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BREEDING OF ABIOTIC STRESSES IN

VEGETABLE CROPS

Presented by

K. Indira

VHM/10-09

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Every plant required some physical and chemical factors in

optimum amount at a right time for its proper growth and

development.

Any deviation from this optimal condition of any factor

essential for its growth will lead to aberrant change in

experience tension and this state can be referred as plantunder stress.

Stress caused by environmental factors such as droughtor extreme heat or cold or by deficiency or toxicity of

minerals is called as abiotic stress.

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Environmental factors responsible for abiotic stress

in vegetable crops:

Drought Excessive moisture

High and low temperatures

Salinity Alkalinity

Atmospheric pollutes

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Among all those factors responsible for abiotic strees themost important factors limiting productivity are drought,

heat stress and mineral stress.

About 20% of the land is limited by mineral stress, 26% by

drought stress and 15% by freezing stress (N. K. Srinivasa

Rao and R. M. Bhatt).

It has been estimated that only 10% of the worlds arable

land may be classified in a non stress category.

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Breeding methods

a. Conventional methods:

1. Selection2. Recurrent selection

3. Pedigree method

4. Back cross method5. Bulk pedigree method

6. Mass selection

7. Mutation breeding8. Interspecific hybridization

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b. Non conventional methods:

1. Tissue culture techniques

2. Molecular/ genetic marker based approaches

3. Genetic engineering techniques

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Choice of breeding method mainly depend on

Mode of reproduction

Mode of gene action Source of resistance varieties available

Priority assigned to goal

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ScreeningLewis and Christiansen advocated following three methods of

testing breeding material for stress resistance.

1. Indirect selection:- Materials are screened under naturalstress environment conditions and a variety performing wellunder such stress conditions may be considered stresstolerant.

2.Direct selection:- In this case , materials are grown underuniform stress condition for screening. This is growing oftomato in winter and summer for screening of fruit set atlow and high temperatures, respectively.

3.Controlled condition:- The most precise accurate method isto test the breeding material under controlled conditions.

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A.Drought tolerance:

Drought is the important environmental constraint thatlimits the expression of genetic potential of many crops.

Drought is the inadequacy of water availability, including

precipitation and soil moisture storage capacity, in quantityand distribution during the life cycle of a crop to restrictthe expression of its full genetic yield potential.

Plants adapt to drought by avoidance or tolerancemechanisms.

The ability of the plant to with stand low tissue water

potentials may be considered as drought tolerance.

The ability of the plant to maintain favorable internal waterbalance under stress is considered as drought avoidance.

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Type of stress W (Mpa) Reduction in RWC

Mild stress 0.1 MPa 8 -10%Moderate stress - 1.2 to -1.5 MPa >10 to < 20%

severe stress < -1.5MPa >20%

Classification of drought stress

Hsiao (1973)

Drought tolerance is achieved by the involvement and co-

ordination of several physiological attributes during thelimited water supply.

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Osmotic adjustment: It is the process in which organic solutes accumulate and

maintain the turgor of cells during limited water supply.

It can play a major role in determining the droughtresistance by

a) maintaining turgor over fluctuating soil water,

b) maintaining stomatal conductance and thusphotosynthesis.

Various compatible solutes like sugars, organic acids,amino acids, sugar alcohols or ions are responsible forosmotic adjustment.

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Great genotypic variability exists in vegetable crops forosmotic adjustment.

Genotypes with high osmotic adjustment have highdehydration tolerance and senescence may also be

delayed.

Srinivasa rao and Bhatt reported, tomato cultivars Arka

Saurabh, Pusa Early Dwarf and Sioux have better osmotic

adjustment and thus relatively higher yield in these

cultivars under stress conditions.

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Hormonal accumulation:

Water deficits exert a profound effect on hormonal

distribution, cytokinins and abscisic acid (ABA).

As a consequence of water deficit, cytokinin activity is reduced

and ABA is increased.

An increase in the levels ofABA reduces stomatal opening,

while cytokinins exerts an opposite effect. The ABA content was higher in cv. Arka Saurabh as compared

to cv. Sel.1 of tomato.

The content of ABA was almost three times higher in Arka

Saurabh, a moderately stress tolerant cultivar, as compared to

Sel-1, a sensitive cultivar under water stress.

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Proline accumulation:

Various metabolites are accumulated in the plant tissuesupon reduction in leaf water status. Of these, free prolineamino acid accumulated at very high concentrations with arapid decrease in concentration upon rehydration (Srinivasa

Rao, 1986).

Proline accumulation have been shown to be adaptivemechanism of stress tolerance. But conflicting results claim a

positive or a negative association with drought resistance.

Significant accumulation of stress induced proline wasstudied in 8 cultivars of tomato at 0, 4, 7 and 10 days ofstress (Thakur, 1991).

High proline accumulating cultivars, Rupali, Goldmaker,Vaishali and KT- 10 were found to be more susceptible toimposed levels of water stress.

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Drought resistance is measured by attributes like

germination % of seed, rate of seedling growth, stomatalcontrol of transpiration, proline content and yield underdrought conditions.

Great variation is there in the ability of genotypes totolerant different degrees of drought.

Generally, the direct selection method is used to identifyresistant accessions.

In case ofindirect selection method, tolerant accessions are

identified on the basis of high yield underdrought conditions.

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Drought resistance in tomato was assessed on the basis of

% of seed germination in sucrose solution at differentconcentrations.

The germination % of highly resistant varieties was 65% in

sucrose solution, where in other varieties, germination %

was less than 65% (Boyarshinova, G.A., 1981).

In tomato, Strain B and Pritchard exhibited the highestgermination and dry weight at the highest moisture stress.

L. pennelliihas been reported to be the prime example ofdrought resistance on the basis of plant growth.

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Saladette and two accession ofL..esculentum var.

cerasiforme were found tolerant to moisture stress up to 10days on the basis of growth rate and leaf area parameters.

The red rock tomato variety grows well under dryconditions, which is probably due to a deep tap root system

(Stoner,A.K., 1978).

In soybean, leaf-specific weight was the most important

parameter for drought stress resistance.

In Vigna unguiculata, selections from, CB 5 exhibitedgreater drought stress resistance, earlier flowering and

exhibited pod development at early stage than other

varieties (Hall,A.E., and Grantz, D.A., 1981).

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IGFRI 450 and IGFRI 437 were found to be most tolerant

varieties.

In Phaseolus vulgaris, Pinto and white half runner, and an

accession ofP. acutifolius were grown under drought stressconditions.

Proline content is the indirect method of assessing droughtresistance. Low proline accumulation was associated with

drought resistance.

In P. vulgaris, varieties likeMoruna and Aroana performed

better under drought stress and accumulated

less proline.

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Experiments conducted in water melon under desert zone

conditions concluded that drought resistance is associated

with a reduced transpiration surface, high water retention,

and closed stomata at high temperature (Malinina,M.I.,

1971).

Varieties of an extremely early type may escape drought

.

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Excessive moisture tolerance:

The nature of excessive moisture damage depends upon

crop species, varieties, age of the plant and type of soil.

It reduces oxygen supply to the plant roots which results inan accumulation of endogenous ethylene in the plant.

Under water logged condition the hormonal balancebetween root and shoot becomes upset.

In tomato, flooding drastically reduced the GA level in the

xylem sap of the plant (Reid,D.M., Crozier,A., Harvey,

B.M.R., 1969).

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Genotypic variation for susceptibility to flooding injury hasbeen noticed in lycopersicon.

A total of 4630 accessions were screened and flood

tolerance was maximum in 8 accessions i.e ,lycopersicon

esculentum L-123, L-125, L-973, L-3072, L-3091, L4313, L-

4360 and L. pimpinellifolium L-4422.

In Tomato, Nagcarlan a primitive cultivar from Philippine

LA 1421, member of the cerasiforme has

been found tolerant to excessive moisture.

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In soybean, 20 varieties were screened under flooded

conditions, of which six varieties were comparativelysuperior for yield under water logged conditions

(Matsukawa,I., Tanimura, Y.., and Banba,H..,).

Varieties resistant to excessive moisture also showed the

most rapid conversion of ethylene to ethylene oxide.

In Vicia faba, water logged susceptible varieties yield

measurable amount of ethylene oxide(Dodds,

J.H.,Smith,A.R., and Hall,M.A.,).

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Temperature tolerance Heat tolerance: Heat tolerance is measured by the ability of the

plant to grow under high temperature conditions.

Heat resistance is a genetically controlled attribute.

Heat to erance as een stu ie in So anum tu erosum

(Khurana, S.C., and Terekhina, L.N., 1982).

Potato leaf cuttings are used for heat tolerance studies in

screening technique. Wild and cultivated species havebeen tested for heat and frost resistance.

S. tuberosum was more heat tolerant than wild species.

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Recurrent selection has been used in potato for

developing a heat tolerant variety (Gautney, T.L.,

and Haynes, F.L., 1983).

In tomato fruit set due to high temperatures is a general

problem in tropical and sub tropical countries. When thetemperature exceeds 32C, the fruit set is reduced.

,

the ability of a plant to set the fruits at a high temperature.

Adverse effect of high temperature on fruit set is of

extensively studied at 40C, ovule abortion and endospermdegeneration was observed by iwahori

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There is a great variation among the tomato accessions inthe ability to set fruits at high temperatures.

Variety Hs-102 had the ability to set fruits in April whentemperature is about 35 to 38C. However no accessionset fruit in may- June.

BL-6807, a cold set selection, had the highest ability to setfruit when pollen was exposed to high temperature.

Saladette developed by Paul leeper in Texas, is heattolerant.

UC-82B is comparatively less heat tolerant than Saladette.

The heat tolerance increased much faster in Saladettethan in UC-82B after exposure to 35C.

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In Saladette, there was normal endothecium formation in

anthers at high temperatures which is essential forstamen and pollen thecae opening, which helps inpollination.

Six varieties have been studied for pollen weight perflower which is drastically reduced at high temperatures.The maximum quantity of pollen was found in varietysa a e e.

Heat tolerance exhibited low heritability and was highlyinfluenced by environmental factors, thus indicating less

scope for selection.

Mass and pedigree methods are used in tomato.

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In Phaseolus vulgaris, high temperatures drasticallyreduced the number of pods.

Among Phaseolus species, Phaseolus coccineus was more

sensitive and P. vulgaris was heat tolerant .

.

heritability ranged from 2.9 to24%.

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In Vigna unguiculata, abscission of flowers at high

temperatures is very common.

Indehiscence of the anther and low pollen viability are the

main reasons for flower abscission.

Screening studies have indicated that the genotypes- Tvu

4552, PI 204647, and prima set pods at high temperatureswhereas, the other 55 genotypes flowered with none or a

few pods produced.

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Cold tolerance:

A temperature of0C or below causes severedamage in tropical and sub tropical crops like

tomato, egg plant, cucurbits, okra and beans.

Low temperature cause injury mainly to germination, growth,

fruit set and yield when seed or plant of a chill sensitive crop is

exposed to chilling temperatures.

Potato, tomato, bean and cucurbits do not resist temperatures

below -2 to -3C and exhibits frost injury symptoms. Whereas

cole crops, spinach and peas can tolerate frost up to -3 to -5C.

Cold tolerance is measured by the ability to germinate the

seed, to set fruit at low temperatures and to withstand chilling

temperatures

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Low temperature germination:

Optimum temperature required for uniform quickgermination is about 15 to 25C for most of the vegetable

crops.

If temperature goes down to 15C there is a reduction in

seed germination and it is drastically reduced at 10C or

below.

Low temperature seed germination is a heritable

characteristic and was controlled by additive gene action.

In Lycopersicon, it is mostly controlled by recessive factors

and in muskmelon by dominant factors

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The seeds of tomato genotypes widely differ in their

ability to germinate at a low temperature.

Eight accessions, including five wild types, were screened

at low temperatures. One accession ofL. Chilense LA 460and one accession ofL. Peruvianum PI 126435 germinated

rapidly at 10C (Scott, S.J., and Jones, R.A., 1983).

In Hisar, the temperatures in winter is very low and there

is a problem of seed germination. All the germplasm were

screened and only L.hirstum f.glabratum germinated and

grew well under such conditions

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There is a significant variation among the varieties ofcucumber for germination from 15 to 35 C.

19 varieties, 8 breeding lines, and 176 introductions were

screened, of which 5 varieties germinated at moderately

low temperature (Wehner, T.C., 1982).

Over 7000 accessions ofcucumis melo were screened forgermination and development at 15C, of these, 4 were

found promising ( Hutton,M.G. and

Loy, J.B., 1982)

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Mass selection and recurrent selection can be followed for

the improvement of germination at low temperatures.

The ability to germinate at low temperatures was improved

when mass selection was followed for 4 years in cucumber

(Schulte, H.K., and Grote, U., 1974).

.

effective in improving the germination %at suboptimal temperatures (15C)

in cucumber.

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Low temperature fruit set:

Cold tolerance is also measured by the ability to set fruitsunder low temperature conditions.

The normal temperatures for fruit set is from 15 to 25C,depending upon the variety.

A temperature below 10 C limits the fruit set.

Poor fruit set at low temperature is due to poor anther

dehiscence, poor pollination, poor pollen viability andslow pollen tube growth. Hence artificial pollination isrequired for good fruit set.

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In Hisar, maximum fruit set has been recorded at January in anaccession oflycopersicon pimpinellifolium and now it is used todevelop a cold tolerant variety (Kalloo and Banerjee, M.K., 1970).

Under Hisar conditions, varieties like Cold set, Ostenkinskiz,Montfavet, and Precoce, exhibited better fruit set in winter.

Cold set and Precoce varieties have good fruit set but because oftheir small fruit size they have less economic value. Hence thesecan be used only in hybridization.

A parthenocarpic variety may have better scope for fruit setunder low temperature conditions which is controlled by patgene.

Severianin exhibits facultative parthenocarpy and is usedin cold-resistant breeding program.

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Chilling tolerance:

L. esculentum is highly sensitive to chilling temperatures .If temperature goes down to10C the growth of the plantalmost ceases. For optimum growth, an 18C nighttemperature is required.

L. hirsutum from high elevation can tolerate as lowtemperature as 6C.

The seedling ofL. hirstum, LA 1363, developed the firsttrue leaf even at 0 C and a day temp of 20C, where asL.esculentum variety failed to develop its first true leafunder these conditions.

The chilling resistance ofL.hirsutum is heritable and can betransferred to L.esculentum (B.D. Patterson, R. Paull andR.M. Smillie , 1978).

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In carrot, chantenay, group roots, less ice was

formed and phloem and the skin was rarely

spilt by ice formation.

In celery, winter hardiness is studied in red and whitecommercial varieties.

Red varieties showed better survival rates than whitevarieties at low temperatures.

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Pea genotypes were Screened for studying winter hardiness

at -9C which eliminated all the spring varieties.

Romack ID 89-1 and C8M23 had the intermediate

hardiness characteristics.

A winter hardy field pea variety Austrian Winter, with a

- . , .

Selection at a low temperature and acclimatization under low

temperatures are required to develop a cold tolerant variety.

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Frost tolerance:

Potato is susceptible to frost but a number of genotypesshowing resistance to frost have been reported.

Frost resistance in potato is controlled by four independentgenes.

Screening or rost to erance in potato is possi e y t e

temperature induced chlorophyll fluorescence method

(sundbon, E. and Halligren, J.B., 1982).

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A high degree of resistance was shown by Solanum

depexum, S. aemulens, and S .punea but the species differ

in capacity for regeneration.

S. phujera & S. stenototum had high regeneration ability.

But in S. rybinii, only about a 25% regeneration ability was

present (M.A. Vavilova and S.A. Anikina, 1980).

Frost resistant species had higher content of easily

extractable forms of chlorophyll and carotenoids as

compared to non hardy species.

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The backcross method was used to develop a frost resistant

variety.

In the cross ofS. tuberosum and S. megistacrolobum, back

cross to S. tuberosum produced the line which is resistant tofrost and phytophthora.

In sweet potato, sugar and dry matter content of the tuberswas positively associated the degree of low temperature

tolerance.

In tomato, L. hirstum f. glabratum and L. pimpinellifolium

survived against frost.

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Salt tolerance:

The degree to which growth and normal metabolism of

plant can be maintained in saline soils is described as salt

tolerance.

Increasing salinity of the soil has become a serious problem

in arid and semi arid regions and thus limits the production

o vegeta e crops.

Improvement of salt tolerance in the cultivated

species is economical to grow crops

under saline conditions.

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In L. esculentum screening studies have not results any

satisfactory degree of tolerance. Therefore wild specieswere included in the screening program.

In L. peruvianum and L. esculentum minor there was noreduction in fruit size but L. esculentum show considerable

reduction in fruit size under saline conditions (Tal.,M. 1971).

According to Rush and Epstein, the biotypes ofL. cheesmani

can survive in full strength sea water in a hydroponic

medium, where as L. esculentum cannot sustain even half

strength.

Tolerance was associated with the ability of the cells to

cope with increased sodium levels.

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Salt tolerance in Lycopersicon is a heritablecharacteristic (Rush D.W. and Epstein,E., 1981).

The segregating population between Lycopersiconcheesmanii, a tolerant and L. esculentum, a susceptible

genotype indicated that tolerance is genetically

.

In cucurbitaceous crops seed germination was reduced

with increasing of salinity in the order

Luffa> bottle gourd> round gourd > water melon > bittergourd > musk melon (Mangal and singh, 1985)

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Abelmoschus esculentus is sensitive to salinity. Six

varieties were screened at 4.2, 7.8, 11.6 &16.3mmhos/cm.

Pusa sawani was found to be most tolerant to salinity

among other varieties for germination and vegetative

growth. This variety can be grown in soil having salinity

levels u to 6mmhos/cm with Nacl and 8mmhos/cm

NaSO4 without significant lose in yield and quality(Mangal, J.L., 1971).

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In Aliium cepa, 30 varieties were screened at 4.0, 7.5, and

11.0 mmhos/cm. Salt concentrations >4mmhos/cm reducesthe germination. Varieties Hisar-2, Punjab selection, and

Udaipur 102 were found to be most tolerant to salinity.

Pea varieties were screened at 4, 6, 8, and 12mmhos/cm. In

Pea varieties, New line perfection, Market prize, and

be grown under moderate saline conditions.

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Name of

crop

Variety Name of

chemical/

growth

substance

Concentrat

ion

Method of

treatment

Time for

treatment

(hr)

Reference

Cauli-

flower

Hisar-1 Cycocel 250ppm Root

dipping

2 Singh &

Mangal

Salt tolerance induction in some vegetable crops

1982

Okra Pusa

sawani

Cycocel 500ppm Seed

soaking

6 Mangal et

al, (1988)

Onion Hisar-2 Cycocel 1% Root

dipping

8 Malik,

(1973)

Potato Kufri

badshah

Sodium

salt or

cycocel

6 ds/m EC

or 250 ppm

Tuber

soaking

2 Yadav et al,

(1991)

Tomato Sel-7 Sodium

salts

8 ds/m EC Root

dipping

2 Mangal et

al, (1988)

H bi id l t l

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Herbicidal tolerance:

Vegetables are susceptible to herbicides applied at preand post emergence stages. There is a varietal differences

in certain vegetable crops.

15 varieties oftomato were treated with metribuzin, a

member of triazine at the true three leaf stage. The

varieties Vision H 1 vision and fire ball were found to

be tolerant.

Tolerance to metribuzin in tomato increases with seedling

age. 'Heinz 1706 was susceptible at 2 weeks age but

tolerant at 4 weeks seedling stage (Dorairaj etal., 1983).

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In soybean, the variety hood was found to be tolerant tometribuzin whereas coker 102 was susceptible.

Triazine tolerance was studied in C. sativus, the progeny ofPI 390244 showed tolerance to the application of triazine

( Gray, D., 1980).

o The Brassica napus x B.oleracea hybrid showed resistance

to atrazine (Horn, R.S., 1980).

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Problems related to breeding for abiotic stress

Complex traits controlled by several genes

These are highly influenced by environmental factors

Poorly understood mechanisms and pathways

Varieties do not show wider adaptability

Creation ofcontrolled atmosphere is problem

Poor heritability because of gene interactions

Cross signalling between biotic and abiotic factors

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Thank U