Polymorphism of the KPI-A gene sequence in the potato subgenera Potatoe (sect. Petota, Estolonifera, and Lycopersicum) and Solanum

Group A Kunitz_type protease inhibitors (KPI_A) are involved in protecting potato plants from microorganisms and pests. While the nucleotide sequence is known for many KPI_A genes of various potato cultivars (Solanum tuberosum subsp. tuberosum) and a few genes of tomato (Solanum lycopersicum), there are no data on their allelic diversity in other species of the genus Solanum. KPI_A fragments were cloned, amplified, sequenced, and analyzed from plants of the subgenera Potatoe sect. Petota (five genes from S. tuberosum ssp. andigenum and two genes from S. stoloniferum) and Solanum (five genes from S. nigrum), and their consensus sequences were established. An identity of 97-100% was observed among these sequences and the KPI_A sequences of the sections Petota (cultivated potato Solanum tuberosum ssp. tuberosum) and S. etuberosum (S. palustre) The interspecific variation of KPI_A did not exceed its intraspecific variation for all but one species (S. lycopersicum). The distribution of highly variable and conserved sequences in the mature protein_coding region was the same in all of the above species. The same primers failed to amplify the homologous genes from Solanum dulcamara, S. lycopersicum, and Mandragora officinarum. Phylogenetic analysis of the KPI_A sequences showed that S. lycopersicum clustered separately from all of the other species examined, that S. nigrum clustered together with species of the sections Etuberosum and Petota, and that these species produced no species_specific clusters. Although S. nigrum is resistant to all known races of the oomycete Phytophthora infestans, which causes one of the most economically important diseases of Solanaceae, the amino acid sequences encoded by S. nigrum KPI_A differed slightly, if at all, from their counterparts of cultivated potato, which is susceptible to P. infestans infection.