DISEASE CONTROL Effects of antagonistic fungi, plant growth-promoting rhizobacteria, and arbuscular mycorrhizal fungi alone and in combination on the reproduction of Meloidogyne incognita and growth of tomato Zaki A. Siddiqui Æ M. Sayeed Akhtar Received: 24 February 2008 / Accepted: 17 December 2008 / Published online: 24 February 2009 Ó The Phytopathological Society of Japan and Springer 2009 Abstract Antagonistic fungi (Aspergillus niger CA and Penicillium chrysogenum CA1), plant growth-promoting rhizobacteria (PGPR) (Burkholderia cepacia 4684 and Bacillus subtilis 7612) and AM fungi (Glomus intraradices KA and Gigaspora margarita AA) were assessed alone and in combination for their effects on the growth of tomato and on the reproduction of Meloidogyne incognita in glasshouse experiments. Application of antagonistic fun- gus, PGPR, or AM fungus alone or in combination significantly increased the length and shoot dry mass of plants both with and without nematodes. The increase in shoot dry mass caused by Gl. intraradices KA in plants without nematodes was greater than that caused by PGPR or antagonistic fungi. Similarly, the increase in shoot dry mass caused by Bu. cepacia 4684 in plants with nematodes was greater than that caused by P. chrysogenum CA1. Application of Bu. cepacia 4684 caused a 36.1% increase in shoot dry mass of nematode-inoculated plants followed by Ba. subtilis 7612 (32.4%), A. niger CA (31.7%), Gl. intraradices KA (30.9%), Gi. margarita AA (29.9%) and P. chrysogenum CA1 (28.8%). Use of Bu. cepacia 4684 with A. niger CA caused a highest (65.7%) increase in shoot dry mass in nematode-inoculated plants followed by Ba. subtilis 7612 plus A. niger CA (60.9%). Burkholderia cepacia 4684 greatly reduced (39%) galling and nematode multiplication, and the reduction was even greater (73%) when applied with A. niger CA. Antagonistic fungi had no significant effect on root colonization caused by AM fungi. Applying Bu. cepacia 4684 with A. niger CA may be useful in the biocontrol of M. incognita on tomato. Keywords AM fungi Á Antagonistic fungi Á Biocontrol Á Meloidogyne incognita Á Nematode Á PGPR Á Solanum lycopersicum Introduction Tomato, Solanum lycopersicum L., is an important vege- table crop, cultivated worldwide. Yield loss due to root-knot nematodes (Meloidogyne spp.) on tomato can reach 40–46% in India (Bhatti and Jain 1977; Reddy 1985). Plants infected with Meloidogyne spp. have typical root galling. Some infected plants also express nutrient deficiency symptoms, particularly for nitrogen (Good 1968). This disease has become a major constraint to the successful cultivation of tomato in India (Siddiqui et al. 2001b). Rhizosphere microorganisms provide an initial barrier against pathogen attack to the root (Weller 1988). Of the rhizosphere organisms, antagonistic fungi have great potential against plant pathogens (Kiewnick and Sikora 2006; Papavizas 1985). Though hundreds of organisms have been reported to parasitize or prey on nematodes, fungal antagonists have been predominantly used for the biological suppression of nematodes. Several reviews have been published exclusively on fungal antagonists of nematodes (Barron 1977; Kerry 1984; Morgan-Jones and Rodrı ´guez-Ka ´bana 1988). Of the antagonistic fungi, Aspergillus and Penicillium are common genera in most agricultural fields of India. Aspergillus species are known to produce a variety of secondary metabolites and are useful in the biocontrol of nematodes (Siddiqui et al. 2004). Similarly, Penicillium spp. are also useful as antagonists of nematodes (Eapen et al. 2005). Plant growth-promoting rhizobacteria (PGPR) are free living and may impart beneficial effects on plants. PGPR Z. A. Siddiqui (&) Á M. Sayeed Akhtar Department of Botany, Aligarh Muslim University, Aligarh 202002, India e-mail: zaki_63@yahoo.co.in 123 J Gen Plant Pathol (2009) 75:144–153 DOI 10.1007/s10327-009-0154-4