Collection and evaluation of kasthuri manjal (Curcuma aromatica salisb)

Abstract

Curcuma aromatica Salisb. commonly known as kasthuri manjal is a member of the genus Curcuma belonging to the family Zingiberaceae. Rhizomes of C. aromatica are considered antibacterial and antifungal and are also renowned for their cosmetic use. Despite diverse applications and good export potential, cultivation of kasthuri manjal has not become widespread, mainly because of ignorance about the true identity of the crop. This also makes it easy for the vendors to sell any commonly available curcuma species, especially C. zedoaria (Manjakoova), at an enhanced price as kasthuri manjal. Increased demand coupled with the high rate of substitution demands urgent measures for the popularization of the cultivation of kasthuri manjal. The present study was undertaken at the Agronomy farm, Department of Agronomy, College of Agriculture, Vellanikkara, Thrissur, Kerala from May 2020 to December 2021. The objectives of the study included the collection, characterization and evaluation of C. aromatica accessions in terms of morphological, biochemical, physiological, molecular and yield characters and the assessment of the influence of spacing and propagule size on growth, yield and quality of kasthuri manjal. Thirty three C. aromatica accessions were collected from different parts of Kerala from January to February 2020. These accessions were evaluated in the field for their morphological, biochemical, physiological and yield characteristics. High degree of variation was observed among accessions. All the accessions had open pseudostem habit, distant leaf venation pattern, wavy leaf margin, erect leaf disposition, intermediate number of leaves on the main tiller and close internode pattern of the rhizome. Fourteen attributes (leaf colour on dorsal side, leaf colour on ventral side, pseudostem colour and anthocyanin colouration of pseudostem, rhizome habit, rhizome shape, rhizome length, status of tertiary rhizome, rhizome inner core colour, plant height, number of tillers, leaf lamina length, leaf lamina width, petiole length and crop duration) were dimorphic. Rhizome length, number of mother rhizomes and dry recovery were polymorphic. Acc.2, Acc.22, and Acc.23 had curved rhizomes and Acc.16 produced tertiary rhizomes. These morphological characters can be considered as an identification marker for these accessions. Cluster analysis was done to classify the accessions using morphological characters, and two clusters were obtained at 0.5 dissimilarity coefficient. The first principal component accounted for 55.13 per cent of total variance, and the important contributing traits were shoot biomass yield, leaf area, number of fingers, plant height and rhizome yield. High phenotypic coefficient of variation and genotypic coefficient of variation was exhibited by seven characters; number of tillers, number of leaves, rhizome spread, number of fingers, shoot biomass yield, dry matter accumulation and rhizome yield. Rhizome yield, rhizome spread, shoot biomass yield and leaf area showed highest heritability. Rhizome yield (g/plant) had showed a strong positive correlation with plant height, number of tillers, number of leaves, leaf area, shoot biomass yield, number of fingers and dry matter accumulation. Path analysis was done with characters that showed positive correlation with rhizome yield. High positive direct effect on rhizome yield was expressed by dry matter accumulation and number of fingers. These characters (number of fingers and dry matter accumulation) which showed positive and high direct effect on rhizome yield along with rhizome yield were taken as criteria for scoring and ranking of accessions. Acc.24 ranked first with respect to rhizome yield followed by Acc.19, Acc.17, Acc.3, Acc.7 and Acc.6. Acc.30 recorded the lowest rhizome yield, yield parameters and growth parameters. Based on biochemical characteristics (chlorophyll, crude fibre and volatile oil), 33 accessions were placed into two clusters. The first principal component accounted for for 34.57 per cent of the total variation and the contributing traits were chlorophyll content and crude fibre content whereas, volatile oil had negative effect on PC1. Molecular characterization of C. aromatica accessions done using 34 ISSR primers. Twenty-five primers yielded distinct, easily detectable bands of variable intensities. Maximum per cent polymorphism was obtained (100%) with 22 ISSR primers while the lowest polymorphism was observed with primer ISSR 4 (48.96%). The maximum scorable bands (265) were generated by primer SPS 1 and 232 of them were polymorphic, whereas primer ISSR 814 generated only 39 polymorphic scorable bands. C. aromatica accessions revealed a significant level of polymorphism (95.67%). DNA fingerprints were developed for six accessions having higher yields (Acc.3, Acc.6, Acc.7, Acc.17, Acc.19 and Acc.24). The primers ISSR 5, HB 13, ISSR 7 and SPS 5 produced a maximum of 7 distinct fingerprints. In contrast, ISSR 825 and SPS 1 did not produce such amplicons. Cluster analysis was done to classify the accessions using ISSR amplification data, two clusters were obtained at 0.2 dissimilarity coefficient. Experiment to standardize the spacing and propagule size of C. aromatica. was laid out with a two-factor completely randomized block design with three replications under open and shaded conditions. Spacing 60 cm x 40 cm had significantly higher yield parameters, followed by 40 cm x 25 cm and 25 cm x 25cm under open and shaded conditions. However, due to the increased plant population under closer spacing, the rhizome yield (kg/ha) and dry rhizome yield (kg/ha) were higher in closer spacing. Compared to smaller (5 g) propagules, bigger propagules (10g and 20 g) gave better per-plant yield and yield parameters. Volatile oil was higher for 60 cm x 40 cm spacing and for 20 g propagules under shaded condition. Growing of Curcuma aromatica using 10-20 g seed rhizomes with a spacing of 25 cm x 25 cm is better for getting higher rhizome yield.