Evaluation of dragon fruit (hylocereus spp.) genotypes grown in Kerala

Abstract

Dragon fruit (Hylocereus spp.) commonly known as the pitaya, is a perennial climbing vine belonging to the Cactaceae family. The present work carried out in the Department of Fruit Science during the period 2019-2021 to study the morphology, flowering, yield and quality attributes of dragon fruit grown in four districts of Kerala (Thiruvananthapuram, Pathanamthitta, Ernakulam and Thrissur) is of vital importance with respect to the popularity dragon fruit has gained within a very short span of time in Kerala. A total of 100 plants, 10 each from 10 different locations were evaluated based on the UPOV descriptor guidelines to characterise the different genotypes that are being cultivated in Kerala. The plants were denoted as P1 to P10, prefixed with the first two letters of the location to which they belong. The commercial cultivation of dragon fruit in Kerala was found to be dominated by the dark pink/purple fleshed dragon fruit (Hylocereus costaricensis). Within this species, more than one genotype was identified. The stem, flower, yield and quality attributes were found to vary widely. The stem characters included stem segment length (33-210 cm), stem segment width ((1.80-6.60cm), distance between areoles (2.00-5.50 cm), arch height (1.00-4.20 cm), stem waxiness (strong and weak), stem sturdiness (high and low), margin of rib (convex and flat), number of spines per areole (3-5), spine colour (medium brown and dark brown), height of the pole (6.5-8 ft with 1-2 ft buried underground), number of branches (numerous) and number of stem segments per branch (1-6). Variations were also observed for the flower characters such as bud shape (ovate and elliptic), shape of bud apex (acute and rounded), secondary colour pattern of sepal (slightly red edged and red edged), intensity of red colour on bracts (weak, medium and strong), length of style (23.50-31.00 cm) and number of stigma lobes (26-36). The yield characters studied were fruit weight (84-896g), length of fruit (4.60-10.40 cm), width of fruit (4.40-10.40 cm), length/width ratio of fruit (1.00-1.21), number of bracts (18- 50), length of apical bract (3.00-6.30cm), width of base of the bract(1.40-5.70 cm), position of bracts towards the peel (adpressed, slightly held out and strongly held out), fruit weight without peel (52-592 g), fruit shape (oval or spherical), colour of peel 2 (medium pink and dark pink), flesh colour (dark pink and purple) and yield per post (5- 20 kg per year based on the age of the plants). The values ranged from 11 to 18 °B with respect to the TSS of the fruits whereas the titrable acidity was found to be 0.12 per cent in all the fruits. The plants KoP1 to KoP10 from Kozhenchery received the maximum score for appearance, taste, flavour, after taste and overall acceptance. Plants came into bearing within 1.5 to 2 years of planting when stem cuttings were used as the planting material. The duration from flower bud initiation to anthesis was 12-15 days in general and anthesis took place during the night time after 10 p.m. If the pollination was successful, fruit could be visible after 5 to 7 days of anthesis and the harvest was possible in 23-25 days from fruit set i.e., one month after anthesis. When the phenology of the plants was studied, flowering started in the month of March in two locations (Athikkayam and Vaniyampara) whereas in all the other locations, it started in the month of April. The flowering season extended till September to October. The fruiting season started exactly one month after the anthesis and ceased one month after the flowering has stopped, i.e., April to November. As dragon fruit was a perennial crop, different orchards were grouped into three phases based on the age of the plants, namely the establishment phase (0-2 years), yield increasing phase (2-4 years) and yield stabilizing phase (4 years and above). Considering the phases, total cost of cultivation was calculated and it was found to be ₹8,29,393 per year per hectare. The maximum cost during establishment phase was incurred for the planting material and construction of posts. During the maintenance phase, maximum expenditure was for the manure and fertilizer application. Average yield per year per hectare was observed to be around 21 tonnes and the average price received by farmers was ₹174 per kg. Net return from one hectare was around ₹27,32,768. The B:C ratio was 4.29 when the farmers received ₹174 per kg fruit. The B:C ratio obtained with the least price (₹120 per kg) was 3.04. Being a highly remunerative crop, area under dragon fruit cultivation was found to be expanding year after year, as more under-utilized lands are being brought under this crop. Major constraint identified in the cultivation of dragon fruit was the bud and flower drop due to excessive and continuous rainfall during the flowering season. Weed 3 growth was also found to be a major problem. The source of planting material in all the locations under study were found to be either from Malaysia or Cambodia. Since dragon fruit was a crop introduced recently to India, the incidence of pests and diseases were less compared to other fruit crops. But the menace caused by ants was common and rarely, mealy bugs and beetles were found. Fruits were found to be damaged by birds. Disease symptoms similar to canker were observed on the fruits and stem in one of the locations. Physiological disorder like yellowing during extreme summer was common in most of the orchards and these symptoms vanished immediately after a shower or with irrigation. The variability within the species was analysed using statistical techniques like factor analysis and cluster analysis. Maximum variability (59.38%) in the stem and flower characters was explained by two dimensions. The characters that contributed to the variability were intensity of red colour of bract, stem waxiness, stem sturdiness, margin of rib, spine colour, bud shape, bud apex shape, number of stigma lobes, length of style and distance between areoles. Similarly, maximum variability (62.74%) in the quality attributes were contributed by the first two dimensions out of four significant dimensions. The characters responsible for creating the variability were fruit weight, position of bract towards peel, fruit width, fruit weight without peel, fruit length, flesh colour, fruit shape, width of base of bract, length of apical bract, outer TSS, TSS-acid ratio and core TSS. Cluster analysis of the qualitative traits formed six different clusters. When the mixed data with both qualitative and quantitative characters were analysed through clustering, there were three clusters based on the stem and flower characters and four clusters based on the yield and quality attributes, which indicated variability within the species. Other species of Hylocereus namely H. undatus and H. megalanthus, and other types known as Bruni and Frankis Red imported from countries like Thailand and Vietnam are also under cultivation by farmers and are getting popular in different parts of Kerala.