POTATO ,pBppshshshhhsgpshshhREEDING.pptx

DEPARTMENT OF GENETICS AND PLANT BREEDING
COURSE TITLE: PRINCIPLES OF PLANT BREEDING II
COURSE CODE: PLB 602
CREDIT HOUR: 3 (2+1)
PRESENTATION ON: POTATO BREEDING
PRESENTED BY: AJAY KUMAR YADAV (PLB-07M-2022)
M. Sc. Ag. 1st Year 1st Semester
AGRICULTURE AND FORESTRY UNIVERSITY (AFU)
FACULTY OF AGRICULTURE
RAMPUR, CHITWAN

• Potato (Solanum tuberosum L.) is the world’s most important tuber crop.
• Most productive and widely grown food crops in the world.
• Produces approximately twice as many calories per hectare as rice or wheat.
• Adapted to a wide range of climates and can be found in both tropical and
temperate environments and at elevations from sea level to 4000m.
• Cultivated both in large tracts and in home gardens.
• Highly nutritious because it contains significant concentrations of vitamin C and
the amino acids essential for good human nutrition.
• Eedible food materials are stored in underground parts, called tubers.
• Propagated asexually or vegetatively through these tubers.
• The sprouts arise by germination of buds in the eye of the tuber
INTRODUCTION

• Belongs in the genus Solanum and the family Solanaceae.
• Genus Solanum contains approximately 2000 species, including over 150 tuber
bearing species which form a polyploid series from diploids (2x) to hexaploids (6x)
with 75% of them being diploid.
• Cultivated potato belongs to the species Solanum tuberosum and is considered to
be an autotetraploid with a genomic formula of 2n =4x=48. This is the only species
of the tuber bearing
• Solanum tuberosum is generally believed to have originated in the Andes region
from central Peru to central Bolivia (primary center of origin).
CLASSIFICATION AND CENTRES OF ORIGIN OF POTATO

Solanum tuberosum (2n = 48)
Tetraploid
Place of origin: South America.
Ancestry:
• a) Natural doubling of diploid cultivar: Solanum stenotomum (2n = 24)
• b) By a natural crossing of diploid wild species: Solanum sparsipilum and Solanum
vernerii
Classification: According Hawkes (1992) in addition to solanum tuberosum some
six other cultivated species and over 230 wild species of potato are generally
recognized.
Diploid (2n=24)
1. Solanum ajanhuiri - Frost resistant
2. Solanum phureja - Sort duration. 4 month no dormancy
3. Solanum stenotomum - Longer in duration 6 months dormancy.
CLASSIFICATION AND CENTRES OF ORIGIN OF POTATO Cont…

Triploid (2n = 36)
4. Solanum chauca
5. Solanum juseczuki
Tetraploid (2n = 48)
Solanum tuberosum
6. subspecies
Solanum tuberosum ssp tuberosum
Solanum tuberosum ssp andigena - High altitude potato
Pentaploids
7. Solanum curtilobium - Frost resistant.
CLASSIFICATION AND CENTRES OF ORIGIN OF POTATO Cont…

DETAIL OF POTATO AND TUBER MORPHOLOGY (PANDE AND LUTHRA, 2003)

DETAILS OF POTATO FLOWER, FRUIT AND SEED (PANDE AND LUTHRA, 2003)

• failure to flower,
• dropping of buds and flowers either before or after fertilization,
• low pollen production and failure to produce viable pollen,
• male sterility, and
• self-incompatibility.
OBSTACLES TO SEED PRODUCTION IN THE POTATO INCLUDE

• Potato requires long day lengths (around 16 hours), abundant rainfall, and cool
temperatures to flower.
• Under most normal growing conditions, the day lengths in the early pan of the season
will favor flowering over tuber production, which requires short days (around 12 hours).
• High heat at the time of flowering may lead to floral abscission while still in the bud
stage, giving the appearance that the cultivars don't flower well.
• While many older cultivars, in particular 'Russet Burbank,' flower sparsely and are often
male sterile, the newer cultivars usually flower abundantly and many are male fertile.
• Various techniques are often used to induce flowering such as periodic removal of
tubers, girdling or constriction of the stem, and grafting of young potato shoots onto
tomato or other compatible Solanaceous plants
FLOWERING IN POTATO

• Reduced seed set in flowers of the cultivated potato may result from male sterility or
incompatibility.
• The problem is complex, and many nuclear and cytoplasmic genetic systems are responsible.
• In certain cases, F1 progeny, which are both male and female fertile, results when reciprocal crosses
are made.
• In other crosses, male sterility occurs in the F2 progeny when the cross is made in only one
particular direction.
• Male sterile progeny may have deformed flowers with indehiscent anthers or shrivelled microspores
which do not separate.
• Failure to produce pollen, or production of poor-quality pollen, is another common cause of sterility
in S. tuberosum.
• The failure to produce pollen may be an inherent characteristic with sterility dominant to fertility.
• Presence of a tetrasomic gene, which is lethal when present in a homozygous condition, or partly
lethal when present in the heterozygous condition, has also been reported.
STERILITY AND INCOMPATIBILITY

• The tetraploid nature of potato can be exploited by the breeder to improve desirable
characteristics.
• Potato have evolved taking advantage of nonadditive or epistatic gene action.
• Therefore, the potato breeder must be knowledgeable on the use of breeding procedures that can
accommodate nonadditive gene action.
• Because of the potato's autotetraploid nature, intralocus interactions (heterozygosity) and
interlocus interactions (epistasis) are important when selecting breeding procedures to improve
certain traits.
• It is assumed that increased heterozygosity leads to increased heterosis.
• Heterosis in potato occurs when the progeny outperforms the best parent or the parents' mean.
• The level of heterozygosity is influenced by how different the four alleles are within a locus.
• The more diverse the alleles are within a locus, the higher the heterozygosity and the greater the
number of increased interlocus or epistatic interactions.
GENETICS OF POTATO

To see how increased heterozygosity can lead to more epistatic interactions, it is
necessary to identify the allelic conditions possible in an autotetraploid. Five
tetrasomic conditions are possible at an individual locus in an autotetraploid:
• a1a1a1a1, a monoallelic locus where all alleles are identical,
• a1a1a1a2, an unbalanced diallelic locus where two different alleles are present
in unequal frequency,
• a1a1a2a2, a balanced diallelic locus where two different alleles occur with equal
frequency,
• a1a1a2a3, a triallelic locus where three different alleles are present, and
• a1a2a3a4, a tetraallelic locus where four different alleles are present.
GENETICS OF POTATO Cont…

1. Breeding for high yield:
• Yield of tubers decided by number of
tubers, tuber size and distribution of
tuber.
2. Breeding for varieties having better
morphology of tuber:
• Better morphology of tuber is
determined by
a) Eye depth
b) flesh colour
c) Growth cracks
d) Hollow heart
e) Shape
f) Skin colour
BREEDING OBJECTIVES
3. Breeding for better quality:
Depends on many factors
a) After cooking blackening
b) Dry matter.
c) Enzyme browning.
d) Glycoalkaloid level
e) reducing sugar content
f) storage properties
4. Breeding for disease resistance: Early
blight, late blight, powdery scab.,
verticillium wilt, virus diseases.
Resistant source: Solanum demissum,
Solanum acaule ssp. andigena
5. Breeding for pest resistance:
Nematode is the major pest
ssp.andigena - tolerant. Solanum
verineii resistant to Aphids, Colorado
6. Breeding for tolerance
to high temperature and
heat
7. Breeding for frost
resistance
8. Breeding for drought
resistance

CONVENTIONAL BREEDING APPROACHES:
• Potato is highly heterozygous plant.
• Potato breeding has been a cumbersome task due to inherent biological factors,
cytoplasmic nuclear sterilities, tetrasomic inheritance and inbreeding depression.
• Mainlydepends on the identification of promising parental lines for making
desired crosses, creation of variation through crossing and subsequently selection
of desirable recombinants for further evaluation and vegetative propagation.
• Although the wild and primitive species open new opportunities for the potato
breeder, but use of such species introduce a lot of genetic loads with one or few
unwanted characters. These unwanted characters are to be eliminated through
successive backcrosses
METHODS OF IMPROVEMENT OR BREEDING METHODS OF POTATO

1. Pre-breeding:
• Practiced with aim of improving the agronomic features of wild species and to
incorporate multiple resistance in the parental lines.
• For incorporating many characteristics in a cultivar, it is important to develop multiplex
parents.
• This involves crossing at different ploidy levels, doubling of chromosomes, and use of
bridging species to overcome crossability barriers.
• The use of parents that are quadruplex for a major resistance gene would ensure that all
of their progeny would be resistant.
• Even duplex parents would have more probability of passing their resistance to the
progeny as compared to triplex parents.
METHODS OF IMPROVEMENT OR BREEDING METHODS OF POTATO Cont…

2. Neo-tuberosum:
For broadening the genetic base of the potato, Neo-tuberosum could be used.
In this, S. tuberosum ssp. andigena which is short day adapted, is selected for long
days.
This scheme is directed towards wholesome utilization of the total andigena
genotypes.
The scheme is based on theory that andigena is rich source of genetic variability.
Andigena is particularly useful for breeding varieties for short days conditions.
Tuberosum x Andigena crosses are known to result in heterosis for tuber yield and its
components, though late maturity and undesirable attributes are observed in the
progenies.

3. Phenotypic expression:
• Choice of parent is most often based on its de facto phenotypic expression of the characters of
interest.
• Normally breeders try to pick pairs of clones/varieties for inter-mating based on complimentary
sets of characters with desirable level of expression.
• Breeders generally try to use improved clones or varieties as parents because these are taken to
be of acceptable "horticultural types".
• However, the choice of parents based merely on phenotypic expression of desired characters, is
sometimes ineffective particularly when non-additive gene action is significant for the trait of
interest.
• Clones or varieties that appear to give a higher proportion of clones within acceptable limits,
among their progenies, can be made use in future breeding programmes.

4. Mid-parent values:
• The mid-parental values should provide a good prediction of the mean performance of the progeny,
if parental general combining ability effects are highly correlated with their phenotypes.
• As mid-parent values are based on the phenotypic performance of the parents, this may or may not
be reflected in their progeny.
5. Specific combining ability:
• Specific combining ability effects are said to be more important than general combining ability
effects for characters like tuber yield and its components in potato.
• Hence, it is desirable to select the specific cross combinations based on their high specific
combining ability for the traits under consideration.
• For this, crosses among the parents are made in a specific pattern as in general combining ability.

6. Progeny test:
• These tests can be applied from seedling stage to clonal generations.
• The superior crosses are selected at the earliest opportunity so that larger populations of the
identified crosses are raised to go for individual clone selection in the segregating
progenies.
• The overriding criterion is that progeny means in initial generations must adequately reflect
the subsequent performance of the clones when evaluated in advance generations.
• Selection of superior crosses based on progeny means in seedling and/or early clonal
generations have been found to be effective for a number of characters including resistance
to potato cyst nematodes, late blight in foliage and tubers, gangrene, powdery scab and even
for tuber yield components.

7. Hybridization:
• Hybridization relates to production of hybrid progeny following sexual mating of two
parents identified based on desirable attributes.
• Potato being tetraploid, heterozygous and vegetatively propagated crop, it offers a
unique privilege of fixation of generated genetic variability in hybrid progeny for
effecting selection.
8. Planting of parental lines:
• Promising parents identified based on tuber yield, tuber characters, keeping quality,
processing attributes and resistance to biotic and abiotic factors are planted in
hybridization block.

9. Initial clonal generations:
• A clone is a group of plants produced through asexual reproduction form a single plant.
• Each plant within clone has the same heterozygous genotype as the seedling from which it
originated.
• The phenotypic variation within clone is due to environment and the genotype x environmental
interactions.
• The genotypic effects are heritable and therefore, stable. Environment and interactions effects
are non-heritable and can-not be fixed. The selection for quantitative characters based on
observation on single plant is highly unreliable and misleading (Gopal, 1997).
• Clones with undesirable tuber colour, tuber shape, eye depth and tuber cracking may be rejected
from the seedling stage onward, as these characters have a high repeatability over generations.

MUTATION BREEDING:
• Mutation is a sudden, stable and heritable change which alters the genotype of an organism.
• Mutations cause variations which are not always useful but, in a few cases, they are of a great
advantage to the breeder.
• Mutations which occur naturally are called spontaneous mutations and those which are induced
artificially are called induced mutations.
• Spontaneous mutations occurring in somatic cells are called sports.
• They are useful in vegetatively propagated plants. In potato several varieties have resulted from
sports (Miller, 1954).
• Some of these are Russet Burbank (mutation of smooth Burbank); Cobbler (mutation of Early
Rose); Red Triumph (mutation of Triumph); Red Warba (mutation of Warba); Russet Sebago
(mutation of Sebago); Red Pontiac (mutation of Pontiac)

INNOVATIVE BREEDING APPROACHES:
1. Embryo culture:
• Powerful tool in plant breeding for rescuing plants from incompatible crosses.
• The in vitro culture of immature embryos in potato allows the rescue of plants
from distant crosses.
• This technique has a definite advantage in a vegetatively propagated crop like
potato, because further propagation of rescued hybrids/genotypes is possible
through tubers.
• It, therefore, facilitates use of diverse gene pool for potato improvement.
• Embryo rescue may be applied both in the first interspecific cross and/or in the
first backcross.

• By using embryo rescue techniques, Eijlander and Stiekema (1994) have been successful in
bridging the crossability gap between 6X S. nigrum and S. tuberosum cultivar Desiree.
• At the Central Potato Research Institute, Shimla, an embryo culture medium was developed
for growing both immature and mature embryos of potato (Upadhya and Chandra, 1977).
• Using this medium, plantlets were recovered from mature/immature embryos from various
inter and intra-specific crosses.
• A list of successful rescued incompatible crosses includes (S. microdontum x S. canascence)
x (S. ocharanthan x S. phureja), pH-345 x (S. verrucosum x S. phureja), V-93 x CP- 1406,
pH-265 x SS-1304, Kufri Chandramukhi x S. bulbocastanum, Kufri Jyoti x S. microdontum
ssp. gigantophyllum and pH/DV-47 x S. microdontum (Chandra and Naik, 1993).

2. Anther culture for haploid production:
• Although dihaploid potatoes (2n=2x=24) can be produced parthenogenetically from tetraploid
(2n=4x=48) Solanum tuberosum using S. phureja pollinator, the production of monohaploids
(2n=1x=12) from dihaploids is rather laborious (Cappadocia and Ramulu, 1998).
• The production of haploids in large numbers enables construction of homozygous pure lines after
diploidization.
• In contrast to conventional breeding method, which takes 6-8 years of selfing to obtain pure lines, anther
culture can reduce the time to 6 months.
• New combinations of characters, which cannot be detected until F₂ or F3 generations, can be selected in
F1, when plants are grown from androgenetic lines (Sopory and Bajaj, 1987).
• In addition, the haploid tissue provides a good source for induction of desirable mutants to achieve
parasexual hybridization in order to maintain the original ploidy.
• Potato dihaploids have been used for mutant selection viz., cell lines resistant to Phytopthora infestans.

• Wenzel et al. (1979) proposed the combination of haploidy, protoplast fusion and classical breeding steps for
combining several traits of potato in an analytical synthetic breeding scheme.
• In this scheme, the monohaploid ploidy level is reached via two successive haploidization steps, and from these
monohaploids, spontaneous or induced doubling can produce homozygous dihaploids.
• Superior heterozygous interdihaploids expressing good agronomic traits can be produced from homozygous
interdihaploids by intensive sexual recombination and selection.
• Finally, selected heterozygous interdihaploids can be combined by somatic fusion, thus combining several
characters and expressing maximum heterozygocity at the tetraploid level.
• In spite of tremendous opportunities offered by androgenetic haploidization scheme in potato improvement, the
technique of potato anther culture needs further improvement.
• Since androgenetic response depends on the genotype and its interaction with nutritional conditions in vitro, there is
a requirement of universal medium for optimum growth and regeneration of potato anthers.
• The androgenetic procedures have additional advantages for the production of dihaploid potatoes in view of recent
demonstration that Solanum phureja induced dihaploids are not always completely parthenogenetic in origin.

3. Somacional variation:
• Spontaneous genetic variation induced in cell and tissue cultures is known as “somaclonal variation".
• This may be due to endomitosis, polyploidy, aneuploidy, gene amplification, somatic crossing over,
transposons, sister chromatid exchange and cryptic changes associated with chromosomal rearrangement.
• In potato, somaclonal variation has been reported in plants regenerated from protoplasts, stem explants, leaf
disc and other somatic tissues.
• The somaclones exhibit differences in plant height, canopy traits, leaf size and shape, colour, texture, size and
yield of tubers, as well as resistance to various pathogens and pests.
• In maximum cases, the somaclonal variability in potato is frequently associated with abnormal ploidy levels,
aneuploidy and mixoploidy (Sree-Ramulu et al., 1983).
• To investigate somaclonal variation at the DNA level, total EcoRI or BamHI digests of potato DNA were used
for cloning in plasmids pJL34, pUR2 and PUR250 (Landsmann and Uhrig, 1986).
• It was observed that 30% inserted DNA was unique, 47 % was repetitive and 23 % was of plastid origin.

4. Somatic hybridization:
• Advances in protoplast fusion technology have made somatic hybridization
technique of more immediate value for potato breeding.
• Using chemical or electrical procedures, protoplasts from different donor plants
can be fused together and somatic hybrids regenerated from the fusion products.
• In particular, the combination of breeding at dihaploid level with somatic
hybridization offers new opportunities for introducing novel characters into
potato, and of synthesizing superior tetraploid potato clones.
• Both inter-generic fusions with other Solanaceae genera and intra-generic fusions
with other Solanum species were extensively carried out in potato.

5. Marker assisted selection (MAS) and gene pyramiding:
• Over one million seedlings are usually screened for developing a new
commercially successful potato cultivar.
• Use of molecular markers (isozymes and DNA markers) for indirect screening of
progeny at seedling stage or even at seed stage can increase efficiency of selection
process.
• In principle, DNA markers are in no way different from visible markers and
isozymes. To be useful as a genetic marker, a trait must meet two criteria (i) it
must differentiate between the parents and (ii) it must be precisely reproduced in
the progeny.

List of qualitative and quantitative traits in potato linked with molecular markers. These markers
can be used for marker assisted selection in breeding programme.
Phenotype Marker System Chromosomal Location Closest Markers
Qualitative traits
Vertical Resistance to
late blight (R1)
RFLP, AFLP Chromosome V AFLP1, AFLP2
Resistance to cust
nematode (Gro VI)
RFLP, SCAR Chromosome V
Quantitativetraits
Late blight resistance SCAR Chromosome V GP 179
Tuber dormancy RFLP QTLs in 9chromosomes

6. Genetic transformation:
• Because of relative ease of introducing foreign genes into potato genome using
Agrobaterium tumefaciens, the potato has long been a favourite crop amongst
genetic engineers.
• Several diseases, insect pests and abiotic stresses affect potato.
• Attempts have, therefore, been directed world over to developing transgenic
potatoes tolerant to these stresses.

7. Pest resistance:
• The most popular transgenic strategy to control virus (es) is through coat protein (CP)- mediated
resistance, an exploitation of the classical "cross protection" phenomenon.
• This is widely effective against PVX, PVY and PLRV. Resistance to viruses has been reported
in field trials of transgenic potato plants expressing the CP gene(s) of PVX, PVY, PVX+PVY
and potato leaf roll virus (PLRV).
• Using this strategy two potato varieties, viz. Russet Burbank NewLeaf® Y and Shepody New
Leaf Y have been developed by Monsanto Company, USA.
• These varieties possess combined resistance against Colorado potato beetle (cry 34 gene) and
PVY (CP-PVY gene).
• Resistance to plant virus can also be achieved by transferring a gene that produces defective
movement protein (MP).

• Fungal diseases pose the serious biotic threat to potato. Late blight caused by Phytophthora
infestans is the most dreaded fungal disease of potato.
• Most of these strategies utilize basic information obtained from the study of host's active
defence mechanism. The active defence of plants against fungal attack involves generation of
reactive oxygen species like hydrogen peroxide.
• Enhancement of in vitro H₂O₂ synthesis can, therefore, confer resistance to fungal attack.
• Transgenic potato plants expressing a glucose oxidase gene, originally cloned from Aspergillus
niger have been developed. Glucose oxidase converts glucose into gluconic acid and H2O2.
• These transgenic plants possessed resistance to late blight.
• Similarly, osmotin gene encoding a class of pathogenesis related protein (PR-5) has also been
transferred into commercial potato cultivars for improved resistance to P. infestans.

• Another strategy of inducing hypersensitive cell death in response to fungal attack
at the site of infection has also been employed successfully.
• Under this approach, a bacterial ribonuclease gene (barnase, which degrades
ribonucleic acid) and an inhibitor of barnase, barstar, were introduced into potato.
• The two genes are engineered in transgenic potato in such a way that the level of
barnase will exceed to that of barstar only in the close vicinity of infection sites
leading to cell death specifically in infected host tissues that restricts spread of the
disease.
• Solanum bulbocastanum, a wild species of potato growing in Mexico has shown
resistance against late blight for the last 6 decades.

• The most widely practiced strategy to impart resistance to insect pests involves the use of
insecticidal protein of soil bacterium Bacillus thuringiensis.
• The bacterium produces proteinaceous crystals outside its endospore at the time of sporulation.
• These crystals contain proteins that are highly toxic to a range of insects.
• The crystal protein, when ingested by susceptible insects gets dissolved in the alkaline
environment of insect gut.
• The proteolytic enzymes secreted inside the insect gut then cleave the native protein into an
active molecule, which specifically binds to a receptor protein present in the brush border
epithelial cells of the gut lining.
• The bound toxin then penetrates into the cell membrane creating channels through which
electrolytes leak out.
• The affected insect larva dies due to non-specific ion leakage and gut septicaemia.

Quality improvement-Carbohydrates:
• Transgenic potatoes have been developed through metabolic-manipulation of starch synthesis to
predominantly produce only one type of starch, either amylose or amylopectin.
• Depending on the industrial applications, both amylose-rich starch and amylopectin-rich starch are
required as binding materials.
Quality improvement-Reduction in cold induced sweetening:
• When potatoes are stored at low temperature, the starch in the tubers gets converted into sugars.
• The key enzyme involved in the conversion is invertase.
• Such cold induced sweetened tubers are not suitable for processing and are also not palatable as
vegetable.
• Post Transcriptional Gene Silencing (PTGS) strategy to inhibit invertase enzyme has been deployed at
CPRI to reduce cold induced sweetening in Indian commercial varieties of potato.

Quality improvement-Nutritional qualities:
• Transgenic plants of potato cultivars Russet Burbank and Atlantic have been produced that
express BN2S gene of Brazil nut.
• The expression of this gene was, however, eight fold lower in transgenic tubers in comparison to
leaves.
• Tuber expression of this gene is being improved by utilising tuber specific promoters such as
patatin.
• A synthetic gene, producing 80% essential amino acids, was constructed and named High
Essential Amino Acid Encoding (HEAAE) at the International Potato Center (CIP), Lima, Peru.
• This gene was transferred into two potato clones K-2 and K-7. Protein analysis of transgenic
plants showed that HEAAE protein comprise about 0.02-0.35% of the total plant protein with
about 1.1% increase in essential amino acids.

Pharmaceuticals:
• Attempts are also being made to produce novel carbohydrates like fructan and cyclodextrin that are
routinely used in food and pharmaceutical industries.
• Edible vaccines against diseases like cholera have been produced in transgenic potato and are under
clinical trials.
True Potato Seed (TPS): Breeders have long sought to increase potatoes by seed. The production of
potato from true potato seed has several advantages compared to tubers, including:
• production of virus free stocks as viruses are generally not transmitted by seed,
• reduce storage problems because refrigeration of true potato seed is not necessary,
• lower shipping costs for true potato seed,
• easier shipping of true potato seed because 100 g true potato seed will seed a hectare while 2000 kg of
seed tubers are needed to seed the same area,
• consumption of all tubers produced as none need to be saved for next year's seed crop.

• The objective of true potato seed is to have completely homogeneous progeny.
• This can best be accomplished by the use of 4x families from 4x × 2x crosses
where the 2x parent produces 2n gametes.
• It is important that both parents be adapted to the area where the homogeneous
progeny are going to be grown.
• Studies have shown that higher seedling vigor and tuber yields resulted from this
approach compared to progeny produced from 4x × 4x crosses or progeny
obtained from open pollinated seed.

Breeding for tolerance to high temperature and heat:
• Germination and growth are favored by warm temperatures, while tuberization is favored by cool
temperatures, preferably below 18ºC.
• Normally, there is a reduction in size of tubers with temperatures above 18 to 20ºC during the tuberization
period.
• Practically no tuberization takes place with temperatures above 29ºC.
• In most warmer climates where potato is produced, tuberization would be improved if cultivars tolerating
higher temperatures during tuber formation could be developed.
• Breeding materials may be screened for heat tolerance by testing for foliage resistance to high temperature
and tuberization during high temperatures.
• For example, if plants are kept in a controlled environment at 50ºC for 8 hours during the night for a period of
14 days, susceptible plants will deteriorate significantly within 3 days.
• Clones are tested for tuberization by growing in a greenhouse at 30 to 38ºC during the tuberization period and
then comparing the amount of tuber formation.

Breeding for frost resistance:
• Screening for frost resistance is conducted in controlled environment chambers at freezing temperatures
and in the field in areas where frost occurs.
• A detached leaf technique may be used for quick and largescale screening for frost resistance.
• With this technique, leaves of the potato are exposed to temperatures of around 5 ºC for 8 hours.
• Leaves from susceptible plants lose their turgidity and become discolored due to osmosis from the
chloroplasts, effects which can be visually observed immediately.
Breeding for drought resistance:
• Drought resistance is desirable when potato is grown in areas where there are no irrigation facilities or
where irrigation facilities are inadequate.
• Screening for drought resistance can be done either in the field or in pots under simulated drought
conditions.

ACHIEVEMENTS:
1. Clonal Selection:
• Kufri Red potato is a clonal selection from Darjeeling Red Round; it was developed
from a single disease-free plant.
• Similarly, Kufri Safed is a clonal selection from the potato variety Phulwa.
2. Hybridization:
• Some prominent potato varieties developed through hybridization are Kufri Alankar,
Kufri Ashoka, Kufri Pukhraj, Kufri Surya, Kufri Arun, Kufri Khyati, Kufri Bahar, Kufri
Sadabahari, etc. Kufri Jyoti is late blight resistant and Kufri Sheetman is frost resistant.
• Kufri Khyati produces white oval tubers with shallow eyes, is moderately resistant to
late blight, and is suitable for cultivation in plains of India.

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