Expression of chalcone synthase gene in ginger (Zingiber officinale Rosc.) as influvenced by various management practices

Abstract

Ginger (Zingiber officinale Rosc.), a rhizomatous spice crop is known for its nutraceutical potential due to the presence of non-volatile pungent principles, gingerols. The pungent principles in ginger are derived via “stilbenoid, diarylheptanoid and gingerol biosynthesis” pathway and the key enzyme involved in gingerol biosynthesis is Chalcone synthase. The present research work was undertaken at Centre for Plant Biotechnology and Molecular Biology (CPBMB), College of Horticulture, Kerala Agricultural University, Thrissur from 2017 to 2019 to analyse the influence of nutrient management and spraying of elicitors on Chalcone synthase gene expression in ginger. The study was conducted under two situations, in high tech polyhouse available at CPBMB and in open conditions. Various treatments viz., T1 (Nutrient management as per PoP, KAU), T2 (PoP soil test based nutrient management), T3 (Adhoc PoP organic, KAU), T4 (PoP nutrient management, KAU + salicylic acid foliar spray - 100 µM) and T5 (PoP nutrient management, KAU + methyl jasmonate foliar spray, 100 µM) were imposed. The KAU released ginger variety Karthika, known for its high gingerol content was used for the experiment. The morphological observations such as length of pseudostem, number of tillers per plant, number of leaves per tiller and leaf area were recorded at 60, 90 and 120 Days After Planting (DAP). All the treatments except T4 (PoP nutrient management KAU + salicylic acid foliar spray, 100 µM) and T5 (PoP nutrient management, KAU + methyl jasmonate foliar spray, 100 µM) recorded higher pseudostem length irrespective of the growing conditions. The plants under polyhouse recorded higher pseudostem length than the plants raised under open condition. The tiller production was higher in plants grown in open condition. The number of leaves per tiller was less in treatment T5 (PoP nutrient management, KAU + methyl jasmonate foliar spray - 100 µM) both under polyhouse and open conditions. In polyhouse condition, the leaf area was higher than in open condition.

The relative expression of Chalcone synthase gene was studied from the leaves of various treatments at 120 DAP. All the treatments in polyhouse and open conditions recorded higher gene expression over the control treatment T1 (Nutrient management as per PoP, KAU). The treatment T2 (PoP soil test based nutrient management) recorded the highest expression of Chalcone synthase gene both under polyhouse and open conditions with a fold increase of 1.346 and 1.166 respectively. The plants under polyhouse recorded higher fresh yield of the rhizomes than plants under open condition. The treatment T1 (Nutrient management as per PoP, KAU) was the best irrespective of the growing conditions with regard to fresh yield. The rhizome characters such as number, length and girth of primary, secondary, tertiary fingers, thickness of inner core, colour and plumpiness of rhizomes were recorded. Rhizome characters were good in the treatments T1 (Nutrient management as per PoP, KAU), T2 (PoP soil test based nutrient management) and T3 (Adhoc PoP organic-KAU). There was no significant difference in the dry ginger recovery for the rhizomes harvested from both polyhouse and open conditions. The treatment T2 (PoP soil test based nutrient management) recorded higher recovery of both oleoresin and gingerol. The increased recovery of oleoresin in the treatment T2 (PoP soil test based nutrient management) was 71.16 per cent over the control in open condition and 32.11 per cent in polyhouse over the control. Similarly, the total gingerol content recorded an increase of 15.28 per cent over the control in polyhouse and 31.98 per cent over the control in open condition. The major outcome of the present investigations is the high recovery of total gingerol in soil test based nutrient management in ginger. The abiotic elicitors like salicylic acid and methyl jasmonate sprayed could not improve the recovery of gingerols. The soil test based nutrient management recorded higher recovery of both oleoresin and gingerol and was found cost-effective when compared to the other treatments.