A significant, lesser-known, unconventional medicinal plant in the Zingiberaceae family is Curcuma caesia, native to Java and Myanmar, is also widely dispersed throughout central and north-eastern India, as well as in Madhya Pradesh, Jharkhand, Chattisgarh, Orissa, and other places of South India (Narendhiran et al., 2023). The rhizomes of the plant Curcuma caesia have a wide range of medicinal properties, including the ability to treat cancer symptoms, diabetes,
high cholesterol, stomach pain, menstrual irregularities, wounds, eczema, and psoriasis
(Arulmozhi et al., 2006). Tribal people use black turmeric plants for tantric sadhana and medicine. Rhizomes are employed by northern tribes as a talisman to ward off evil spirits, while in West Bengal they play a significant role in traditional medicine and are also used as a substitute for turmeric (Mohankumar et al., 2020).The National Medicinal Plant Board (NMPB) of India puts this plant on its list of critically threatened species at the moment. Export restrictions are imposed by the Ministry of the Environment without the consent of the appropriate legal authorities. As a result of high demand, widespread exploitation, and limited cultivation,it has been determined that Curcuma caesia is endangered (Neha et al., 2014).The existence of wide variability among the turmeric genotypes concerning yield attributes and quality characters has been reported by many researchers (Anandaraj et al., 2014; Prasath et al., 2016). Better conservation requires systematic and in-depth genetic characterization. Even in the age of computer technology, morphological characterisation is a useful techniquebecause of its reliability and easy identification with fewer resources for certain stable characters unaltered with environmental interactions. The guidelines of the Protection of Plant Varieties and Farmers Right Act (2009) of India helps in categorizing the morphological characters which are measured quantitatively and qualitatively. Therefore, to characterize a group of 20 Black turmeric genotypes collected from the provenance of the nation, the current investigation was carried out on different morphological and rhizome characters based on DUS guidelines as a measure of conservation of the species.

Materials and Methods:

            Twenty Black turmeric genotypes were collected fromvarious parts of the country (Table 1.) and they were characterized at the Department of Horticulture, Annamalai University, Tamil Nadu. TheCrop was grown during two consecutive seasons of 2020-21 and 2021-22 in a randomized block design with three replications. Rhizomes were planted at a spacing of 30 x 30 cm and all other cultural practices were followed as recommended for Curcuma longa (Jayashree et al., 2015). Five plants of uniform size and vigor were selected for recording observations. Genotypes were evaluated for 16 DUS traits viz., Pseudostem habit, Plant height (cm), Number of leaves, Petiole length (cm), Lamina length (cm), Lamina width (cm), Leaf colour (dorsal side), Leaf color (Ventral side), Leaf margin, Leaf venation pattern, Leaf midrib color, Rhizome habit, Rhizome shape, Number of mother rhizomes, Rhizome inner core colour and Duration (No. of Days). The assessment of characters was done at 150th days after planting for vegetative characters and after harvest for rhizome characters (PPV & FRA, 2009). Observations based on color were recorded under natural light using the Royal Horticultural Society (RHS) Colour chart.

Results and Discussion:

            The genotypes showed considerable variations for the studied characters. Among the sixteen characters studied three were found to be monomorphic viz., Leaf color (ventral), Leaf margin and Number of mother rhizomes. Whereas Pseudostem habit, Plant height (cm), Number of leaves, Leaf color (dorsal), Leaf venation pattern, Rhizome habit, and Rhizome shape showed dimorphic nature. The characters Petiole length (cm), Lamina length (cm),Lamina width (cm), Leaf midrib color, Rhizome inner core color, and Duration were found to be polymorphic.

Morphological characters:

            The pseudostem of BTG3, BTG7, BTG13, and BTG14 showed compact habit, whereas the remaining sixteen genotypes showed open pseudostem habit. None of the genotypes exhibit short stature when considering the plant height. Medium plant height (85-100cm) wasfound in thirteen genotypes while seven genotypes exhibited tall stature (>100cm) which is mostly undesirable. While considering the Number of leaves intermediate type were found more prominent with fourteen genotypes than many type which was found only at six genotypes. The genotypes BTG3, BTG5, and BTG14 exhibited short petiole length (15cm), short lamina length (<30cm), and Narrow Lamina width (10cm) while ten and seven genotypes showed intermediate (15-25cm) and long(>25cm) petiole length respectively. For the character Lamina length nine genotypes exhibited medium length with 30-40cm and eight genotypes were found to be long (>40cm). Broad lamina width was found in five genotypes Viz.,BTG6, BTG11, BTG15, BTG16, and BTG19, while medium lamina width was found in twelve genotypes. Except for BTG3 and BTG5, all were found to have green color in the dorsal side of the leaf whereas BTG3 and BTG5 showed a light green color. The ventral side of the leaf showed a green color in all the genotypes. The leaf margin of all the genotypes exhibited even nature. The unique leaf venation pattern i.e. Distant was found in BTG8, BTG20. The remaining genotypes showed a close leaf venation pattern. The genotypes BTG6, BTG8, BTG20 exhibited grey-purple leaf midrib color while violet-blue and purple were found in five and twelve genotypes respectively. A similar study on turmeric characterization based on DUS character was reported by Deb and Chakrobarty, (2017) and Aarthi et al., 2018.

Rhizome character:

            Except BTG8, BTG17, and BTG19 others showed compact rhizome habit, whereas the above genotypes showed loose rhizome habit. The straight rhizomes were found in BTG8, BTG11, BTG17, and BTG19 while others exhibited curved rhizome shapes. More than three mother rhizomes were found in all the genotypes. The only genotype BTG3 exhibited a greenish blue rhizome inner core color which can be used as a marker for the identification of this genotype. The genotypes BTG5, BTG9, BTG12, and BTG18 exhibited light blue color in their inner core of the rhizome while BTG2, BTG8, and BTG11 showed moderate blue color and the remaining genotypes have strong blue color. Variation in the rhizome core color of turmeric was reported by Mishra et al., 2015; Aarthi et al., 2018.

Duration: –

            The genotypes BTG6, BTG11, BTG15, and BTG19 were found to be earlier (<210days) which is more desirable, while BTG8 and BTG17 showed medium duration(211-240days) and the remaining genotypes showed later maturity. Earliness is a desirable character; early varieties are suitable for areas with serious irrigation problems A similar observation was made in ginger using DUS guidelines to characterize the soma clones (Dev, 2013) and in fifteen turmeric genotypes by Aarthi et al., 2018.

Conclusion: –

            From the study, it was found that the genotypes BTG6,BTG11, BTG12, BTG15, BTG16 and BTG17 had the many leaves, long petiole length, long lamina length, and broad lamina width. These characters were considered as more desirable morphological characters upon which the selection can be made for further development or can be used in the developmental breeding program. Distant leaf venation can be used as a morphological marker for the identification of the genotypes BTG8 and BTG20. More variations were found in the rhizome inner core color character. The greenish-blue rhizome inner core color can be used as the marker identification for the genotype BTG3. The genotypes BTG6,BTG11, BTG15, and BTG19 were found to have early maturity which can be used for commercial production of black turmeric with improved rhizome yield. The variations found in this study emphasize selection based on morphological characters which can be potentially utilized in trait-specific selection.

References: –

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