Propagation studies in Rue (Ruta graveolens L.)

Abstract

Ruta graveolens L., commonly rue plant belongs to Rutaceae family. This greyish-green-coloured shrub has a sharp, unpleasant odour and grows to a height of about one metre. Originating from the arootha areas of the Idukki and Wayanad districts of Kerala. Local people in these areas are using it to cure many diseases. Around the globe, it is used in conventional medical systems to cure ailments such as rheumatic pain, varicose veins, and skin disorders such as psoriasis and dermatitis. The extracts from rue have been used to cure snake and scorpion venom. Some contemporary findings show that rue has a selective inhibitory action on gram (+) bacteria such as Staphylococcus aureus, Streptococcus pyogenes, Listeria monocytogenes and Bacillus subtilis. The primary component, Rutin, present in it has potential to generate neuroprotective effects. However, the utilization of rue to its potential has a major constraint, i.e., the availability of planting material. Currently, no standard procedure for the propagation of rue is followed. Propagation studies in Rue (Ruta graveolens L.) formulated and carried out in the Department of Plantation Spices Medicinal and Aromatic Crops during 2022-23, which comprised three experiments viz., Standardization of suitable vegetative propagation methods in Standardization of rooting medium for the propagation of propagation method using stem cuttings and Plant Growth Regulator treatment, and suitable rooting media. Apart from the vegetative propagation, the morphological characterization of rue accessions was done along with the quantitative estimation of Rutin content using HPTLC technique as the third experiment. The first experiment evaluated vegetative propagation using two types of cuttings (terminal and semi-hardwood cutting) and eight different PGR concentrations including control (distilled water), IBA, NAA, combinations of IBA and NAA together and Keradix (commercial rooting powder). The single effects of type of cutting, PGR concentrations used and their interaction effects on the shoot, root and general parameters were studied up to 120 days after planting (DAP). Regarding the single effect of type of cuttings, the minimum number of days taken for sprouting was in semi-hardwood cuttings (16.40). Terminal cuttings showed the highest sprouting percentage of 90.37 percentage. The highest number of new sprouts, leaves, adventitious roots and primary branch of roots were found in terminal cuttings (3.22, 3.12, 26.67, 261.85, respectively) at 120 DAP. The shoot and root length were also high in terminal cuttings (25.60 cm and 13.85 cm at 120 DAP). The fresh and dry weight of shoots, roots and total biomass production was also higher in terminal cuttings (20.85, 2.93, 2.91, 1.04 and 3.98 g, respectively) at 120 DAP. Terminal cuttings gave the highest rooting percentage of 51.85, a root volume of 2.88 cm3, and the highest root-to-shoot ratio of 0.38. The terminal cuttings had the highest survival of 51.85 percentage. The effects of PGR concentrations showed that Indole-3-Butyric Acid (IBA) 250 ppm showed the lowest number of days to sprout (14.33). The combination of IBA 250 ppm and NAA 250 ppm gave the highest number of new sprouts, dry weight, rooting percentage, number of adventitious roots, number of primary branch of roots, fresh weight of roots, dry weight of roots, total biomass production and survival percentage (4.00, 3.66 g, 58.33%, 29.00, 255.17, 3.21 g, 1.11 g, 4.77 g and 58.33%, respectively) at 120 DAP. Naphthalene Acetic Acid (NAA) 500 ppm gave the highest sprouting percentage (88.33%) and root volume (3.23 cm3) at 120 DAP. The most extended shoot length was observed in IBA 500 ppm, having 26.10 cm at 120 DAP. IBA 250 ppm recorded the highest number of new leaves (3.41) and fresh shoot weight (21.73 g) at 120 DAP. The root length was highest in NAA 250 ppm (15.82 cm) at 120 DAP. The highest root to shoot ratio (0.43) was observed in IBA 250 ppm at 120 DAP. The interaction of type of cutting with PGR showed that terminal cutting × IBA 250 ppm + NAA 250 ppm (C1T6) with highest sprouting percentage (100%), highest number of sprout (4.67), fresh weight of shoot (26.64 g), rooting percentage (86.67%), number of adventitious roots (33.00), fresh weight of root (3.51 g), dry weight of root (1.16 g) and survival percentage (86.67%) at 120 DAP. Semi-hardwood × control (C2T1) took the least days to sprout (14.00). Terminal × NAA 250 ppm (C1T5) gave the highest shoot length (30.48 cm) and root volume (3.57 cm3). Semi-hardwood × IBA 250 ppm (C1T2) gave the highest number of new leaves (4.31) and fresh weight of shoots (23.86 g) at 120 DAP. The most extended root length was observed in semi hardwood × NAA 250 ppm (C2T4). The second experiment evaluated the rooting media to be standardized for rue propagation. Potting mixture (sand, soil and FYM in 1:1:1 ratio) alone, and treated separately with Trichoderma, AMF and Phosphobacterium were utilized. Besides, coirpith-compost and perlite in the ratio of 3:1 alone, and in combination treated separately with Trichoderma, AMF and Phosphobacterium were also used in this experiment. The potting mixture treated with AMF gave sprouts in fewer days (13.00). Potting mixture treated with Phosphobacterium gave higher number of sprout (1.00), sprouting percentage (88.89), number of leaves (1.67), length of new shoot per cutting (29.46 cm), fresh weight of shoot (26.45 g), dry weight of shoot (3.56 g), percentage of cuttings rooted (84.44), fresh weight of root (4.98 g), total biomass production (5.08 g) and survival percentage (84.44) at 120 DAP. Coirpith-compost and perlite in the ratio (3:1) treated with Trichoderma gave a higher number of adventitious roots (46.33) and a higher number of primary branches of roots (344.17) at 120 DAP. Coirpith-compost and perlite in the ratio (3:1) alone gave the highest root-to-shoot ratio (0.83), dry weight of root (1.81 g) and length of longest root (21.58 cm) at 120 DAP. The third experiment studied the morphological variations present within four rue accessions maintained in the Department of Plantation Spices Medicinal and Aromatic Crops, and the accessions were named RG 1, RG 2, RG 3 and RG 4 based on the location of the collection. There was variability among stem and leaf characters along with slight variation in the leaf colour. The HPTLC analysis showed variability in Rutin present in the accessions. The highest percentage of Rutin was found in RG 4 with 0.56% of Rutin, followed by RG 2 having 0.43% of Rutin, RG 3 having 0.28% of Rutin and RG 1 having 0.24% of Rutin. Terminal cutting treated with IBA 250 ppm + NAA 250 ppm was the best method of vegetative propagation in rue, owing to its high survival percentage, higher biomass production and higher percentage of cuttings rooted. The media consisting of potting mixture treated with Phosphobacterium was the better medium for rooting since it gave a higher survival percentage, higher percentage of rooted cuttings and total biomass production. Hence, the ideal propagation method for rue was found to be terminal cuttings treated with a combination of IBA 250 ppm + NAA 250 and planted in media consisting of potting mixture treated with Phosphobacterium. In the evaluation of four accessions for morphological parameters and Rutin content, it was found that the accession RG 4 was best performing with respect to higher rutin content (0.58 %), erect plant growth habit and dense foliage. However, further studies on evaluation of genotypes having large population is require.