1. M.K. Dhillon*, A.K. Tanwar, Fazil Hasan and A.P.S. Bhadauriya
Reaction of various maize genotypes against different agro-ecological populations of spotted stem borer, Chilo partellus (Swinhoe)
M.K. Dhillon*, A.K. Tanwar, Fazil Hasan and A.P.S. Bhadauriya
Division of Entomology, ICAR-Indian Agricultural Research Institute, New Delhi , India
Background
Results
Chilo partellus (Swinhoe) is one of the most serious constraints of maize and sorghum production, causing 26.7 to 80.4% yield loss under different agro-climatic conditions in India (Reddy and Zehr 2004). Despite of, many research efforts made over the past half century to identify maize genotypes resistance to stem borer, little success has been made in incorporation of resistance genes into elite cultivars. Furthermore, the genotypes identified as resistant at one location exhibit a susceptible reaction at other locations, possibly because of Genotype × Environment interactions, and existence of genetically diverse populations of C. partellus in different agroclimatic zones .
Male genitalia
The genitalia of C. partellus males obtained from different agro-eco-regions were observed for length of valva, aedeagus, tegumen and uncus using Ocular Microscope. Length of valva (F8, 32 = 2.95; P= 0.012), aedeagus (F8, 32 = 3.50; P= 0.004), tegumen (F8, 32 = 17.01; P < 0.001) and uncus (F8, 32 = 3.44; P= 0.005) of the C. partellus males varied significantly across populations obtained from different agro-eco-regions of India. Length of valva was significantly shorter in Surat and ICRISAT population as compared to other populations. Length of aedeagus of ICRISAT males was significantly shorter, while longer in the Coimbatore population. Similarly, the length of tegumen was significantly shorter in ICRISAT being on par with the males of Jhansi. Length of uncus was significantly longer in males of Hyderabad and ICRISAT populations as compared to other populations.
Aim
To investigate response of different agro-ecological population of C. partellus to various maize genotype.
Methodology
Collection of different agro-eco-populations of C. partellus
Larval and pupal cultures of C. partellus were collected from the maize and sorghum fields in various agro-eco-regions of India (Plate 1). Nucleus culture was initially reared on maize stalks till pupation, which on adult emergence were paired in oviposition cages separately. Egg laying was collected on butter papers. Neonates of respective populations were reared on artificial diet till pupation in the insect growth chamber at 27 ± 2°C and 75 ± 5% RH, and the adults thus emerged were used for these studies.
Testing the response of C. partellus to maize in field and laboratory conditions
The experiments were conducted in experimental field of Division of Entomology and
Fig. 1. Male genitalia morphometrics of different agro-ecopopulations of C. partellus
Female genitalia
The genitalia of C. partellus females obtained from different agro-eco-regions were observed for length and width of corpus bursae, length of ductus bursae and length of papillae anales using Ocular Microscope. Length of corpus bursae (F8, 32 = 2.75; P= 0.018), ductus burase (F8, 32 = 7.03; P < 0.001) and papillae anales (F8, 32 = 5.92; P < 0.001) varied significantly among all the populations obtained from different agro-eco-regions of India. However, there were no significant differences among the test populations for the width of corpus bursae. The length of corpus bursae was significantly shorter in ICRISAT females as compared to other populations, being on par with Surat females. Length of ductus bursae and papillae anales were significantly shorter in Parbhani populations, while the length of papillae anales in Delhi and Hyderabad females was on par with each other. MH AP GJ UP DL HR KR
Fig. 2. Female genitalia morphometrics of different agro-ecopopulations of C. partellus
Conclusion
Significant variations in length of valva, aedeagus, tegumen and uncus in male, and length of corpus bursae, ductus bursae and papillae anales of female moths of C. partellus from different agro-eco-populations could be due to prevailing environmental conditions in the test locations. Earlier studies have also reported variation in shape and size of genitalia within a species due to environmental factors like temperature and geography (Andrade et al. 2005; Marko, 2006). These studies have implications for mating success among adults of C. partellus in different agro-eco-regions, adaptation to varying climatic conditions, and population buildup during different cropping seasons.
References
Plate 1. Map showing various agro-eco-regions of India from where the nucleus cultures of Chilo partellus were collected (Abbreviations used in map: HR = Haryana (Hisar), DL= Delhi-NCR, UP = Uttar Pradesh (Jhansi), GJ = Gujarat (Surat), MH = Maharashtra (Parbhani), AP = Andhra Pradesh (Hyderabad, Nizamabad), KR = Karnataka (Raichur) and TN = Tamil Nadu (Coimbatore).
Andrade, C.A.C., Hatadani, L.M. and Klaczko, L.B Phenotypic plasticity of the aedeagus of Drosophila mediopunctata: Effect of the temperature. Journal of Thermal Biology 30:
Marko, M Genital variation in moths-evolutionary and systematic perspectives. Academic Dissertation, University of Oulu, Finland.
For more information write to: *M.K. Dhillon, Senior Scientist, ICAR-Indian Agricultural Research Institute, New Delhi , India
Website: