From domestication syndrome to breeding objective: insights into unwanted breakup in common beans to improve shattering

Context. Agronomical traits like loss of seed dispersal targeted by ancient human selection are an important milestone of crop domestication. Evolution in plant species is a result of natural and human selection at the time of domestication. Evolution leads to continued improvement of adaptive traits in almost all plant species. Aims. Pod shattering, one of the examples of convergent evolution, is defined as breaking up of the pod shell enabling the successful dispersal of seeds mainly in wild species. Since the available climate change models predict an increase in aridity, it is expected that the losses on account of shattering will be aggravated, especially in dry areas. Methods. Histological studies and biochemical parameters are increasingly used as surrogates for pod shattering response as they provide key inputs for selecting contrasting genotypes based on differential lignification, role of pectin, fibre, cellulose and total carbohydrate content as well as enzymes such as endopolygalacturonase and beta-glucanase and hormones. key results. There is diversity for level of shattering, with race Nueva Granada showing higher rates of pod shattering as compared to the Durango and Jalisco races. Genomics has helped identify several genes or quantitative trait loci (QTL) such as PDH-I, St-I, SHAT-I, WRKYI and MYB26 that are implicated in various traits related to pod shattering. Conclusions. Plant breeders need to introgress shattering resistance into commercial varieties to mitigate the imminent yield losses. Implications. This requires an in-depth knowledge of mechanistic, physiological, biochemical and the underlying genetic basis of pod shattering resistance.