Cytoplasmic Male Sterility Incidence in Potato Breeding Populations with Late Blight Resistance and Identification of Breeding Lines with a Potential Fertility Restorer Mechanism

Abstract

Cytoplasmic male sterility (CMS) in potato is a common reproductive issue in late blight breeding programs since resistant sources usually have a wild cytoplasmic background (W or D). Nevertheless, in each breeding cycle male fertile lines have been observed within D- and T-type cytoplasms, indicating the presence of a fertility restorer (Rf) mechanism. Identifying sources of Rf and complete male sterility to implement a CMS–Rf system in potato is important since hybrid breeding is a feasible breeding strategy for potato. The objective of this study was to identify male fertile breeding lines and potential Rf candidate lines in the CIP late blight breeding pipeline. We characterized male fertility/sterility-related traits on 142 breeding lines of known cytoplasmic type. We found that pollen viability is not a reliable estimate of male sterility in diverse backgrounds. Breeding lines of the T-type cytoplasmic group had higher levels of male fertility than breeding lines of the D-type cytoplasmic group. With the help of pedigree records, reproductive traits evaluations and test crosses with female clones of diverse background, we identified four male parental lines segregating for Rf and three female parental lines that generated 100% male sterile progeny. These identified lines and generated test cross progenies will be valuable to develop validation populations for mitochondrial or nuclear markers for the CMS trait and for dihaploid generation of Rf+ lines that can be later employed in diploid hybrid breeding.

Comparative Analysis of the Genetic Diversity of Chilean Cultivated Potato Based on a Molecular Study of Authentic Herbarium Specimens and Present-Day Gene Bank Accessions

“…While hybrids or varieties with S. demissum -derived D-type cytoplasm usually participate in crosses with S. tuberosum as maternal parents due to unilateral incompatibility [ 21 , 74 , 75 , 76 ] or functional pollen sterility [ 29 ]. However, more data are coming about finding efficient pollinators possessing the D-type cytoplasm [ 62 , 72 , 74 , 77 ] that could possibly be explained by the presence of functional alleles of the nuclear restorer genes [ 78 , 79 ]. At the same time, the detection of the R1 gene marker is additional but not direct evidence of introgression from S. demissum because the markers of this gene have no clear phylogenetic signals; their homologous and pseudogenes were found in other potato species [ 80 , 81 , 82 , 83 ].…”

Potato and sweetpotato breeding at the International Potato Center: approaches, outcomes and the way forward

“…Therefore, future attempts to develop dihaploid lines should take cytoplasmic factors into account to increase the likelihood of success. Santayana et al ( 2022 ) recently confirmed a male fertility restoration mechanism in certain CIP breeding lines, which may prove valuable for hybrid potato breeding that makes use of CMS. Additionally, CIP has established a collaboration with private sector to enhance its capacity in deploying diploid-based breeding strategy in East-Africa.…”

Converting Hybrid Potato Breeding Science into Practice

“…To apply CMS efficiently in a breeding program, fertility restorer genes are important, to be able to use material freely as both male and female parent in crosses. Recently, Santaya et al, showed the presence of restorer genes in populations containing Late Blight resistance genes for different wild sources [ 52 ]. However, in the case of potato, where the tubers and not the seeds are the product, male sterile hybrids can be developed, which may have the additional advantage of leaving fewer seeds and reduce volunteers.…”