EDITORIAL
published: 07 July 2020
doi: 10.3389/fpls.2020.00926
Editorial: Legumes for Global Food
Security
Jose C. Jimenez-Lopez 1*, Karam B. Singh 2 , Alfonso Clemente 3 , Matthew N. Nelson 2 ,
Sergio Ochatt 4 and Penelope M. C. Smith 5
1
Department of Biochemistry, Cell & Molecular Biology of Plants, Estación Experimental del Zaidín, Spanish National
Research Council (CSIC), Granada, Spain, 2 Agriculture and Food, Commonwealth Scientific and Industrial Research
Organization (CSIRO), Perth, WA, Australia, 3 Department of Physiology and Biochemistry of Animal Nutrition, Estación
Experimental del Zaidín, Spanish National Research Council (CSIC), Granada, Spain, 4 Agroécologie, AgroSup Dijon, INRAE,
Université de Bourgogne, Dijon, France, 5 Legumes for Sustainable Agriculture, School of Life Sciences, La Trobe University,
Melbourne, VIC, Australia
Keywords: legumes, food security, legume breeding, sustainable agriculture, climate resilience, genetic resources,
environmental stresses and physiology
Editorial on the Research Topic
Legumes for Global Food Security
Edited by:
Susana Araújo,
New University of Lisbon, Portugal
Reviewed by:
Eric Von Wettberg,
University of Vermont, United States
*Correspondence:
Jose C. Jimenez-Lopez
josecarlos.jimenez@eez.csic.es
Specialty section:
This article was submitted to
Plant Breeding,
a section of the journal
Frontiers in Plant Science
Received: 07 May 2020
Accepted: 05 June 2020
Published: 07 July 2020
Citation:
Jimenez-Lopez JC, Singh KB,
Clemente A, Nelson MN, Ochatt S
and Smith PMC (2020) Editorial:
Legumes for Global Food Security.
Front. Plant Sci. 11:926.
doi: 10.3389/fpls.2020.00926
Global climatic change combined with population growth is imposing a huge pressure on demand
for agronomic resources. These effects are major threats for food security having a great impact
on the agroecosystem and generating various abiotic and biotic stresses that, in turn, trigger many
physiological and metabolic disorders in plants. These stresses reduce crop yields at precisely the
time when they need to increase to reach the demands of the increasing population. One of the
major scientific and agronomic challenges of this century is to understand and, when possible,
withstand stress so that yields are maintained, even under stressful conditions. This special issue
brings together a range of scholarly review and research articles focused on legume crops, key
components of healthy diets and productive crop rotations. Here we summarize some of the
highlights derived from the 36 articles published in this special issue.
Ribalta et al. provided novel information on the impact of growing conditions on the progress
of seed development and maturation, and also analyzed the endogenous hormone accumulation
across diverse pea genotypes, thereby providing further insights into the mechanism of hormonal
regulation of legume seed development and in vitro precocious germination.
Rani et al. have reviewed the literature relevant to the development of climate-resilient chickpea
through the exploitation of biotechnological and molecular approaches for the generation of novel
genotypes with an improved resistance to extreme temperatures and drought.
Basu et al. took a physiological approach to explore heat tolerance and grain filling in Vigna
radiata. They measured response to heat stress during the sensitive reproductive phase over 3 years
in two field locations in a panel of 116 accessions. They focused on a subset of 17 contrasting
accessions to perform heat stress experiments in controlled glasshouse conditions. The most
promising accessions could be distinguished using a set of 11 PCR-based markers. Further work
will be required to explore the genetics of heat tolerance during reproduction in this species.
Nair et al. have comprehensively reviewed the abiotic and biotic stresses that affect Vigna radiata,
many that will be relevant in a climate change situation, and addressed the challenges for breeding
of more resilient lines. Further breeding utilizing the available molecular technologies will be
essential to make the most of the advantages of this legume that is an important source of protein
for human nutrition.
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However, despite the importance of legumes for food security,
there are large gaps in our understanding of how phenology
is controlled at the molecular level in legumes. Zhang L. et al.
used a transgenic approach to investigate the mode of action
of a homologue of the Arabidopsis photoperiod response gene
CDF in Medicago. Rather than acting to suppress expression of
the floral integrator gene FT via the photoperiod gene CO (as
is the case in Arabidopsis), CDF appears to directly suppress FT
independently of CO in Medicago.
Ortega et al. analyzed two different inbred populations to
examine the genetic control of domestication-related differences
in flowering time and growth habit between domesticated
chickpea and its wild progenitor Cicer reticulatum. A single
major quantitative trait locus for flowering time under shortday conditions [Days To Flower (DTF)3A] was mapped to a 59gene interval on chromosome three containing a cluster of three
FT genes, which collectively showed upregulated expression in
domesticated relative to wild parent lines. They point to derepression of this specific gene cluster as a conserved mechanism
for achieving adaptive early phenology in temperate legumes.
The exploitation of hybrid vigor is common across many
grain and vegetable crops, yet remains under-exploited in legume
crops. Hybrid vigor can increase grain yield, broaden adaptation
and improves weed competitiveness. A major hindrance to the
development of hybrid legume varieties is the lack of malesterility systems for hybrid seed production. In this regard,
the production of engineered male sterile plants by expression
of a ribonuclease gene under the control of an anther, i.e.,
ENDOTHECIUM 1 (PsEND1),—or pollen-specific promoter
has proven to be an efficient way to generate pollen-free elite
cultivars. Roque et al. studied the genetic control of flower
development in legumes and several genes that are specifically
expressed in a determinate floral organ. Using genetic constructs
carrying the PsEND1 promoter fused to the uidA reporter
gene and to the barnase gene produces full anther ablation
at early developmental stages, preventing the production of
mature pollen grains in all plant species tested. Additional
effects with interesting biotechnological applications include
the redirection of resources to increase vegetative growth, the
reduction of the need for deadheading to extend the flowering
period and the elimination of pollen allergens in ornamental
plants. The PsEND1::barnase-barstar construct could also be
useful to generate parental lines in hybrid breeding approaches
to produce new cultivars in different legume species.
Heat stress during flowering has a detrimental effect on
legume seed yield, mainly due to irreversible loss of seed
number. In this regard, Liu et al. provided an overview
of the developmental and physiological basis of controlling
seed setting in response to heat stress, and showing that the
entire seed setting process in legume crops including male
and female gametophyte development, fertilization and early
seed/fruit development is sensitive to heat stress, particularly
male reproductive development.
In pea seeds, an important source of protein for food and feed,
N partitioning is a key component for seed quality and yield.
Lamure and Munier-Jolain investigated the effect of temperature
on N partitioning during seed filling. High temperatures have
Working with peanut, Tian et al., examined the effect on
salinity tolerance of priming 4-week-old seedlings with the green
volatile (Z)-3-Hexeny-1-yl acetate (Z-3-HAC), comparing one
salt-sensitive and one salt-tolerant peanut genotype. Z-3-HAC
primed seedlings exhibited increased relative water content,
net photosynthetic rate, maximal photochemical efficiency of
photosystem II and activities of the antioxidant enzymes;
moreover, osmolyte accumulation under salt stress and coupled
with significantly reduced reactive oxygen species, electrolyte
leakage, and malondialdehyde content compared to non-primed
plants. Z-3-HAC also increased the total length, surface area, and
volume of roots under salt conditions. Thus, Z-3-HAC generated
a priming-induced modification of the photosynthetic apparatus,
antioxidant systems, osmoregulation, and root morphology
protecting the peanut seedlings from salinity.
Working with M. truncatula and tobacco cell suspensions,
Elmaghrabi et al. observed that under high NaCl levels both
cell and nuclear size decreased but were not useful markers
of cell survival under salt stress, while nuclear marginalization,
observed for the first time concomitant with salinity in plant
cells, could be a novel and helpful morphological indicator for
acquisition of salinity tolerance and may be a common response
across eukaryotes.
Legume crops are valued in crop rotations in part due to their
ability to raise soil N levels through symbiotic nitrogen fixation
(SNF) with rhizobial species. Although extreme temperatures
may have detrimental effects on growth and development,
alfalfa is a legume crop known for its climate-resilience. Liu
et al., studied the role of symbiosis with rhizobium on the
plant’s performance under low temperature stress conditions, by
comparing plants with active or inactive nodules or no nodules at
all. They found that plant survival was higher in those with active
nodules. Irrespective of whether nodules were active or not,
nodulated plants accumulated more soluble proteins and sugars,
compared to plants without nodules, which exhibited a greater
activity of oxidation protective enzymes; rhizobia nodulation
enhanced the tolerance of plants to low temperatures through
an alteration of the expression of regulatory and metabolism
associated genes.
The common use of N fertilizers in modern agriculture has
raised the N content of many soils and may have led to weakened
selection for SNF efficiency in modern legume breeding. This
hypothesis was tested in common bean by Wilker et al.,
comparing the SNF efficiency and agronomic performance under
low soil N levels of 19 modern cultivars (bred under high soil
N conditions) to 25 heirloom varieties (bred under lower soil N
conditions). There was wide genetic variation for SNF efficiency
but on average heirloom bean varieties were not any more SNF
efficient than modern cultivars, although the best performer was
an heirloom variety. The authors advocated the incorporation of
heirloom varieties into modern bean breeding programs.
Phenological adaptation is a key aspect of crop productivity
and is highly relevant to food security in the light of changing
climates. Furthermore, flowering time is a key trait in breeding
and crop evolution, due to its importance for adaptation to
different environments and for yield. The molecular control of
flowering is now well-understood in the model plant Arabidopsis.
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factors. They identified various “ideal” genotypes as IPF-201416, KPMR-936 and IPF-2014-13, which can be recommended for
release and exploited in a resistance breeding program for the
region confronting field pea rust.
Chaudhari et al. screened a set of 340 diverse peanut
genotypes for LLS and rust resistance and yield traits across three
locations in India under natural and artificial disease epiphytotic
conditions. The study revealed significant variation among the
genotypes for LLS and rust resistance in different environments.
These data revealed significant environment (E) and genotype
× environment (G×E) interactions for both diseases indicating
differential response of genotypes in different environments. Pod
yield increase as a consequence of resistance to foliar fungal
diseases suggests the possibility of considering “foliar fungal
disease resistance” as a must-have trait in all the peanut cultivars
that will be released for cultivation in rainfed ecologies in Asia
and Africa.
Zhou et al. investigated differential expression of 10 Resistance
Gene Analogs (RGAs), which are key factors in the recognition of
plant pathogens and the signaling of inducible defenses, among
cultivated chickpea varieties which are resistant or susceptible to
the foliar disease Ascochyta blight caused by the fungus Ascochyta
rabiei (syn. Phoma rabiei). They found significant differential
expression of four RGAs that were consistently upregulated in
the most resistant genotype, ICC3996, immediately following
inoculation, when spore germination began and ahead of
penetration into the plant’s epidermal tissues. These represent
clear targets for future functional validation and potential for
selective resistance breeding for introgression into elite cultivars.
Nair et al., reviewed the progress and potential for genetic
improvement of mung bean for resistance to biotic stress
including fungal and bacterial pathogens, viruses and insects and
as for their analysis of abiotic stress discussed the constraints to
breeding to overcome these pests and pathogens.
The manuscript by Zwart et al. provided a detailed review
of resistance to nematodes in chickpea. A range of nematode
pests are major problems for chickpea with combined annual
yield losses of around 14% from root-knot, cyst and root-lesion
nematodes. Resistance to these nematode species in cultivated
chickpea (Cicer arietinum) is limited due to the narrow genetic
diversity but, as detailed in this comprehensive review, good
levels of resistance exist in a number of wild chickpea species.
However, barriers to interspecific hybridization hinder the use
of some of these wild species as sources of nematode resistance,
although others such as C. reticulatum and C. echinospermum
have been valuable sources of nematode resistance genes as well.
The review also discusses the use and potential of genomeassisted breeding strategies to improve nematode resistance
in chickpea.
Genetic and genomic resources of grain legumes are strategic
and valuable tools currently under forefront research worldwide,
bringing the knowledge and opportunity to facilitate the
identification of specific germplasm, trait mapping and allele
mining to more effectively develop biotic and abiotic-stressresistant and high quality grains for food and feed.
One of the main yield-determining traits under stress
conditions is seed weight. In this sense, Karikari et al.
a significant effect reducing the amount of N in mature seeds.
This appears to be a result of reduced sink strength for N and
reduced duration of seed filling. N seems not to be efficiently
remobilized from leaves, being particularly obvious for nitrate
fertilized plants, where although more nitrate was assimilated in
high temperatures it was not mobilized into the seeds.
Nutrient remobilization was addressed in another study
on pea by Gallardo et al. They combined investigation of N
remobilization using 15 N labeling and analysis of transcriptional
changes occurring as seed filling progresses to identify possible
transcriptional regulators of the process. The authors showed a
dynamic remobilization of N from leaves at reproductive and
vegetative nodes and later from all organs. Their parallel analysis
of the same processes in M. truncatula identified regulatory steps
that may be shared by both plants.
Cold damage has become the key limiting factor of early
sowing. Zhang H. et al. reviewed membrane lipid metabolism
and its molecular mechanism, as well as lipid signal transduction
in peanut (Arachis hypogaea L.) under cold stress to build a
foundation for explaining lipid metabolism regulation patterns
and physiological and molecular response mechanisms during
cold stress and to promote the genetic improvement of peanut
cold tolerance.
The multidimensional nature of plant-pathogen interactions
and the production of disease-resistant crop plants that are
resilient to climate change are major agricultural challenges
currently under thorough investigation. The manuscript by
Kankanala et al. reviewed how genomic approaches are
increasing our understanding of plant-pathogen interactions in
legumes. This is an important and timely review given the
major losses most legume crops face annually due to disease
issues. They comprehensively covered a range of topics in
terms of legume crops and diverse pathogens, with a major
focus on transcriptomic studies. These studies have greatly
expanded in recent years due to the increasing affordability of
next generation sequencing approaches and the production of
reference genomes for many legume crops, helping to identify a
number of potentially key genes for both resistant and susceptible
interactions. The review also looked at how genomic approaches
will facilitate breeding for resistance to pathogens in legumes by
describing some of the molecular tools to incorporate defense
related traits into breeding programs.
The manuscript by Nay et al. analyzed disease resistance
in common bean to angular leaf spot, an important disease
worldwide that is caused by the fungal pathogen, Pseuocercospora
griseola. They looked at 316 common bean lines representing a
diversity set, under both glasshouse and field conditions, with
the latter taking place at multiple sites in South America and
Africa. They used genotyping by sequencing and genome wide
association mapping to study the response of the common
bean lines to different races of the pathogen. In contrast to an
earlier work, which had identified 5 significant resistant loci, this
comprehensive study found only 2 to be important, Phg-2 and
Phg-4, with Phg-2 being effective against multiples races.
Das et al. assessed in field pea genotypes the magnitude
of environmental and genotype-by-environment interaction on
the resistance against rust notably influenced by environmental
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can be queried by a range of visualization and data exploration
tools. Built on an open-source platform, it is amenable to
community collaboration, which will help to ensure its ongoing
relevance and usefulness. This kind of resource is vital for linking
independent studies and deriving maximum value from costly
datasets generated globally.
Legumes play an important role in the sustainability of
agricultural and food systems, contributing to soil fertility and
environmental protection, as well as to food safety and nutrition.
Under this framework, the perception of Lens culinaris producers
and consumers of North America has been evaluated by Warne
et al., following agronomic, economic, and nutritional criteria.
In a survey of producers, the main agroeconomic reason to
introduce lentil in production systems was to diversify crop
rotation in order to capitalize on dryland production and serve
as a cash crop. Diversifying crop rotation improves agricultural
system robustness, increasing system resistance to biotic stresses
and resilience to abiotic disturbances favoring the constancy
of crop productivity. According to consumers’ perception, the
main reasons to include lentil in their eating habits are to
improve nutrition, the satiety feeling after intake and to support
a plant-based diet. In agreement with that, lentils like other
legumes are considered good sources of proteins, starch, fiber,
vitamins, and minerals. Scientific evidence has demonstrated
that carbohydrates resistant to digestion are the major factors
responsible for both low glycaemic index of legume foods and
consumers’ feeling of satiety. Finally, lentils might take part as a
component of a plant-based diet being an inexpensive and rich
source of high-quality proteins to assure a balanced and healthy
diet. Interestingly, the growing interest of consumers and nonconsumers to increase lentil consumption seems to be based on
environmental, economic and nutritional reasons. Suitable policy
actions might help to address emerging challenges and concepts
and open future opportunities in order to promote cultivation
and increase lentil consumption.
The review manuscript by Ojiewo et al., looked at advances in
research for nutritional quality and health benefits of groundnut
(Arachis hypogaea L.). Groundnut is an important global crop
both from a food point of view and for valuable levels of oil. This
substantial review focused on breeding and genetic engineering
approaches to improve various traits in groundnut including
aflatoxin resistance, allergen issues and increasing oleic acid
levels. The review also discussed important social approaches
that are needed in this area and current progress including the
ongoing efforts to improve distribution of good quality seed to
small stakeholder farmers in many parts of the world.
Consumers of pulse crops in many markets highly value the
appearance of the grain, with seed coat color and patterning
being key traits. Herniter et al. investigated the genetics of seed
coat patterning in cowpea using quantitative trait locus (QTL)
and candidate gene approaches. They identified three loci with
candidate genes (basic helix–loop–helix (bHLH), WD-repeat and
E3 ubiquitin ligase genes) and developed a model to show how
they interact to give the observed seed coat patterning.
Furthermore, Dakora and Belane identifying cowpea
genotypes that can enhance protein accumulation and
micronutrient density in edible leaves and seed through breeding
have studied the genetic basis of 100-seed weight for the
development of new improved soybean cultivars. They
evaluated a recombinant inbred line (NJIR4P) in four different
environments by using a high density interspecific linkage map
which allowed them to detect 19 stable QTLs distributed on 12
chromosomes in all individual environments plus combined
environments, seven of which were minor (R2 < 10%) but
novel, while eight were stably identified in more than one
environment. Of the 12 QTLs detected in this study which
co-localized with earlier reported ones having narrow genomic
regions, only 2 QTLs were major (R2 > 10%). Beneficial alleles of
all identified QTLs were derived from cultivated soybean parent
(Nannong4931). Based on PANTHER (Protein ANalysis through
Evolutionary Relationships), gene annotation information, and
literature searches, 29 genes within 5 stable QTLs were predicted
to be possible candidate genes regulating seed-weight/size
in soybean. Although their role in seed development needs
further validation, this work underlined the considerable
scope still available for the genetic improvement of 100-seed
weight in soybean using candidate gene mining and subsequent
marker-assisted breeding.
Pea has been studied as genetic model since the Eighteenth
century, with key contributions to genetics and the development
of the basic principles of heredity. The pea genome is
characterized by its large size (∼4.45 gigabases) of which ∼85%
is comprised of highly repetitive sequences. In this topic, Gali,
Tar’an et al., reports the construction of a sequence-based
physical map of the pea genome using whole-genome profiling
(WGP). This study reports a very valuable dataset that will
provide a framework to obtain a reference pea genome sequence
to further explore the genes governing major traits, including
those influencing seed yield and seed quality.
Raggi et al. focused on the genetic control of phenology
in common bean. They recorded flowering date in a panel of
192 inbred lines developed from diverse European landraces at
two sites over two seasons. They genotyped the panel using a
RADseq approach and performed a genome wide association
study (GWAS) to identify seven candidate genes that could
potentially be used as selective markers to finely control flowering
in bean breeding programs.
Gali, Sackville et al. reported on studies using genome-wide
association studies (GWAS) in field pea. They analyzed 135 pea
accessions from a range of countries across all continents. The
focus was on agronomic and seed related traits and the accessions
were first characterized using genotyping-by-sequencing (GBS)
from which a final set of 16,877 high quality SNPs were selected
for marker-trait association analysis. This led to the identification
of many SNPs with significant association with specific traits. In
some cases, these mapped to QTLs previously associated with the
specific trait. Overall, this large study generated resources that
have potential use in marker-assisted selection for accelerating
pea cultivar improvements.
Sanderson et al. described their online legume genetic and
genomic resource, KnowPulse, which they have developed to
serve legume breeding and genetic research communities. The
database hosts phenotypic, genotypic and genomic data for
chickpea, common bean, field pea, faba bean and lentil, which
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Editorial: Legumes for Global Food Security
(FP7-PEOPLE-2011-IOF) grant ref.: PIOF-GA-2011-301550 to
JJ-L and KS; by the Grains Research and Development
Corporation, including current project #9176622 to KS; by the
MINECO-AEI (ERDF co-financed grant AGL2017-83772-R) to
AC; and by the grant ARC Industrial Transformation Research
HUB IH140100013 Legumes for Sustainable Agriculture to PS.
has the potential to overcome protein-calorie malnutrition and
trace element deficiency in rural Africa.
Taken together, the 36 articles reported in this special issue
represent a substantial contribution to the advancement in our
understanding and breeding of climate-resilient legumes, and
we hope will lead to improved global food security in the
longer term.
AUTHOR CONTRIBUTIONS
Conflict of Interest: The authors declare that the research was conducted in the
absence of any commercial or financial relationships that could be construed as a
potential conflict of interest.
JJ-L, KS, AC, MN, SO, and PS have written, reviewed and edited
the original draft. All authors have approved the final manuscript.
The reviewer EW declared a past co-authorship with one of the authors
MN to the handling editor.
Copyright © 2020 Jimenez-Lopez, Singh, Clemente, Nelson, Ochatt and Smith. This
is an open-access article distributed under the terms of the Creative Commons
Attribution License (CC BY). The use, distribution or reproduction in other forums
is permitted, provided the original author(s) and the copyright owner(s) are credited
and that the original publication in this journal is cited, in accordance with accepted
academic practice. No use, distribution or reproduction is permitted which does not
comply with these terms.
FUNDING
This work was supported by MINECO — Spanish Government
grant ref.: BFU2016-77243-P, Ramón y Cajal RYC-2014-16536
to JJ-L and by European Research Program MARIE CURIE
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