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P. N. HARATHI,1 P. RAJA SEKHAR2, K. V. HARI PRASAD1, B. V. BHASKAR REDDY2 AND
B. RAVINDRA REDDY1
Dept. of Entomology, S.V. Agricultural College, ANGRAU, Tirupati-517 502, Chittoor Dt., Andhra Pradesh, 1 Regional Agricultural Research Station2, ANGRAU, Tirupati
Identification of Asian rice gall midge, Orseolia oryzae (Wood-Mason) biotype was carried out during 2016- 18 under field conditions. A set of 17 standard rice differentials representing five groups identified to characterize the prevailing rice gall midge biotypes in the country were evaluated against gall midge population at ARS, Nellore. Based on the reaction pattern of standard differentials to gall midge populations, the biotype at ARS, Nellore was not following any prescribed pattern of any of the seven identified biotypes. So, Per cent Similarity Index of the reaction pattern observed at ARS, Nellore was calculated and based on the results from the two years data, it was found that the biotype at ARS, Nellore was 70.8 per cent similar to biotype 4 and 4M.
KEY WORDS: Rice gall midge, biotypes, Cecidomyiidae, Orseolia oryzae, Oryza sativa.
Rice gall midge Orseolia oryzae (Wood-Mason) is one of the major insect pests, causing extensive dam- age in several rice growing countries of Asia viz., Thai-
land, China, Sri Lanka, India, Bangladesh, Pakistan,
Burma, Kampuchea, Indonesia, Laos, Nepal and Viet- nam. Earlier reports have documented prevalence of rice gall midge in African countries such as Sudan, Cameroon, Mali, Upper Volta, Ivory Coast, Senegal, New Guinea, Guinea – Bissau and Nigeria (Heinrichs and Pathak, 1981). It was first reported as an unidentified insect pest on rice in Monghyr district of Bihar State, India, by Riley (1881).Damage caused by rice gall midge is due to the production of a silvery-white, tubular leaf sheath gall called ‘silver shoot’ caused by the transformation of regular tillers into tubular galls, which dry off without bearing panicles. Nalini and Henry 1970, reported that gall formation is the result of suppressing differentiation of leaf primordial at the growth cone and the development of radial ridges from the innermost leaf primordium, followed by the elonga- tion of the leaf sheath. Chemical control has limitations due to internal feeding habit of the pest and the prevailing
*Corresponding author, E-mail: harathip25@gmail.com
hydrological and edaphological conditions.Extensive cul- tivation of resistant rice varieties possessing single/resis- tant gene over a large area of India resulted in rapid de- velopment of virulent gall midge biotypes capable of over- coming host plant resistance. Hence, identification of ex- isting biotype is fore most important step to formulate a best management strategy.
The investigations to identify prevailing rice gall midge biotypes at ARS, Nellore were made during kharif, 2016-17 and 2017-18. A set of 17 standard differentials
representing five groups identified to characterize the
prevailing gall midge biotypes in the country by Indian Institute of Rice Research (IIRR), Hyderabad were sown at ARS, Nellore coinciding with the peak population of rice gall midge. Single seedling of each differential of 25- 30 days old seedlings were planted in a single row con- sisting 20 hills in each row with spacing of 20 x 15 cm between rows and plants, respectively. The observations on damaged plants on hill basis and number of healthy and infested tillers (silver shoots) in 20 hills were recorded at 30 and 50 days after transplanting as per the norms recommended by IIRR, Hyderabad. The percentage of damaged plants and silver shoots were also recorded. Each entry under five groups was rated either resistant
⦁ (with less than 10% plant damage) or susceptible (S) with higher damage (Kalode and Bentur, 1989). Based on their pattern of resistance or susceptibility, the biotypes in test locations are differentiated as biotype 1 (R-R-R- R-S), biotype 2 (S-R-R-R-S), biotype 3 (R-S-R-R-S), biotype 4 (S-S-R-R-S), 4M (S-S-S-R-S), biotype 5 (R-R- R-S-S) and biotype 6 (R-S-S-S-S), (Vijaya Lakshmi et al., 2006).
When a biotype is not following any specific reaction pattern of an identified biotype, Percent similarity Index (PSI) will be calculated which aids in comparing the similarity of either Resistant (R) or susceptible (S) reaction of an existing biotype at a location to the reaction pattern of the identified biotypes. The per cent similarity index was calculated by using the formula
Percent similarity Index= (Total no. of differentials – Total No. of dissimilar reactions) x 100
Total no. of differentials
During kharif 2016-17, the pest incidence at ARS, Nellore was low to moderate. At 30 DAT, per cent silver shoot damage among the entries ranged from 0.00 to 4.6 per cent and at 50 DAT it was 0.00 to 2.70 per cent. Per cent plant damage recorded at 30 DAT and 50 DAT ranged from 0.00 to 10.0 and 0.00 to 20.00 % respectively. Nil damage was found only in RP-2333-156- 8, RP 2068-18-3-5, INRC 3021 and B 95-1. In TN 1 per
cent silver shoot damage 30 DAT and 50 DAT was 4.60 per cent and 2.70 per cent respectively, in case of per cent plant damage it was 10.00 per cent and 20 per cent respectively (Table 1).
Nil damage was observed in Phalguna at both 30 DAT and 50 DAT during kharif, 2017-18. Per cent silver shoot damage was 0.00 to 3.37 per cent and 0.00 to 4.39 per cent at 30 DAT and 50 DAT respectively. In case of the per cent plant damage, it ranged from 0.00 to 17.5 per cent and 0.00 to 22.5 per cent respectively at 30 DAT and 50 DAT respectively, while in TN 1 the per cent plant
damage recorded was 5.00 per cent and 10 per cent at 30 DAT and 50 DAT respectively. Per cent silver shoot dam- age in TN 1 was 1.16 and 2.56 per cent respectively (Table 2).
The results of the present investigations revealed that the resistance and susceptibility of differentials tested at ARS, Nellore did not exhibited any reaction pattern similar to prescribed reaction pattern of known biotypes existing in India.
Similar variable reaction patterns when studied with 14 rice differentials was observed by Annie (2004) where in the differentials in Group II viz., Phalguna (Gm2), ARC 5984 (Gm5), Bhumansan (Gm7 (t)+(Gm8(t)) were found to be resistant and CRMR 1523 of Group III showedsusceptibility with an infestation of 10.71 per cent, slightly deviating from the reaction of pattern exhibited by biotype I (R-R-R-S). Similar deviations were also re- ported by Nair and Ambika Devi (1994) and Srinivas et
In contrary, perfect reaction pattern was recorded by Vijay Kumar et al. (2008) who reported the presence of biotype I in Madikeri and Ponnampet, Kodagu, Mysore and Hassan districts of Karnataka with R-R-R-S reaction pattern when studied with 14 rice differentials.
Further studies have to be conducted to find out the biotype existing at ARS, Nellore as the data recorded was inconsistent with the prescribed biotype pattern due to the following reasons:
⦁ During 2016-17 and 2017-18, the pest incidence was low and the damage recorded in the susceptible check was below 60%. The data recorded in the field experiment is valid only when the damage in susceptible check is 60% and above.
⦁ The pest was not following any prescribed pattern of identification of a biotype resulting in variable results every year.
As no reaction pattern was observed, per cent similarity index based on ‘R’ or ‘S’ reaction in each differential was calculated. From the results of the two years data, it was found that the similarity index was 70.6 per cent similar to both biotypes 4 and 4M. (Table 3). Based on the similarity index values, it could be concluded that the biotype existing in Nellore is following the pattern nearer to biotype 4 or 4M, however further investigations need to be carried out to confirm the presence of biotype 4 or 4M at ARS, Nellore.
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Srinivas, C., Reddy, V.N., Rao, P.S and Ramesh P. 1994. Rice gall midge Orseolia oryzae (Wood-Mason) biotype in Karimnagar District, Andhra Pradesh, India. International Rice Research Notes 19(2): 14 – 15.
Vijaya Lakshmi, P., Amudhan, S., Hima Bindu, K., Cheralu, C and Bentur, J. S. 2006. A new biotype of the Asian rice gall midge Orseolia oryzae (Diptera: Cecidomyiidae) characterized from the Warangal population in Andhra Pradesh, India. International Journal of Tropical Insect Science. 26 (3): 207–211.
Vijay Kumar Lingaraj, Akshay Kumar Chakravarthy and Thyagaraj Nandipura Eregowda. 2008. Detection of Asian rice gall midge (Orseoliaoryzae) biotype 1 in the new locations of Karnataka, South India. Bulletin of Insectology. 61(2): 277-281.
Table 1: Reaction of differentials to the existing biotype at ARS, Nellore during kharif 2016-17
Note: Values in the parenthesis are Angular transformed; DAT: Days after Transplanting
Table 2: Reaction of differentials to the existing biotype at ARS, Nellore during Kharif 2017-18
Table 3. Per cent similarity index of biotype existing at ARS, Nellore in comparison with the prescribed resistance pattern proposed by IIRR, Hyderabad
