Bread-making quality is a crucial trait for wheat and triticale breeding. Several genes significantly influence these characteristics, including glutenin genes and the wheat bread-making (wbm) gene. World wheat collection screening showed that only a few percent of cultivars carry the valuable wbm variant, providing a useful source for wheat breeding. In contrast, no such analysis has been performed for triticale (wheat (AABB genome) × rye (RR) amphidiploid) collections. Despite the importance of the wbm gene, information about its origin and genomic organization is lacking. Here, using modern genomic resources available for wheat and its relatives, as well as PCR screening, we aimed to examine the evolution of the wbm gene and its appearance in the triticale genotype collection. Bioinformatics analysis revealed that the wheat Chinese Spring genome does not have the wbm gene but instead possesses the orthologous gene, called wbm-like located on chromosome 7A. The analysis of upstream and downstream regions revealed the insertion of LINE1 (Long Interspersed Nuclear Elements) retrotransposons and Mutator DNA transposon in close vicinity to wbm-like. Comparative analysis of the wbm-like region in wheat genotypes and closely related species showed low similarity between the wbm locus and other sequences, suggesting that wbm originated via introgression from unknown species. PCR markers were developed to distinguish wbm and wbm-like sequences, and triticale collection was screened resulting in the detection of three genotypes carrying wbm-specific introgression, providing a useful source for triticale breeding programs.

Research into molecular mechanisms of self-incompatibility (SI) in plants can be observed in representatives of various families, including Solanaceae. Earlier studies of the mechanisms of S-RNase-based SI in petunia (Petunia hybrida E. Vilm.) demonstrate that programmed cell death (PCD) is an SI factor. These studies suggest that the phytohormon cytokinin (CK) is putative activator of caspase-like proteases (CLPs). In this work, data confirming this hypothesis were obtained in two model objects—petunia and tomato (six Solanaceae representatives). The exogenous zeatin treatment of tomato and petunia stigmas before a compatible pollination activates CLPs in the pollen tubes in vivo, as shown via the intravital imaging of CLP activities. CK at any concentration slows down the germination and growth of petunia and tomato male gametophytes both in vitro and in vivo; shifts the pH of the cytoplasm (PHc) to the acid region, thereby creating the optimal conditions for CLP to function and inhibiting the F-actin formation and/or destructing the cytoskeleton in pollen tubes to point foci during SI-induced PCD; and accumulates in style tissues during SI response. The activity of the ISOPENTENYLTRANSFERASE 5 (IPT5) gene at this moment exceeds its activity in a cross-compatible pollination, and the levels of expression of the CKX1 and CKX2 genes (CK OXIDASE/DEHYDROGENASE) are significantly lower in self-incompatible pollination. All this suggests that CK plays a decisive role in the mechanism underlying SI-induced PCD.

Distant hybridization is an important breeding strategy that can effectively expand the genetic pool for developing new, high-yielding, and stress-resistant cultivars. However, reproductive isolation often hinders the application of this approach. Intergeneric reproductive barriers (IRBs) manifest during pollen–pistil interactions in plants belonging to different genera, yet the mechanisms underlying these barriers remain largely unknown. In this study, we investigated pollen–pistil interactions during the progamic phase of fertilization in three Solanaceae species using several intergeneric cross combinations. Pollen of all tested species germinated on the stigma surface, grew through the stylar transmitting tissue, and ceased elongation at a distance of 300–920 µm therefrom due to the action of a reproductive barrier. We suggest that programmed cell death (PCD) is a factor contributing to IRBs in Solanaceae. The obtained data indicate that, in all cross combinations, the rejection of incompatible pollen tubes (PTs) is accompanied by increased activity of caspase-like proteases (CLPs), as confirmed by in vivo visualization of active CLPs and spectrophotometric measurement of their activity. Specifically, incompatible PT growth in stylar tissues during the first 4 h after pollination was accompanied by a five- to six-fold increase in caspase-3-like protease activity. Notably, the arrest of PT growth in distant hybridization shows striking similarity to that observed during S-RNase-based self-incompatibility (SI) in Solanaceae. We anticipate that further research will ultimately provide insights into the regulation of reproductive barriers during distant hybridization.