Sensitivity of alfalfa to acidity and aluminium (Al) toxicity in soil is the major limiting factor in broadening of its growing area. Due to lack of Al tolerance in primary alfalfa germplasm, there is a need for transfer of genes for Al tolerance from other Medicago germplasm. One of the identified sources of Al tolerance is M. sativa ssp. caerulea accession PI 464724, which was used as a female parent in our study. The objectives of this study were: (i) obtaining the tetraploid offspring from 2x–4x M. sativa ssp. caerulea – M. sativa ssp. sativa spontaneous crosses, and (ii) development of a breeding strategy for Al/acid tolerance in alfalfa, using M. sativa ssp. caerulea as a source of Al tolerance. Out of eleven fully developed plants, five were morphologically similar to M. sativa ssp. caerulae, while six plants were similar to M. sativa ssp. sativa. All tested plants were fertile, with the pollen viability ranging from 21.45 to 97.09% and the average number of ovules per plant from 8.80 to 12.29. Eleven SSR primer pairs confirmed the hybrid nature of M. sativa ssp. caerulae × M. sativa ssp. sativa offspring. Both the Cluster Analysis and the Principal Coordinates Analysis separated plants in the caerulae type from plants in the sativa type, with one exception. Strategies based on conventional and molecular marker breeding efforts could lead towards development of tolerant alfalfa cultivars and successful crop production on acidic, Al-contaminated soils.

Acidity is an environmental condition commonly encountered by lactic acid bacteria and bifidobacteria in the gastrointestinal tract and fermented foods. In the present study, 22 strains of Bifidobacterium were screened for acid tolerance in artificial gastric juice (AGJ, pH 3·0) and fermented milk. AGJ tolerance was found to be strain-specific, with a pronounced variation among the strains. Several strains with a high survival rate in AGJ that belonged to Bifid. longum, Bifid. breve and Bifid. adolescentis were selected. Among them, only strain BL1 of Bifid longum was found to possess a high survival rate in fermented milk during refrigerated storage. Strain BL1 exhibited a survival rate of more than 25% in AGJ at pH 3·0 for 2 h and maintained a viable cfu level of more than 108 per gram of product in fermented milk (pH 4·6) under refrigerated conditions for 2 weeks. The acid tolerance of strain BL1 was found to depend on the final growth pH (<4·5). Rapid loss of acid tolerance was observed when the cells were shifted from acid to neutral conditions by addition of NaOH. Strain BL1 cells were able to maintain much higher intracellular pH under acid conditions, in comparison with those of AGJ sensitive mutant (BL1-S) or cells that lost acid tolerance following pH shifting from acid to neutral conditions. These results suggested that a cytoplasmic pH homeostasis system may function in the acid tolerance response in this strain.