Screening for leafhopper (Empoasca flavescens) resistance in germplasm accessions of castor (Ricinus communis L.)

INTRODUCTION

Castor (Ricinus communis L.) is an important non edible oilseed crop of dry land area with huge industrial importance (Ramanjaneyulu AV et al., 2017). It is widely distributed and adapted throughout the tropics, subtropics and temperate areas due to its low demand on soil fertility, requirement of moderate rainfall, less competition with other food crops and food grade oils. Castor is grown for its seeds, which is extracted for the non-edible oil mainly used in the manufacturing of paints, lubricants, soaps, hydraulic brake fluids, polymers and per- fumery products, among others; several derivatives of castor oil are used in a variety of industries. (Anjani K., 2012). India is the major producer in the world, castor seed with a production of 17.95 lakh tonnes (lt) during 2021-22 season, against 17.89 lt in 2020-21.  (Anon, 2022). Among states, Gujarat is leading with 6.52 lakh ha (13.45 lakh tonnes) under castor followed by Rajasthan 1.77lakh ha (2.76 lakh tonnes), Andhra Pradesh 0.16 lakh ha (0.064 lakh tonnes), and Telangana 0.022 lakh ha (0.037 lakh tonnes). According to government 2^nd advance estimates, all India castor production in 2022-23 is at area 8.917 lakh ha, production 18.82 lakh tonnes. [Source: Directorate of Economics and Statistics (DES). * 2^nd Advance estimates.

Castor is attacked by insect pests right from sowing to harvesting. More than 60 species of insects and mites have been reported to cause damage to the castor crop and their related yield loss has been estimated to be about 40-89% [Lakshminarayana M and Duraimurugan P2014, Rai BK (1976), Kotle SJ (1995) ]. The seed yield losses in castor due to insect pests varied with the season, the severity of the pest and the hybrid variety of the plant (Hegde DM .,2006). The sucking pests such as leafhoppers (Empoasca flavescens), whiteflies and thrips have been known to be the most important pests attacking castor resulting in excessive loss of grain yield (Patel BC et al., 2015). 14- 15% of yield loss caused by sucking pests was recorded in Guajarat in India (Khanpara DV et al., 2002). Nymphs and adults of leafhopper suck the sap from the under surface of the leaves causing leaf margins to become yellow, curling and under severe infestation, hopper burn symptoms were also noticed (Jayaraj S 1967). The use of tolerant/resistant cultivars in the integrated pest management programmes is the most economic approach that will minimizes the number of insecticidal application and conserves the natural enemies besides preserving the environmental safety. Hence, the present study was conducted to identify resistant genotypes against leafhoppers.

MATERIALS AND METHODS

The field experiment was conducted at Regional Agricultural Research Station, Palem. A total of 100 castor germplasm accessions were screened against leafhopper which were collected from ICAR-IIOR, Rajendranagar, Hyderabad. Each accession was sown in a single row of 6 m length with the spacing of 90 cm x 60 cm in augmented block design.  The crop was raised as per the package of practices (Anon., 2013)  except the plant protection measures.

Susceptible check DPC-9 was used as an infester row and sown after every five rows of germplasm accessions. Leafhopper counts (nymph) were recorded on three leaves in each plant selecting one leaf from top (excluding 2 topmost leaves), middle (medium maturity) and bottom (leaving one or two bottom most leaves) on the main shoot. Population recorded as number of leafhoppers/3 leaves per plant and percent leaf area burnt per plant (average of 5 plants). Hopper burn injury was recorded as per the scale suggested by Anjani et al. (2018).

  Hopper burn grade: 

                   0 – No injury

                   1 – Hopper burn upto 10%

                   2 – Hopper burn 11 to 25%

                   3 – Hopper burn 26 to 50%

                   4 – Hopper burn above 50%

RESULTS AND DISSCUSSION

Out of 100 castor germplasm accessions screened 20 entries viz., RG-18, RG-311, RG-1607, RG-1624, RG-1922, RG-2746, RG-2781, RG-116, RG-2816,  RG-2822, RG-1621, RG-3080, RG-2094, RG-3445, RG-3741, RG-3795, RG-63, RG-1389-1, RG-2296 and RG-2210 did not exhibit any hopper burn (hopper burn grade 0 on 0-4 scale) and found highly resistant to leafhopper. The leafhopper population in the entries ranged from 8.8 to 27.2 leafhoppers/3 leaves/plant; whereas the susceptible check DPC-9 recorded 67.8 leafhoppers/3 leaves/plant with hopper burn grade of 4 on 0-4 scale. Thirteen entries viz., RG-19, RG-45, RG-155, RG-1647, RG-2758, RG-2800, RG-3425, RG-211, RG-2139, RG-3477, RG-29, RG-1594, RG-1663 have recorded  hopper burn grade of 1 (10% hopper burn) with low leafhopper population ranging from 17.6 to 38.8 leafhoppers/3 leaves/plant as compared to the susceptible check, DCS-9 which has recorded a hopper burn grade of 3 (51 to 75% hopper burn) with the population of 58.6 /3 leaves/plant. The incidence of leafhopper population was high in sixteen entries viz., RG-392, RG-47, RG-386, RG-2241, RG-2430, RG-104, RG-109, RG-111, RG-3548,  RG-72, RG-1437, RG-2149, RG-66, RG-380, RG-3233 and RG-1298) with leafhopper population ranging from 40.2 to 70.6 leafhoppers/3leaves/plant with hopper burn grade of 4 (76 to 100% hopper burn).

ACKNOWLEDGEMENT

Authors are thankful to the Regional Agriculture Research Station, Palem and Indian Institute of Oilseeds Research, Rajendranagar for providing the necessary facilities and the moral support to carry out this study 

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