Growth and yield promotion of chickpea by Pseudomonas jessenii PS06, an efficient phosphate-solubilizing bacteria.

A. Burgos¹, A. Valverde², E. Cervantes², M. Chamber¹ and J. M. Igual².

¹CIFA Las Torres-Tomejil. 41200 Alcalá del Rio. Sevilla. SPAIN.

²IRNA-CSIC. Aptdo 257. 37071 Salamanca. SPAIN.

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A very efficient phosphate-solubilizing strain of Pseudomonas jessenii, termed as PS06, was isolated from soil of the Armuña region (Salamanca, Spain) and tested as co-inoculant for chickpea cultivation by greenhouse and field trials. Treatments included combinations of two chickpea genotypes (F85-1C and ILC-482), two chickpea-nodulating rhizobia strains (Mesorhizobium mediterraneum PECA03 and Mesorhizobium loti C-2/2) and Pseudomonas jessenii PS06. Therefore, there were six inoculation treatments for each chickpea genotype: non-inoculated controls (C); single inoculations (PS06, PECA03 and C-2/2); and double inoculations (PS06+PECA03 and PS06+C-2/2).

In the greenhouse experiments, both co-inoculation treatments showed positive effects on the growth of the chickpea genotype ILC-482 (dry weight of the aerial parts); however, in the genotype F85-1C the positive effects of PS06 was shown when co-inoculated with M. loti C-2/2 but not with M. mediterraneum PECA03. In the genotype ILC-482, double inoculations yielded a number of nodules higher than in single inoculation treatments; however, the size of nodules formed by M. loti C-2/2 were smaller in the double inoculation treatment than in the single one. In the chickpea genotype ILC-482, P. jessenii PS06 increased the number of nodules only when co-inoculated with M. mediterraneum PECA03 but raised the size of the nodules formed by any of the two rhizobial strains tested. The total N fixed, determined by subtracting the total nitrogen of the control from the total nitrogen in each treatment and dividing it by the nodule fresh weight, was increased by the double inoculations in the chickpea genotype F85-1C, but only by the treatment PS06+C-2/2 in the genotype ILC-482.

In order to test these treatments under real conditions, a field trial was carried out in the experimental farm Las Torres-Tomejil (Seville, Spain). In general, there were positive effects of the co-inoculation treatments on the yield of the chickpea genotype ILC-482, but not in the genotype F85-1C. It was noteworthy the result obtained in the ILC-482 genotype by the co-inoculation treatment PS06+C-2/2, where the seed yield was almost the 50% higher than in the control treatment. In the genotype F85-1C, no positive effects due to single or double inoculations were observed. With respect to nodulation parameters, in the case of ILC-482 genotype the results are similar to those obtained in the greenhouse trial: the co-inoculation with Pseudomonas jessenii PS06 increased the number of nodules formed by M. mediterraneum PECA03 and the size of those formed by M. loti C-2/2. Therefore, the increase in the seed productions seems to be related with the positive effects of co-inoculations on nodulation. In the case of the chickpea genotype F85-1C, nodulation parameters were not related with those obtained in the greenhouse trial: co-inoculations had no effect on the formation of nodular tissue.