Cytological Identification And Agronomical Trait Evaluation Of Aegilops Variabilis-wheat Derivatives

Aegilops species is an important source of genetic variability for wheat improvement. Aegilops variabilis (UUSVSV) originated from chromosome doubling of a natural hybrid between Ae. umbellulata (UU) with Ae. longissima (S1S1). It has lots of useful traits for wheat improvement, such as resistance to Meloidogyne naasi, Heterodera avenae (cereal cyst nematode), powdery mildew, leaf rust, and stripe rust.In this research, advanced wheat lines, derived from a cross of Ae. variabilis with susceptible bread wheat cultivar Yiyuan 2 and backcross to Yiyuan 2, were investigated by means of cytogenetics, molecular marker, and field trait analysis. The main results are as follows:The Ae. variabilis karyotype was poorly characterized by previous fluorescent in situ hybridization (FISH). In order to resolve this problem, we analyzed different FISH probes and found that the probe combination of pScl 19.2, pTa71 and pTa-713 can clearly identify each of the 14 pairs of Ae. variabilis chromosomes. We established FISH ideogram of Ae. variabilis using this probe combination.Among the analyzed 26 BC1F7 derivatives of wheat-^e. variabilis,15 lines were resistant to stripe rust. Our FISH ideogram was further used to detect the Ae. variabilis chromosome carrying stripe rust resistance using the 15 line as well as the susceptible line NZ309. We found that all the 15 lines had chromosome 2SV while NZ309 was absent for this chromosome. Therefore, the chromosome 2SV is the provider of stripe rust resistance. Out of the 15 resistant lines, three were 2SV+4SV addition lines (2n=46) and 12 were 2SV(2B) or 2SV(2D) substitution lines, confirmed by following SSR markers. In addition, we found that SSR marker gwml48 can be used to trace 2SV in common wheat background. Meanwhile, chromosome 2SV probably carried gametocidal (Gc) gene(s) since cytological instability and chromosome structural variations, including non-homologous translocations, were observed in some lines with this chromosome.Probably due to the effects of photoperiod genes, substitution lines 2SV(2D) and 2SV(2B) lines exhibited a later heading time than their sister line NZ309 without 2SV and their wheat parent Yiyuan 2. The 2SV(2D) substitution lines were significantly taller and exhibited higher spikelet numbers and longer spikes than NZ309 line. Meanwhile,2SV(2D) substitution lines has heavy waxiness, absent in parents and other lines. It seems that the loss of chromosome 2D had more obvious phenotype effects.