445

Abstract

Paclobutrazol (PBZ) is a member of plant growth retardants, commonly applied for growth regulation, yield improvement, and biotic and abiotic stress alleviation. However, the effects of PBZ on turmeric (Curcuma longa L.; Zingiberaceae), a rhizomatous herb, have not been well established. The objective of this investigation was to gain a better understanding of the effect of PBZ on two different varieties of turmeric plants, ‘Surat Thani’ (‘URT’; high curcuminoids >5% w/w) and ‘Pichit’ (‘PJT’; low curcuminoids <3% w/w). Pseudostem height of cv. ‘PJT’ treated by 340 µM PBZ was significantly decreased by 14.82% over control, whereas it was unchanged in cv. ‘URT’. Interestingly, leaf greenness (SPAD value), maximum quantum yield of PSII (Fv/Fm) and photon yield of PSII (ΦPSII) in cv. ‘PJT’ treated by 340 µM PBZ were significantly elevated by 1.47, 1.28 and 1.23 folds, over control respectively. Net photosynthetic rate (Pn) in cv. ‘PJT’ declined by 38.58% (340 µM PBZ) over control, as a result of low levels of total soluble sugars (TSS; 127.8 mg g-1 DW) in turmeric rhizome. A positive relation between photosynthetic abilities and aerial fresh weight was demonstrated. In addition, a negative relationship between TSS and total curcuminoids was evidently found (R2 = 0.4524). Curcuminoids yield in turmeric rhizomes significantly dropped, depending on the degree of exogenous foliar PBZ applications. In summary, cv. PJT was found to be very sensitive to PBZ application, whereas rhizome yield and growth traits and high amount of curcuminoids were retained in cv. ‘URT’. Plant growth retention in turmeric cv. ‘URT’ using 170 mM PBZ foliar spray without negative effects on rhizome biomass and total curcuminoids content was demonstrated.

Highlights

Turmeric (Curcuma longa L.; Zingeberaceae) is a rhizomatous herb, which has been widely cultivated as a spice in tropical regions, especially in India (Akram et al, 2010)
Overall growth performance, leaf greenness (SPAD), chlorophyll fluorescence, net photosynthetic rate, and soluble sugars were measured in the leaf tissues as well as total curcuminoids and total soluble sugars in rhizomes were assayed
‘Chiang Mai Pink’), pseudostem height of 1,500 mg L−1 PBZ-treated plants were retarded by 50% of control and slow growth rate was observed when compared with control plants (Jungklang et al, 2017)

Summary

Introduction

Turmeric (Curcuma longa L.; Zingeberaceae) is a rhizomatous herb, which has been widely cultivated as a spice in tropical regions, especially in India (Akram et al, 2010). Turmeric plant contains curcuminoids and has been used as food ingredient, edible dye and traditional medicine (Sharma et al, 2005; Anandaraj and Sudharshan, 2011). An increasing demand of turmeric varieties for the food, pharmaceutical, and cosmetic industries has been reported due to its medicinal properties. A novel cultivation system to yield high curcuminoids and high biomass of rhizomes in turmeric plant still needed to be discovered (Deepa et al, 2017; Sandeep et al, 2017). In India, high yielding turmeric cultivars (HYTCs), namely ‘Palam Pitamber’ (32.94 t ha−1) and ‘Palam Lalima’ (32.35 t ha−1) are cultivated as elite varieties, with high rhizome productivity, profitability, and curcuminoids yield (Choudhary and Rahi, 2018). PJT have been selected from the turmeric plant characterization to play as negative check

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Discussion

Conclusion