Abstract
Potato is the third most important staple food crop. To address challenges associated with global food security, a hybrid potato breeding system, aimed at converting potato from a tuber-propagated tetraploid crop into a seed-propagated diploid crop through crossing inbred lines, is under development. However, given that most diploid potatoes are self-incompatible, this represents a major obstacle which needs to be addressed in order to develop inbred lines. Here, we report on a self-compatible diploid potato, RH89-039-16 (RH), which can efficiently induce a mating transition from self-incompatibility to self-compatibility, when crossed to self-incompatible lines. We identify the S-locusinhibitor (Sli) gene in RH, capable of interacting with multiple allelic variants of the pistil-specific S-ribonucleases (S-RNases). Further, Sli gene functions like a general S-RNase inhibitor, to impart SC to RH and other self-incompatible potatoes. Discovery of Sli now offers a path forward for the diploid hybrid breeding program.
Highlights
Potato is the third most important staple food crop
To explore the genetic basis underlying the SC phenotype of RH, F1 hybrids (PI 225689 × RH) from RH crossed with PI 225689, a self-incompatible diploid line (a/a) from S. tuberosum group Phureja, were evaluated for self-compatibility (Fig. 1a and Supplementary Fig. 1a)
Genetic analysis of F1 progeny established a ~1:1 segregation ratio of SC to SI (131 self-compatible plants versus 107 self-incompatible plants; χ2 = 2.42 < χ20.05 = 3.84), indicating that SC in RH is caused by a single dominant heterozygous gene (A/a) or gametophytic factor
Summary
To address challenges associated with global food security, a hybrid potato breeding system, aimed at converting potato from a tuber-propagated tetraploid crop into a seed-propagated diploid crop through crossing inbred lines, is under development. In Solanaceae, the self-incompatibility (SI) system is gametophytic and controlled by a single polymorphic locus, called Slocus[11] This locus encodes two types of determinants: female/pistil S-determinant (a cytotoxic S-ribonuclease, S-RNase)[12] and male/ pollen S-determinant (a set of pollen-specific S-locus F-box proteins, SLFs)[13]. Eggers et al reported the identification of Sli from the wild species in the Solanaceae International Online Meeting[23], the molecular mechanism of Sli was not described This wild accession produces long stolons and high levels of toxic steroidal glycoalkaloids in tubers[8,24,25], which limits its breeding potential. The molecular basis underlying the SI to SC transition in RH remains unknown, and it is unknown whether RH can transmit heritable SC to self-incompatible diploid potatoes
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