Determining the breeding value of CIMMYT’s International Bread Wheat Nursery (IBWSN) entries for leaf, stem and stripe rust resistance

The quest for durable rust resistance in wheat is burgeoning with the emergence of new virulent races. Breeders challenged with this unceasing plant-pathogen arms race have to devise strategies for effective evaluation and exploitation of the rust resistance genes. Considering the likely presence of useful variation for rust resistance in CIMMYT’s international bread wheat screening nurseries (IBWSN), we implemented genomic prediction in the 45th and 46th IBWSN entries to determine their genomic estimated breeding values (GEBV’s) for leaf, stem and stripe rust resistance. The 350 lines (45th IBWSN) and 329 lines (46th IBWSN) were phenotyped in replicated trials over two to three years in El Batan, Mexico (leaf rust); Njoro, Kenya (stem rust) and Toluca, Mexico (stripe rust). The filtered genotyping data for these two nurseries comprised of 6,786 and 11,218 genotyping by sequencing (GBS) markers. Our objective was to compare the GEBV’s estimated by four different models: multiple linear regression (MLR) with QTL-linked markers as fixed effects; Genomic-best linear unbiased prediction (G-BLUP); G-BLUP mixed model which includes QTL linked markers as fixed effects and Bayesian least absolute shrinkage and selection operator (LASSO). We observed that the prediction accuracies (calculated using 10-fold cross validation) were the highest for stripe rust (0.52 to 0.61), followed by stem rust (0.42 to 0.65) and leaf rust (0.15 to 0.45). Among the models, the MLR gave the lowest prediction accuracies (0.15,0.42 and 0.52), while G-BLUP (0.45,0.59 and 0.59), mixed G-BLUP (0.38,0.65 and 0.62) and the Bayesian LASSO (0.45,0.58 and 0.61) yielded relatively higher and almost similar accuracies. Overall, our results are promising and indicate that using genome-wide markers is advantageous than including only significant QTL-linked markers. We hope that implementing genomic prediction in breeding programs, would help to achieve rapid gains from selection and revolutionize our efforts in combating the rust pathogen.

Juliana
Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, USA
Primary Author Email: 
fp228@cornell.edu