Irrigation timing as a glucosinolate alteration factor in radish (Raphanus sativus L.) (Gya Labuk and Tsentay Labuk) in the Indian Trans-Himalayan region of Ladakh

Abstract

Radish (Raphanus sativus L.) is a root vegetable with Glucosinolates (GSLs), which is a secondary metabolite that has conducive to human health and promotes anti-inflammatory and anticancer activities in cells. We conducted a study to determine if irrigation timing has an impact on the GSL properties and pungency of two radish cultivars from Ladakh, which are locally called Gya Labuk and Tsentay Labuk. The four irrigation timing as the morning (6.00 AM), noon (12.00 P M), and evening (4.00 PM) and control (anytime) irrigated twice a week. The GSL profile of roots and leaves was done using High Pressure Liquid Chromatography (HPLC). Through this process, we identified nine GSL compounds in root and leaf of radish, which included five that were aliphatic and four that were indole glucosinolate compounds. The most abundant GSL in radish root and leaf was Glucoraphasatin (GRH), which accounts for 89.38–89.51 % and 74.85–88.58 %of the total GSL in the two cultivars grown in Ladakh i.e. Gya Labuk and Tsentay Labuk respectively. The total GSL ranged from 120.12 ± 4.89–225.22 ± 79.77 μmol g-1 in Gya Labuk root and 121.17 ± 6.79–296.68 ± 23.53 μmol g-1 in Tsentay Labuk root. The GRH value ranged from 46.43 ± 13.52–174.94 ± 8.71 μmol g-1 in the leaves of Gya Labuk and ranged from 64.82 ± 5.70–149.12 ± 7.09 μmol g-1 in the leaves of Tsentay Labuk. In our investigation, we found that noon irrigated radish had higher total GSL content in both root and leaves as compared to ones irrigated at other times. We also found that dark coloured radish (Gya Labuk) root had a lower concentration of GSL than light coloured ones (Tsentay Labuk). The highest GSL was observed in Tsentay Labuk with light coloured roots while the low GSL was in Gya Labuk with dark pink coloured root.