Genetic Variation in Wheat toward B Toxicity Tolerance

В toxicity is a worldwide problem in agricultural soils especially in dry regions of the world, specifically with alkaline soils. It has been identified that the level of В causing toxicity varies in clayey, loamy, sandy, and loamy sand soils (Robertson et al. 1975). As a large number of factors such as soil pH, lime content, agro-physiological mechanisms regulate the В use efficiency of plants, it is crucial to identify potential genotypes with positive growth response in В toxic conditions and utilize them in breeding programs. Several reports on the genetic variability in В efficiency of wheat genotypes and differences in their response to high and low В supply are available (Karaman et al. 2012) (Table 25.1).

Bread wheat is found to be more tolerant toward В toxicity as compared to durum wheat (Kalayci et al. 1998; Karaman et al. 2012; Turan et al. 2018). This may be due to lower tissue В concentration and higher agronomic efficiency (dry matter yield) in bread wheat genotypes as compared to durum wheat (Yau et al. 1995; Taban and Erdal 2000). Boron toxicity tolerance in wheat is found to be strongly associated with the less В accumulation in the tissues (Nable 1988; Reid 2010). The limited В accumulation in resistant cultivars might be due to active efflux (Schnurbusch et al. 2010), controlled absorption, or active В exclusion from the tissues.

In addition, there are varieties with higher В concentration in tissues and enhanced В toxicity tolerance simultaneously which proposes the existence of mechanism other than exclusion (Nejad et al. 2015). Moreover, the absence of a consistent relationship between the dry weight and tissue В concentration suggests the involvement of other strategies in В toxicity tolerance (Torun et al. 2006). The mechanism of В redistribution in leaf tissues from more toxic regions (cytoplasm) to less toxic regions (cell wall) may account for В toxicity tolerance in such genotypes (Reid and Fitzpatrick 2009a, 2009b). In addition, the genotypes with higher yield in a specific high В expanse may have a lower yield in another В toxic region signifying the importance of genotype-environment in В toxicity tolerance (Pallotta et al. 2014). For example, the B-tolerant wheat genotypes showing a 16% greater yield in southern Australia revealed major yield loss in northern regions (Schnurbusch et al. 2010).

Table 25.1 Wheat Genotypes Determined to Be Tolerant to В Toxicity in Previously Conducted Studies

Name of the Genotype

Type

Origin

Given В Treatment

Growth

Condition

References

Greek

I aestivum

Greece

50 mg В per L

Nutrient solution

Nable (1988)

Halbred

T. aestivum

Australia

150 mg В per kg

Soil

Pauli etal. (1988)

India 126

T. aestivum

India

150 mg В per L

Nutrient solution

Chantachume et al.

Klein Granador Lin Calel B. Inca

Argentina

(1995)

Aus 4903 Aus 4041

Australia

Turkey 1473

Turkey

G61450

Greece

ICDW 7674

Triticum

durum

Afghanistan

50 mg В per kg

Soil

Yau et al. (1997)

Bolal 2973

T. aestivum

Turkey

25 mg В per kg

Soil

Kalayci et al. (1998)

IAC 287 IAC24

T. aestivum

Brazil

2 mg В per L

Nutrient solution

Furlani et al. (2003)

Sabil-1 Stn “S"

T. durum

Syria

25 mg В per kg

Soil

Torun et al. (2006)

BDMM-98/11S

T. aestivum

Turkey

30 mg В per kg

Soil

Karaman et al. (2012)

KRL 99

T. aestivum

India

100 mM В per L

Greenhouse

Sharma et al. (2014)

BT-Schomburgk

Australia

Kharchia-65

India

AUS1473

T. aestivum

Turkey

-

-

Pallotta et al. (2014)

AUS10105

T. durum

India

AUS10344

T. durum

Iraq

AUS14010

T. durum

China

AUS 14740

T. durum

Afghanistan

Benvenuto Inca

T. aestivum

Argentina

Bolal-2973

T. aestivum

Turkey

Bonza

T. aestivum

Colombia

Etawah

T. aestivum

India

G61450

T. aestivum

Greece/ltaly

Klein Granador

T. aestivum

Argentina

Lerma 52

T. aestivum

CIMMYT/

Nepal

Mentana

T. aestivum

Italy

Carnamah

T. aestivum

Australia

Correll

T. aestivum

Australia

Currawa

T. aestivum

Australia

Dagger

T. aestivum

Australia

Espada

T. aestivum

Australia

Frame

T. aestivum

Australia

Gladius

T. aestivum

Australia

Gurkha

T. aestivum

Australia

Halberd

T. aestivum

Australia

Heron

T. aestivum

Australia

Insignia

T. aestivum

Australia

Kalka

T. durum

Australia

(Continued)

Table 25.1 (Continued) Wheat Genotypes Determined to Be Tolerant to В Toxicity in Previously Conducted Studies

Name of the Genotype

Type

Origin

Given В Treatment

Growth

Condition

References

Arg

T. aestivum

Iran

40 mg В per kg

Soil

Nejad et al. (2015)

Krichauff

T. aestivum

Australia

Mace

T. aestivum

Australia

Matong

T. aestivum

Australia

Olympic

T. aestivum

Australia

Quadrat

T. aestivum

Australia

Spear

T. aestivum

Australia

Tjilkuri

T. durum

Australia

Wyuna

T. aestivum

Australia

Yitpi

T. aestivum

Australia

Yitpi

T. aestivum

Australia

Kalyan Sona

T. aestivum

India

133 kg H3B03

Field soil

Brdar et al. (2017)

Simonida

Serbia

per ha

Teodora

Serbia

Genetic diversity in the В tolerance level of cultivated and wild wheat genotypes has been assessed in several studies (Schnurbusch et al. 2008; Emon 2012; Emon et al. 2015). Schnurbusch et al. (2008) found that durum and bread wheat used in their experiment were more tolerant than Triticum urartu and Triticum monococcum accessions, may be due to the selection of diploid accessions for the study from an unsuitable region. In some studies, Aegilops tauschii showed the highest tolerance toward В toxicity in the screening of Aegilops sp. and Triticum sp. suggesting that D genome may also contribute toward В toxicity tolerance in wheat. This is in agreement with the concept that suggested 7B and 7D chromosomes and 5A, 5B, and 5D chromosomes of wheat that contains orthologous genes of В toxicity tolerant barley genes are linked with В toxicity tolerance (Sutton et al. 2007; Schnurbusch et al. 2008). Based on such studies, it could be proposed that a thorough screening of true genome progenitors of tetraploid and hexaploid wheat could provide more accessions with high В tolerance levels. Emon et al. (2012, 2015) conducted a series of В toxicity experiments on 12 wild wheat species including Aegilops and Triticum species with two tolerant and one susceptible bread wheat cultivars. They observed high tolerance in some of the Aegilops species and T. dicoccoides on the basis of root growth and suggested that В toxicity tolerant, Ae. longissima and Ae. sharonensis can be the potential candidates for wheat breeding programs. The results of such studies suggested that wild wheat and its relatives are the potential material for developing В toxicity tolerance in cultivated wheat genotypes.

 
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