Within the years 1996-2005 at Plant Breeding and Acclimatization Institute, Research Division Młochów genetic variation of 2x potato was being transferred into 4x level in interploidy crosses 4x-2x. In eight crossing cycles 233 combinations of 4x progenies were obtained. Out of them 57 were used in tetraploid parental breeding lines. They were obtained among 16 diploid donors of new alleles of chosen traits and 23 tetraploid females. Efficiency of seed setting in these crosses ranged from 0.9 to 171.0 seeds per berry. As a result of selection and comparative analysis among the progenies originating from 4x-2x crosses and standard 4x-4x progenies, 2x clones were distinguished as perspective parents for tetraploid breeding. They were as follows: HT/HZ 84-PH 151, DG 88-89, DW 88-4556, DG 93-332 and DG 97-943 for processing; DG 88-89 and DW 88- 4556 for table use; HT/HZ 84-PH 151 for high starch content; DG 91-234 for resistance to Phytophthora infestans and DG 88-9 for resistance to Erwinia carotovora.
W IHAR Młochów wyselekcjonowano złożone mieszańce ziemniaka diploidalnego charakteryzujące się wysokim poziomem cech jakościowych poszukiwanych w hodowli odmian. Należą tu: niska skłonność do ciemnienia miąższu bulw po ugotowaniu i miąższu surowego, niska skłonność bulw do zielenienia pod wpływem światła, jasne chipsy z bulw przechowywanych w niskiej temperaturze oraz po rekondycjonowaniu. Cechy te zostały przekazane na poziom tetraploidalny w krzyżowaniach typu 4x-2x. Badania poszerzono o nową grupę dzikich gatunków ziemniaka diploidalnego. Wykonano preselekcję klonów, które mogą być w hodowli źródłem nieciemnienia miąższu surowego bulw, niezielenienia bulw i jasnych chipsów z bulw przechowywanych w niskiej temperaturze. Stwierdzono, że klony z S. garsiae, S. michoacanum, S. parodii i S. pinnatisectum mogą być donorami jasnej barwy chipsów z bulw przechowywanych w niskiej temperaturze. Klony należące do S. garsiae, S. kurtzianum, S. parodii, S. pinnatisectum, S. ruizceballosii i S. simplicifolium mogą być donorami niezielenienia bulw. Natomiast klony wszystkich wymienionych gatunków, za wyjątkiem S. garsiae i S. parodii stanowią dobre źródło nieciemnienia miąższu surowego bulw.
Blackleg and soft rot are two diseases of potato caused by pectinolytic bacteria of genus Pectobacterium and Dickeya. In Poland major bacteria causing these diseases are Pectobacterium atrosepticum (Pa) and Pectobacterium carotovorum subsp. Carotovorum. Potato resistance to bacteria Pa is a polygenically inherited trait. All potato cultivars are susceptible to these bacteria, but they differ in the level of susceptibility. From 2006 to 2011 394 diploid potato clones were tested for resistance to Pa. These clones have in their origin, beside Solanum tuberosum, a range of wild and primitive cultivated potato species. The resistance was evaluated in 1–9 scale, where 9 is the most resistant. In two and three-year evaluation seven diploid clones of potato have been scored 7.0. It was the highest resistance among all tested clones. The most resistant potato cultivars Gandawa, Ślęza and Glada, were scored: 5.0, 5.0 and 4.9 respectively. The most susceptible cultivar Irys was scored 2.7. Diploid potato hybrids can be used in breeding and research on the resistance to soft rot.
The task for diploid potato collection in IHAR Mtochow is the preservation of important and unique genetic biodiversity of Solanum species. The collection was formed over 30 years ago. At the beginning, the collection included various Solanum species as the sources of resistance and quality traits. Within many years, in the collection a lot of diploid clones originated from diploid parental lines conducted at Młochów and from other local and foreign centres were preserved. In 2005 the collection of diploid clones included 106 forms propagated in the field, 37 in greenhouse and 52 in in vitro culture. The largest group of field propagated clones consisted of those selected at Młochów. They are complex interspecific hybrids of Solanum, possessing in their pedigree following species: S. demissum, S. goniocalyx, S. gourlayi, S. microdontum, S. phureja, S. stenotomum, S. stoloniferum, S. verrucosum and S. yungasense. The collection clones were intensively utilized in breeding and research works.