A Comprehensive Phenotypic Investigation of the “Pod-Shattering Syndrome” in Common Bean

Abstract

Seed shattering in crops is a key domestication trait due to its relevance for seed dispersal, yield, and fundamental questions in evolution (e.g., convergent evolution). Here, we focused on pod shattering in common bean (Phaseolus vulgaris L.), the most important legume crop for human consuption in the world. With this main aim, we developed a methodological pipeline that comprises a thorough characterization under field conditions, including also the chemical composition and histological analysis of the pod valves. The pipeline was developed based on the assumption that the shattering trait itself can be treated in principle as a “syndrome” (i.e., a set of correlated different traits) at the pod level. We characterized a population of 267 introgression lines that were developed ad-hoc to study shattering in common bean. Three main objectives were sought: (1) to dissect the shattering trait into its “components,” of level (percentage of shattering pods per plant) and mode (percentage of pods with twisting or non-twisting valves); (2) to test whether shattering is associated to the chemical composition and/or the histological characteristics of the pod valves; and (3) to test the associations between shattering and other plant traits. We can conclude the following: Very high shattering levels can be achieved in different modes; shattering resistance is mainly a qualitative trait; and high shattering levels is correlated with high carbon and lignin contents of the pod valves and with specific histological charaterstics of the ventral sheath and the inner fibrous layer of the pod wall. Our data also suggest that shattering comes with a “cost,” as it is associated with low pod size, low seed weight per pod, high pod weight, and low seed to pod-valves ratio; indeed, it can be more exaustively described as a syndrome at the pod level. Our work suggests that the valve chemical composition (i.e., carbon and lignin content) can be used for a high troughput phenotyping procedures for shattering phenotyping. Finally, we believe that the application of our pipeline will greatly facilitate comparative studies among legume crops, and gene tagging.

Genomic dissection of pod shattering in common bean: mutations at non‐orthologous loci at the basis of convergent phenotypic evolution under domestication of leguminous species

“…Details of the data for the phenotypic analysis of the pod shattering of these ILs were reported in Murgia et al . (). Briefly, phenotyping was conducted under field condition of Sardinia Island (Lat.…”

“…Recently, Murgia et al . () carried out a comprehensive characterization of the pod shattering trait in common bean using a population of 257 introgression lines (ILs) that were developed with the specific purpose of studying pod shattering in P. vulgaris . They showed that this mainly behaves as a qualitative trait, with high shattering associated with a high fiber content of the pod valves and strong lignification of the ventral sheath and the inner sclerenchyma of the pod valves.…”

“…In the present study, the same population of ILs that were phenotyped by Murgia et al . () was exploited using next‐generation sequencing (NGS) strategies of pool sequencing (pool‐seq; Ferretti et al ., ) and genotype by sequencing (GBS; Poland et al ., ). To obtain the ILs, a wild‐like, highly shattering recombinant inbred line (MG38) was backcrossed with a non‐shattering Andean snap variety (MIDAS) as a recurrent parent.…”

Pod Dehiscence in Hairy Vetch (Vicia villosa Roth)

“…Consequently, genotype by environment interactions (Tukamuhabwa et al, 2002;Helms, 2011) can cloud genetic effects. More controlled measurements of PD, such as oven drying of pods to standardize moisture and/or applying force to a pod to induce dehiscence were more associated with genetic effects than measuring PD under field conditions (Weeden, 2007;Dong et al, 2016;Murgia et al, 2017;Parker et al, 2019). Such methods, particularly measuring the force needed to induce dehiscence, demand substantial phenotyping time and specialty equipment.…”

Current State and Perspectives in Population Genomics of the Common Bean

“…Wild common bean is characterized by high seed shattering, which is crucial for propagation of the progeny and to ensure high fitness of the genotypes. Conversely, the domesticated forms have partially or completely lost this seed dispersal, as lower dehiscence ensures reduction of yield losses in the field [59,60]. Rau et al [54] used an introgression line-mapping population and proposed a model with a major locus associated to the complete loss of pod shattering, which was localized to the distal part of chromosome Pv05, plus additional QTLs hypostatic to the major QTL, at which the cumulation of wild alleles increases the level and mode of seed shattering (i.e., number of shattered and twisted pods per plant).…”