Biotechnology approaches to overcome biotic and abiotic stress constraints in legumes - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 250

diseases and pod diseases attributable to at least 15
different species of fungi (Ihejirika et al., 2010). Most of
these fungal agents are soil borne and tend to affect all
the parts of the plant.

Table 15.1 Biotic and abiotic stress response factors.

Legume response to abiotic
stress factors

Legume response to biotic
stress factors

C-promoter binding proteins
(low temperature)

Chitinase (fungal infection)

15.3.1.4 Nematode and arthropod infestations
A number of worms and insects are associated with
parasitic damage to legumes. Of the many nematodes,
the most significant ones infecting legumes include
root-knot nematode ( Meloidogyne spp.), cyst nematode
( Heterodera spp.), stem nematode ( Ditylenchus spp.) and
reniform nematode ( Rotylenchulus spp.) (Lombardo et al.,
2011; Vovlas et al., 2011; Ahmed et al., 2012; Leach et al.,
2012). Nematodes, in comparison to other biotic
stresses, do not produce specific signs of infection; rather
their infection is exhibited as a delayed appearance of
normal growth characteristics, decreased ability to fix
nitrogen and retardation of development. Insect pests,
on the other hand, show conspicuous features of
damage to all the plant body parts including leaves,
stems, flowers and pods. More than 70 insect species
infect soybean crops. For example, Spodoptera litura ,
Hedylepta indicata and Mylabris pustulata have been impli-
cated in causing crop losses of up to 50% (Dialoke et al.,
2010; O'Neal & Johnson, 2010; Dung et al., 2011). Other
financially significant insects infecting legumes include
aphid, hairy caterpillar, thrips, white fly (vector of the
yellow mosaic virus), leaf hopper, army worm and
green bug (Viteri et al., 2009; Xu et al., 2010; Musser
et al., 2011; Hodgson et al., 2012; Kumar et al., 2012b;
Mehrkhou et al., 2012).

Dehydration responsive
element-binding protein (low
temperature and drought)

Taumatin gene (fungal infection)

Heat-shock factor (high
temperature)

Nod factor receptor protein
(legume-rhizobium interaction)

SQUA promoter-binding
protein-like 7 (micronutrient
deficiency)

Necrotic lesion response gene (viral
infection)

1-pyrroline-5-carboxylate
synthase (salinity)

15.3.2 abiotic stress
Abiotic stress factors include a list of all the environ-
mental and physico-chemical features that affect the
individual growth and development of a plant. These
factors usually act in combination in form of a 'stress-
matrix' resulting in heavy economic and agricultural
losses (Mittler, 2006). The common abiotic constraints
to plant growth include the high or diminished avail-
ability of nutrients and salts, altered levels of water in
the agricultural land, deviation from the optimum
growth temperatures and natural disasters, among
many other edaphic, climatic and geographical factors.

15.3.2.1 Extremes in temperature
Legumes are widely distributed among the various
geographical zones of the world and among the various
habitats. Though the plants are resistant to slight
changes in surrounding temperatures, when there is a
significant increase in temperature or the elevated tem-
perature is coupled with other stress factors, the
capability of the plants to resist harsh environmental
conditions is decreased. This, ultimately, results in a lack
of proper growth or the death of the plant. In particular,
the cold season legumes are highly sensitive to heat and
increases in temperature (Thomas, 2010). These include
the lentils, faba beans and pea varieties. Freezing or very
low temperatures coupled with frost have been associ-
ated with yield losses in warm temperate legumes
including cowpea, soybean, groundnut and mung bean
(Thakur et al., 2010).

15.3.1.5 Weeds and herbs
Unlike other biotic stress factors, weeds and herbs may
not cause direct damage to the legumes. Instead they
compete for the same resources that are available to the
cultivated plants. They affect the growth, stature, agro-
processing and overall yield of the plants. Groundnut,
lentils, soybean, pigeon pea, mung pea, black gram and
chickpea are all adversely affected by weeds, especially
when infestation takes place during the early stages of
plant life. Commonly observed weeds include various
species of Chenopodium , Avena , Sonchus , Convolvulus and
Phalaris genera (Rashid et al., 2009; Döring et al., 2012;
Šarūnaitė et al., 2012; Smitchger et al., 2012). Reduction
in yields of up to 90% have been noted owing to the
growth of weeds in case of certain legumes (Table 15.1).