Expression divergence of FRUITFULL homeologs enhanced pod shatter resistance in Brassica napus

To improve pod shatter resistance in the important oilseed crop Brassica napus, the phenotypic diversity of B. napus was tested using 80 B. napus varieties for pod shatter resistance by a random impact test. Among these varieties, R1-1 was identified as resistant, while R2, 8908B was susceptible to shatter. To understand the molecular basis for this phenotypic difference based on the candidate gene approach, B. napus FRUITFULL (FUL) homologs were identified and characterized. Two FUL loci in the A and C genomes of B. napus were identified. In the susceptible variety, both BnaA.FUL and BnaC.FUL were expressed in the same tissues. However, the expression level of BnaC.FUL differed in varieties with different pod shatter resistance. In the most resistant variety, R1-1, only BnaA.FUL was expressed, while BnaC.FUL was silenced. Therefore, the functional divergence and differing expression of BnaX.FUL homeologs may significantly affect phenotypic variation, which is an important consequence of allopolyploid evolution. This expression level divergence may be useful for selecting pod shatter resistant lines through marker-assisted selection in B. napus-breeding programs.