11 th conf. Agric. Dev.Res. Fac.Agric.,Ain Shams Univ. Cairo,Egypt,March,2012 Annals of Agric. Sci .Sp Issue (58) 1: 2012 Received January, 2012 Accepted February ,2012 Colonization of pepper roots with salt-tolerant PGPR as an inducer for saline stress Abou-Aly, H. E. 1 ; R. A. Zaghloul 1 ; Ehsan, A. Hanafy 1 ; A.GH. Rahal 2 ; Rasha, M. El-Meihy 1 1- Fac. Agric., Benha University, Qalubia 2- Soil, Water and Environment Research Inst. Agric. Research Center, Giza ABSTRACT This study was divided into two parts, the first part was carried out in vitro to examine the ability of six salt- tolerant PGPR strains to colonize of two pepper cultivars roots namely Romy and Qarn Ghazal. Then, choosing one of these cultivars for greenhouse experiment. The second part was conducted in the experimental farm station of Fac. Agric. at Moshtohor during 2011 season to alleviate the ability of the selected PGPR strains (Bacillus megaterium D159, Paenibacillus alvie D139 and Azospirillum lipoferum D207) in combination with compost and humic acid to increase resistance of cultivated pepper under saline stress conditions and improve its productivity. The highest significant increase of macronutrients (N, P and K) uptake and photosynthetic pigments was observed in pepper inoculated with biostimulant combined with humic acid + compost. The application of humic acid combined with compost significantly decreased the proline content in pepper. On reverse, amino acids, sugars and phenols were increased with the application of PGPR combined with compost and/or humic acid. Key words: Colonization, PGPR, saline stress, proline, humic acid and pepper. INTRODUCTION Salinity is one of the most critical constraints and hampers agriculture production in many areas around the world, including Egypt. The high salt content decreases the osmotic potential of soil water and consequently, this reduces the availability of soil water for plants (Aşik et al., 2009). Because of the economic impact of stress and the large amount of energy required to alter the environment to suit the plant, it becomes increasingly important to utilize sustainable techniques for inducing salt tolerance in plants better adapted to stress (Smit et al., 2001). PGPR have positively influence plants vitality and the ability of the plants to cope with a biotic stress conditions such as drought and salinity (Nadeem et al., 2006). The interest in the consumption of pepper fruits (Capsicum annuum L.) is to a large extent, due to its content of bioactive nutrients and their importance as dietary antioxidants. The total area of cultivated pepper in Egypt for about 400 thousand fed. (Abrol et al., 2010). Sousa et al. (2008) reported that the tolerance for high salinity should be criteria for many microorganisms aiming their adaptation in saline soils and aiming their capacity of colonizing the root system. This study aimed to maximize the ability of six salt-tolerant PGPR strains to colonize pepper roots in vitro and then alleviate their ability to improve pepper productivity under saline stress in combination with compost and humic acid. MATERIALS AND METHODS Performance of PGPR strains for pepper seeds colonization in vitro Petri dishes containing filter paper were autoclaved at 120ºC for15 min. Seeds of pepper varieties namely Romy(P1) and Qarn Ghazal (P2) were agitated in 70% ethanol for 5 sec for sterilizing seeds surface. The ethanol was discarded and the seeds were rinsed with sterile water. Then filter paper was moistened about 40% (Amin et al., 2004). Ten seeds were put on the filter paper and 1ml of each PGPR strains suspension was added on seeds. The dishes were incubated at 25ºC for six days.