Functional dissection of three pollen‐side quantitative trait loci against multiple stylar unilateral incompatibility mechanisms in <i>Solanum pennellii</i> <scp>LA0716</scp>

In Solanum pennellii LA0716, three stylar UI (sui) factors and one pollen UI (pui) factor were shown to be involved in S-RNase-independent unilateral incompatibility (UI). However, additional pui factor(s) and the antagonistic relationships among pui and sui factors remain to be investigated. Quantitative trait loci (QTL) mapping, functional and genetic analysis of LA0716-based crosses, and integrated multi-omics data are used to identify pui QTLs and functionally dissect pui QTLs from various types of stylar UI. In addition to the reported pui10.1 (SpFPS2), two pui QTLs (pui6.2 and pui12.1) were identified. In LA0716 styles, the three pui loci additively attenuate stylar UI, among which pui6.2 and pui12.1 appear to antagonize the sui factor, SpHT, via independent mechanisms. Furthermore, pui12.1's function was found to be conserved in the SC styles of Solanum habrochaites LA0407 and Solanum chmielewskii LA1028. Candidate genes linked to pui6.2 and pui12.1 are identified for further analysis. This study reveals several mechanisms for three newly described types of stylar UI and the corresponding pui QTLs in LA0716, which advance our understanding of the complex genetic mechanisms underlying UI in the tomato clade.