Rye has already proven to be a good donor of genes for improving important traits and diversity in wheat breeding. The agronomic advantages of wheat-rye translocations, as well as their detrimental pleiotropic effects, were shown to be dependent on the source of the transferred rye chromatin. This justifies continued effort for introgression of rye genes from various sources into various wheat backgrounds. There are still many genes of interest for wheat improvement, not yet transferred, that are available in the rye genome. This paper describes the strategy applied at the National Agricultural Research and Development Institute Fundulea (Romania), to take advantage of the existence of intensive breeding programs in both winter wheat and triticale, and presents some of the results obtained so far by applying this strategy, in obtaining lines with common bunt, barley yellow dwarf (BYDV) and other diseases resistances, as well as improved seedling vigour and crop spectral reflectance.

Common bunt and dwarf bunt, caused by Tilletia caries (DC) Tul., T. foetida (Wallr) Liro., and T. controversa, respectively, can still cause yield and quality losses, despite the availability of effective chemical treatments. Growing resistant cultivars remains the best option for economical and environmental reasons, and is the only effective alternative in organic farming. As the durability of bunt resistance has proved to be rather poor, the pyramiding of resistance genes has been envisaged as a method of extending the life of resistance genes. Molecular markers can considerably increase the efficiency of gene pyramiding, but, because incomplete expression of both susceptibility and resistance genes makes accurate phenotyping difficult, very few markers associated with bunt resistance genes have been identified to date. This is why, at the National Agricultural Research & Development Institute Fundulea-Romania, along with the breeding program for bunt resistance, research on the possible use of molecular markers for Marker Assisted Selection (MAS) was developed. Random F 5 or F 4 lines from crosses between a Bt11 line or a bunt resistant line derived from a Triticale/2 × wheat, and susceptible parents, were phenotyped under artificial inoculation conditions, and were genotyped using primers for several markers. Preliminary results suggest that the Bt11 gene is located on chromosome 3B, and may be associated with marker loci Xbarc180, Xwmc623, Xwmc808 and Xgwm285. The gene for bunt resistance transferred from Triticale (line F00628G34-1 -possessing a 1A/1R translocation) can make MAS possible by using 1R specific markers. Although these results are preliminary, they already prove to be useful for the diversification and pyramiding of bunt resistance genes in breeding for durability of bunt resistance.

No abstract

Wheat continues to be one of the most cultivated cereals in the world, and also in Romania. Leaf rust caused by Puccinia triticina reduces the wheat yield and grains quality worldwide. In the context of climate change, leaf rust has become a more important problem for both wheat growers and breeders in our country. Use of genetic resources, carrying rust resistance genes, play an important role in breeding programs leading to resistant varieties, which can have positive impact on environment and economy. Therefore, the identification of resistance genes in modern wheat cultivars and breeding lines, and then selection of the best resistance genes combination(s) are the first steps for a successful breeding program. At present, one of the best known and studied adult plant leaf rust resistance gene is Lr34 that contributes significantly to durable leaf rust resistance. The functional markers that enable early detection of this gene are a major advantage in the wheat breeding.The aim of this study was to evaluate the presence of the slow rusting resistance gene Lr34 in Romanian wheat germplasm, using cssfr4 and cssfr5 molecular markers. Screening of 47 winter bread wheat cultivars and 47 breeding lines with these markers showed the presence of the Lr34 resistant haplotype in 62% (homozygous genotypes) of the total genotypes. A high frequency (79%) of Lr34 resistance allele was found among 47 breeding lines, suggesting that maintenance of a high frequency of this allele represents a real advantage for the development of adult plant resistance in Romanian breeding programs.

Gene pyramiding is a breeding strategy whereby host resistance genes are combined together with the objective of prolonging their usefulness in crops such as wheat (Triticum aestivum) for resistance to leaf rust caused by Puccinia recondita f.sp. tritici. When genes are combined they often give reactions different from those given by each component gene alone. Effects of gene combinations in lines Lr13 + Lr34 (T34-13), Lr13 + Lr37 (T13-37) and Lr34 + Lr37 (T34-37) were compared with those of the single gene lines CT263 (Lr13)(T13), RL6058 (Lr34)(T34), RL6081 (Lr37)(T37) and the leaf rust susceptible control, Thatcher. Infection types on plants infected with pathotypes UVPrt2 or UVPrt13 in the glasshouse, and disease severity in the field, demonstrated higher levels of resistance in the combination lines T13-37 and T34-37 than in the lines with the individual genes. The absence of sporulating uredinia in these combination lines prevented quantitative measurements of components such as latent period. In the T34-13 line, no increased resistance to pathotype UVPrt13 was apparent from assessment of the infection types in the glasshouse. Precise measurements of its resistance components showed, however, that it had a longer latent period and smaller uredinia and its resistance was highly effective in the field. There was variation in leaf rust severity amongst sister lines containing both Lr13 and Lr34, suggesting that increased resistance in T13-34 may not be controlled solely by these two genes themselves. Development of fungal structures, and the incidence and area displaying a hypersensitive reaction, were assessed using UV-1A and B-2A fluorescence microscopy filter combinations. Significant restriction of fungal growth during early postinfection stages occurred in the gene combination lines T34-13, T13-37 and T34-37. Colony size in these lines was also significantly reduced compared with that in the single gene lines T13, T34, T37 and the leaf rust-susceptible Thatcher, when either or both pathotypes possessed avirulence for one of the Lr genes. In the compatible T13-34/ UVPrt13 interaction no clear histological evidence of resistance enhancement was observed. The hypersensitive reaction in Lr37 alone or in combination and with either pathotypes, and Lr13 alone or in combination and with UVPrt2 indicated that the major component of the resistance mechanism is posthaustorial. Lr34 had the lowest hypersensitive index and even less hypersensitivity was observed in the Lr34/Lr37 combination line than in Lr37 alone. There was more prehaustorial abortion of infection structures in the line T34-37 than in T34 and T37 with isolate UVPrt2 but not with UVPrt13. It did not appear that abortion of infection structures was a major component of the resistance studied.