Crop wild relatives are gaining increasing attention. Their use in plant breeding is essential to broaden the genetic basis of crops as well as to meet industrial demands, for global food security and sustainable production. Solanum malmeanum (Solanum sect. Petota, Solanaceae) is a wild relative of potatoes (S. tuberosum) from Southern South America, occurring in Argentina, Brazil, Paraguay and Uruguay. This wild potato has been largely mistaken for or historically considered as conspecific with S. commersonii. Recently, it was reinstated at the species level. Retrieving information on its traits and applied uses is challenging, because the species name has not always been applied correctly and also because species circumscriptions and morphological criteria applied to recognize it have not been consistent. To overcome these difficulties, we performed a thorough literature reference survey, herbaria specimens’ identification revision and genebank database queries to review and update the information available on this potato wild relative, contributing to an increase in research on it to fully understand and explore its potential for potato breeding. Scarce studies have been carried out concerning its reproductive biology, resistance against pests and diseases as well as tolerance to abiotic stresses and evaluation of quality traits. The scattered information available makes it less represented in genebanks and genetic studies are missing. We compile, update and present available information for S. malmeanum on taxonomy, geographical distribution, ecology, reproductive biology, relationship with its closest relatives, biotic and abiotic stresses resistance and quality traits and discuss ways to overcome sexual barriers of hybridization and future perspectives for its use in potato breeding. As a final remark, we highlight that this species’ potential uses have been neglected and must be unlocked. Thus, further studies on morphological and genetic variability with molecular tools are fundamental for an efficient conservation and applied use of this promising genetic resource.

Wild potato relatives are vital for breeding programs to tackle rising temperatures. This study proposes a methodological approach based on the examination of genetic variation among 19 accessions belonging to Solanum chacoense and Solanum commersonii from the Embrapa Potato Genebank under heat stress (HS). Heat tolerance coefficient (HTC) was calculated using genotypic values predicted through mixed models. After 15 days of heat stress (DHS), a significant variation in gas exchange and chlorophyll fluorescence indicates strong breeding potential and photosystem resilience. By 35 DHS, increased pigment variation suggests acclimation. Based on predicted genotypic values, S. chacoense outperforms S. commersonii in tuber production and gas exchange under HS, and principal component analysis (PCA) performed using the HTC shows early resistance driven by photosynthesis, mid-term by tuber yield, and long-term by gas exchange and tuber production. Genotypes BRA00167017-3, BRA00167023-1, BRA00167025-6, and BRA00167028-0 excel in heat comprehensive evaluation values (HCEVs)/comprehensive principal component value (F) rankings, demonstrating robust photosynthesis, thermoregulation, and tuber yield. Cluster analysis identifies these as highly tolerant, ideal for breeding heat-resilient potatoes. These PCA-derived weights and genotype clustering system provide a precise tool for selecting heat-tolerant wild potato germplasm, categorizing them into highly tolerant, moderately tolerant, sensitive with late recovery, and highly sensitive groups acquired for specific objectives of the breeding programs to climate change.

F1 hybrid potato breeding at the diploid level requires the development of new inbred lines from self-compatible germplasm. This study was carried out to search for new sources of self-compatible diploid wild potatoes focusing on the 1EBN species Solanum malmeanum. Five diploid accessions from Embrapa potato genebank were screened to evaluate their reproductive behavior and check if the production of viable seeds when self-pollinated results from successful fertilizations or apomixis. Measurements of the pollen were taken, and pollen viability was evaluated. Five treatments based on controlled crosses assessed gametes compatibility; response to self-pollination; occurrence of parthenocarpy and/or apomixis; and tested the accessions for autogamy and allogamy. Pollen viability vary from 96% to 100%, with viable pollen size varying from 20 µm to 22 µm. Cross-pollinations confirmed that all accessions produced viable gametes and are allogamous, since pollen tube growth confirmed fertilization in treatments where seeds were set. No accession produced parthenocarpic fruit nor apomictic seeds. Four self-pollinated accessions were self-incompatible with no fruit and seeds set. Self-incompatibility was due to a pre-zygotic barrier confirmed by inhibited pollen tube growth at 1/3 style length in BRA 00183778-0 and 2/3 in BRA 00167071-0, BRA 00167093-4, and BRA 00183754-1. One self-pollinated accession (BRA 00183755-8) produced 3 fruits totalizing 51 seeds. The self-compatibility in this accession was confirmed based on the image record of pollen tubes reaching the ovules, thus rejecting apomixis, which also did not occur in control (non-manipulated bagged flowers) and emasculated bagged flowers. The 51 endogamic seeds obtained were sown, and 17 seedlings were obtained, from which 16 tuberized. Still, further investigations are needed to elucidate the mechanism responsible for the self-compatibility, such as S-locus inhibitor (Sli), malfunction of S-RNase or HT genes.

Screening of pollen traits in diploid wild potatoes (Solanum sect. Petota, Solanaceae) is desirable to develop heat-tolerant potato (S. tuberosum) cultivars. To accomplish this goal requires exploring potato genetic resources that are conserved in genebanks. The goal of this study was to assess pollen viability and 2n pollen production of the diploid potato wild relatives under heat stress condition. We assessed pollen viability and size of nine potato accessions conserved at the Embrapa Potato Gene Bank, including eight wild potatoes S. chacoense (BRA 00167447-2, BRA 00167017-3, BRA 00167023-1, BRA 00167028-0), S. commersonii (BRA00167007-4, BRA00167420-9, BRA00183760-8), and S. malmeanum (BRA 00183755-8), along with a control accession from the cultivated species S. tuberosum (BRA 00167251-8). The plant accessions were cultivated in different growth chambers, subjected to both control temperature (ranging from 14 to 27°C) and supraoptimal temperature conditions (ranging from 24 to 34°C). At heat stress, the accessions BRA 00167251-8 did not bloom, and BRA 00167023-1 did not produce pollen. The remaining accessions did not exhibit a significant reduction in pollen viability as the temperature increased. Pollen viability at the control temperature had the lowest value in BRA-00167420-9 (S. commersonii) with 68.5% and the highest in BRA 00183755-8 (S. malmeanum) with 100%. At the supraoptimal temperature the lowest value was in BRA 00167420-9 (S. commersonii) with 54.5% and the highest in BRA 00167017-3 (S. chacoense) with 94%. The average of pollen diameter was 20 μm in all wild potato genotypes, and the increase of temperature did not lead to 2n pollen production. Estimated Genotypic Coefficient of Variation (GCV) was lower than Phenotypic Coefficient of Variation (PCV) for pollen viability. The observed heritability values ranged from 58.82% in BRA00167007-4 to 91.32% in BRA 00183755-8. Our results highlight the genetic variability available in wild potato germplasm concerning pollen viability under heat stress. Furthermore, these first insights offer valuable guidance for ongoing and future endeavors in diploid potato breeding.