A candidate gene-based association study of introgressed pod shatter resistance in Brassica napus

Abstract

Yield losses at maturity due to unsynchronized pod shattering remain a major rapeseed  breeding challenge. Variation for shatter resistance  in the germplasm collections is  inadequate for breeding manipulations. We have recently transferred resistance to pod shattering from Brassica carinata to Brassica napus. Introgression lines (ILs) were phenotyped for shatter resistance using the pendulum machine. Introgressive breeding was successful in enhancing rupture energy in the ILs, which varied from 1.8 to 7.2 mJ for E1 and 2.7 to 6.5 mJ for E2 while the corresponding values for natural B. napus ranged from 2.2 - 3.5 mJ (E1) and 2.2 - 4.3 mJ (E2) respectively. B. carinata had an average rupture energy of 6.3 mJ (pooled over environments).  On the basis of data averaged over two environments, I2 (6.3 mJ), I3 (5.2 mJ), I8 (5.6 mJ), I22 (5.1 mJ), I32 (5.2 mJ) and I41 (5.2 mJ) appeared very promising as germplasm resources for future breeding. Significant marker trait association between candidate gene NAC and rupture energy explained 19% of variation for the trait. NDEH 3 also appeared to be associated with rupture energy under E1. These polymorphisms represent promising candidates for the development of molecular markers for marker-assisted deployment of introgressed shatter resistance.