Nematology, 2011, Vol. 13(5), 509-520 Comparison of host recognition, invasion, development and reproduction of Meloidogyne graminicola and M. incognita on rice and tomato Tushar K. DUTTA 1,2,∗ , Stephen J. P OWERS 1 , Brian R. KERRY 1 , Hari S. GAUR 2 and Rosane H.C. CURTIS 1 1 Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK 2 Indian Agricultural Research Institute, New Delhi-110 012, India Received: 3 June 2010; revised: 6 August 2010 Accepted for publication: 9 August 2010; available online: 16 November 2010 Summary – The rice root-knot nematode Meloidogyne graminicola normally infects rice, wheat and several other graminaceous plants. Meloidogyne incognita is a serious pest of dicotyledonous crops, although it can infect and reproduce on some cereals. This paper demonstrates and compares host recognition, development and reproduction of these two species of root-knot nematodes on rice and tomato plants. Attraction bioassays in pluronic gel clearly showed that M. incognita preferred tomato roots to rice or mustard roots, whilst M. graminicola was more attracted towards rice compared with tomato or mustard roots. Based on the attraction data from this study, it can be hypothesised that either: i) the blend of attractants and repellents are different in good and poor hosts; or ii) relatively long-range attractants, together with shorter-range repellents, might affect nematode movement patterns. Some host specific attractants might also be involved. Meloidogyne incognita was able to invade and develop to adult female but did not produce eggs in rice roots. By contrast, M. graminicola developed and reproduced faster on both rice and tomato plants compared with M. incognita. Nevertheless, second-stage juveniles of both these root-knot nematodes showed a similar pattern of distribution inside the roots, preferring to accumulate at the root tips of rice or in the vascular cylinder and cortical region of tomato. Keywords – attraction bioassay, behaviour, mustard, pluronic gel, root-knot nematodes. Root-knot nematodes are economically important pests of cereals in many countries. Meloidogyne graminicola Golden & Birchfield is the most common species of root- knot nematode infecting rice. In India, it is reported to cause 17-30% yield loss due to poorly filled kernels (Mac- Gowan, 1989). It is a serious problem in the nurseries and upland rice fields and has recently also been found to be widespread in the deepwater and irrigated rice fields in many states of India. Normally this species is found in rice, wheat and several other graminaceous plants (Gaur et al., 1993) but it has also been reported to infect certain di- cotyledonous plants (MacGowan & Langdon, 1989). An- other root-knot nematode, M. incognita (Kofoid & White) Chitwood, causes 40-46% yield loss in tomato (Bhatti & Jain, 1977; Reddy, 1985) in India and is a serious pest of dicotyledonous crops, although it occasionally infects ce- reals. ∗ Corresponding author, e-mail: nemaiari@gmail.com The present study was conducted to compare and con- trast the differences in host recognition of M. graminicola and M. incognita on rice and tomato. Tomato and rice are known to be good and poor hosts for M. incognita, re- spectively, and vice versa in the case of M. graminicola. Mustard was reported to reduce populations of M. inco- gnita (Sharma et al., 1980) and M. graminicola (Rahman, 1990) in different cropping sequences. Thus, mustard was included in the attraction assay as negative control. Attraction or movement bioassays for nematodes are frequently performed using Petri dishes containing a flat base of agar, on the surface of which the nematodes move towards or away from a test compound placed at a set point on the agar and left to set up a concentration gra- dient. Extensive and detailed analysis of behavioural re- sponses of Caenorhabditis elegans has been done using agar plates (Croll, 1970; Rutherford & Croll, 1979; An- derson et al., 1997a, b). Although such experiments may © Koninklijke Brill NV, Leiden, 2011 DOI:10.1163/138855410X528262 Also available online - www.brill.nl/nemy 509