Vinod K K (2003) Breeding for biotic stress in plantation crops. In: Proceedings of the training programme on “Breeding for Biotic Stresses in Crop Plants", Tamil Nadu Agricultural
University, Coimbatore, India. Downloaded from http://kkvinod.webs.com. pp. 431-440.
This article may be cited as,
45
BREEDING FOR BIOTIC STRESS IN PLANTATION CROPS
K.K.Vinod
Rubber Research Institute of India, Kottayam 686 009
Introduction
Plantation crops are perennial crops, which are grown in larger areas and are
commercially important. They produce a wide range of produces from spices,
condiments, beverages, oil, industrial raw materials, medicines, fruits and other allied
materials. These crops are also known as cash crops or commodity crops. However,
the use of the term plantation crops is restricted to a few crops viz., coffee, tea,
rubber, coconut, cocoa, cardamom, oil palm etc. Among these crops coffee, tea,
rubber and coconut contribute much to the country’s exchequer.
Like any other crops cultivated under domesticated environment, these crops
are also affected by various pests and diseases. These biotic factors inflict a vide
range of detriments to the cause of their cultivation. Of these, fortunately very few
are known to cause serious concerns in the industry. Among them, some are of
historical importance, like coffee rust caused by Hemileia vastatrix, which caused the
catastrophic closure of coffee plantation industry in Ceylon during second half of 19th
century paving way to the development of tea industry and the South American leaf
blight (SALB) caused by Microcyclus ulei in rubber, which caused the shifting of
rubber cultivation to South and Southeast Asia including India, in the late 19th century
from native Brazil.
Being the crops of perennial nature, no focused attempt for breeding against
stress factors are practiced in any of these crops. However, the approach is to
integrate the breeding efforts combining all desirable attributes, including yield,
quality and resistance. Being major plantation crops of India, the present discussion
is confined to coffee, tea, rubber and coconut, though the principles involved remain
similar for any other plantation crop as well.
Plantation crops differ from annual field crops for perennial nature, size of the
individual plants and are often vegetatively propagated.
These crops are
predominantly cross pollinated and produce heterozygous and heterogeneous
population. Very limited genetic variability exists in their cultivated germplasm.
Although the breeding principles are identical, conventional breeding procedures
become highly impractical in plantation crops when the process got to involve many
generations, both in terms of enormous time and large volume of individuals to be
handled during the process. However, there is a great advantage with these crops
that at any time during the breeding process, emergence of any superior individual
can be fixed by vegetative multiplication or cloning. In crops of relatively recent origin
like tea, coffee and rubber the cultivars share a lot of similarity to their wild
progenitors and much time can be saved by screening existing populations, either
wild or cultivated for promising individuals.
Most of the biotic stresses are seasonal in nature. Field crops, which are also
seasonal comes under the threat of a stress when the periods of crop and the stress
coincide with each other. Whereas a perennial crop is of non-seasonal in nature and
are subjected to all kinds of biotic stress irrespective of the seasons. Therefore,
these crops undergo a sort of natural selection in situ against any adverse factors,
years after, and only the fittest is carried forward to future generations. However,
there would be a great deal of geographic variation in the stresses, as well as in the
Presented in the CAStraining on “Breeding for Biotic Stresses in Crop Plants” at Centre for Plant
BreedingandGenetics,TNAUorganisedfromFebruary3–23,2003
reaction of crops to different kinds of stress. In practice, most of the biotic factors are
controlled in most of the crops this way, but the fact only become apparent when
varieties are tested in different environments or a ‘new’ disease arrives.
Selection is the most important breeding strategy utilised in breeding
plantation crops. The concept of utilising vertical resistance (VR) in breeding for
biotic stress in annual and seasonal crops had been very useful, occasional disasters
notwithstanding. However, in plantation crops, long lived perennials growing in a
nearly non-seasonal environment, the effective use of VR is inconceivable and it
must be judged to have totally failed. Because any attempt to use VR in plantation
crops had resulted only in transient, non-durable resistance. The experience show
that pyramiding of VR only helped in delaying in the development of new pathotypes
a little. Further, the derivation of VR genes from wild species means that the breeder
would have to start from a very low genetic level in respect of other characters;
several backcrosses and many decades of efforts must be implied.
Nevertheless, the use of horizontal resistance (HR) in these crops is
promising as HR is fairly heritable in almost all the crops. The parents produce
slightly more resistant offspring. In many instances, directed selection for resistance
alone is not done and instead, judicious selection is done at a particular location on
the whole. In this process of selection, unhealthy and susceptible genotypes are
generally discarded; thereby breeders were unknowingly selecting the more resistant
clones, in other words accumulating HR.
Coffee (Coffea sp.)
Coffee is an important beverage crop belonging to the family Rubiaceae.
Cultivated coffee is derived mainly from two species, Coffea arabica (arabica coffee)
and C. canephora (robusta coffee). Another species C. liberica is produced and
traded in limited scale. C. arabica is a tetraploid (2n=44) having two botanical
varieties C. arabica var. arabica and C. arabica var. bourbon and is of Ethiopian
origin. C. canephora is diploid (2n=22) and has two types C. canephora var.
canephora and C. canephora var. nganda (Haarer, 1962) and is originated from
Congo river basins upto 1500 m altitude. C. liberica belong to west coast of W.
Africa (Willson, 1999).
Biotic factors
Coffee is affected by many diseases, viz., leaf rust or orange rust (Hemileia
vastatrix Berk and Br.), brown eye spot (Cercospora coffeicola), Coffee berry disease
(CBD) (Colletotrichum kahawae), South American leaf spot (Mycena citricola), pink
disease (Corticium salmonicolor), bacterial blight (Pseudomonas syringae), collar rot
(Fusarium stilboides), Armillaria root rot (Armillaria mellea) and many other minor
diseases. Insects which commonly cause damage in coffee are leaf minors
(Leucoptera meyricki, L. cofeella), giant looper (Ascotis selenaria reciprocara), scale
insects (Coccus sp.- green scale, Saissetia coffeae – brown scale, Ceroplastus
brevicauda – white waxy scale, Asterolecanium coffeae – star scale), mites
(Hemitarsonemus latus – yellow tea mite, Oligonichus coffeae – red spider mite),
yellow headed borer (Dirphya nigricornis), coffee berry borer (Hypothenemus
hampei), berry moth (Prophantis smaragdina) and few others.
Breeding for resistance
In coffee, all the early plantings come from a narrow genetic base. Earliest
approach for breeding for resistance for coffee rust was started in South India after it
432
was found that most of the cultivars of the arabica type are susceptible to this
disease. However, on the contrary, the resistance existed in most of the cultivars of
type robusta and some were even resistant to CBD. Hibrido de Timor, a natural
hybrid between C. arabica and C. canephora was found to be resistant to rust as well
as CBD. Table 45.1 shows the sources of resistance for breeding for various stress
factors in coffee.
A generalised scheme of breeding coffee is provided in Fig 45.1.
Improvement of C. arabica can be subdivided into several stages of which first is the
selection and testing of superior trees. Testing can identify superior individuals which
are then propagated by seeds. Two cycles of selfing is done before testing to
stabilise the characters in each line. Also the superior varieties can be crossed with
another, in double or multiple crossings, and further the improved individuals can be
selected from progenies. Back crossing may produce more superior varieties. Trees
so produced may be cloned for further multiplication as they may not breed true. The
best selections can be released for commercial cultivation. In vitro propagation
techniques by nodal cultures (Dublin, 1980) may help in speedy vegetative
propagation.
COLLECTION
C. canephora
Doubling of
chromosomes
Crossed
Crossing
‘Arabusta’
hybrids
Crosses with
compatible
types
Selection of
hybrids
Parents chosen,
selfed for 2
cycles
C. arabica
Second
cycle
Families
select
Hybrids
discard
Clones,
select,
trialled,
reselect
Clones used
per se
Clones as
parents of
seedlings
Fig 1. Scheme of coffee breeding
433
Cross
assessed
Families
discard
Clones
discard
Cultivation
Screening of wild and cultivated lines of Ethiopian coffee has been described
by Robinson (1976). Some two to three million coffee trees in planters’ crop were
screened to identify 650 resistant individuals to coffee berry disease (CBD) incited by
Colletotrichum kahawae. The first harvest of each tree was kept for seed and during
the three years required for progenies to come to bearing, each progeny was
repeatedly tested for resistance, yield and quality. This crash programme resulted in
production of some 50 to 100 new cultivars with a balanced domestication, each
consisting of upto 1000 trees bearing seed, and in only seven years.
The dwarf variety ‘Catimor’ is resistant to coffee rust. It has been developed
from Hibrido de Timor and is now being planted in many regions. van Boxtel (1994)
studied genetic transformation of coffee, using electroporation and biolistics to insert
genes that impart resistance to diseases and pests.
The robusta coffee, C. canephora is self incompatible. Wide variability exists
in this species as its geographical range of natural variation is very broad. Crossing
can be done between compatible populations and selections can be propagated
clonally.
Table 45.1. Cultivars used in coffee breeding (van der Vossen, 1985)
Name of the cultivar
Origin
BA
India
Blue mountain
Hibrido de Timor
Jamaica
Timor
K7
Kenya
Padang
Pretoria
Guatemala
Guatemala
Ruma Sudan
Sudan
S 288
S 333
S 795
India
Main characteristics
Believed to be natural hybrid of C. arabica and
C. liberica. Resistant to most races of leaf rust.
Some resistance to CBD.
Natural hybrid of C. arabica and C. canephora.
Resistant to CBD and most leaf rust.
Selected from Kents type from India. Some
resistance to leaf rust and CBD.
High yielding, partially resistant to CBD
Large leaves, tall, vigorous, very resistant to
CBD
Small low yielding, valuable source of resistance
to CBD
Believed to be natural hybrids of C. arabica and
C. liberica. Resistant to most races of leaf rust.
Crossing between C. arabica and C. canephora is also attempted for
transferring resistance from the latter to the former. However, the F1 progenies are
triploid and sterile. To circumvent this problem, C. canephora genome is doubled
using colchiploidy and the tetraploids developed are employed in hybridisation
(Capot, 1972). The hybrids are found to be intermediate between arabica and
robusta but rather close to robusta characteristics with less caffeine content and
superior quality. Hybrids are called ‘arabusta’ and show resistance to coffee rust.
Rubber (Hevea brasiliensis Muell. Arg.)
Para rubber, Hevea brasiliensis is a principle source of natural rubber
belonging to the family Euphorbiaceae. H. brasiliensis (2n = 36) is a monoecious
perennial tree which are highly cross pollinated. The genus Hevea consists of ten
species, of which H. brasileinsis is the only commercially exploited source of natural
rubber. The other related species are H. benthamiana, H. camargoana, H.
camporum, H. guianensis, H. microphylla, H. nitida, H. passiflora, H. rigidifolia and H.
434
spruceana. Almost all the species are intercrossable. The crop has its origin from
Amazon basin in Brazil.
Biotic factors
The rubber tree is infected by many diseases viz., South American leaf blight
(Microcyclus ulei), abnormal leaf fall disease (Phytophthora palmivora), powdery
mildew (Oidium heveae), Corynespora leaf fall disease (Corynespora cassiicola),
Gloeosporium leaf spot (Colletotrichum gloeosporoides), pink disease (Corticium
salmonicolor), thread blight (Pellicularia filamentosa), dry rot (Ustulina duesta),
mouldy rot (Ceratocystis fimbricata), brown root disease (Phellinus noxius), white
root disease (Rigidoporus lignosus) and few other minor diseases. No serious insect
are reported to damage the tree.
Breeding for resistance
The rubber tree is introduced into cultivation very recently. The genetic base
of the cultivated germplasm is very narrow, converging to a very few seeds collected
from upper Amazon basin near river Tapajos in Brazil. Though rubber tree is
infected by many diseases, the plantation industry suffers mainly from only one really
devastating pathogen causing South American leaf blight (SALB). This disease in
still confined to American sub-continent and all the rubber growing areas of South
and Southeast Asia are free from it. However, it is already proved that none of the
cultivated varieties in Asia are resistant to this disease when tested at various
locations of South America. However, in recent years, another disease Corynespora
leaf fall (CLF) has gained importance for wiping out entire RRIC 103 plantations of
Sri Lanka, which had almost gained its name SALB of Asia.
Clonal selection is the most important procedure followed in breeding rubber.
Clones can be evolved at any stages of different breeding steps. Usually selective
hybridisation of promising parents is done among themselves and also with wild
germplasm lines. The progenies are directly selected from seedling nurseries and
cloned for further evaluation. Also, natural seedling population or half-sib population
are also screened for desirable characters including resistance. Susceptible and
poor performing clones are generally discarded. Polycross gardens comprising of
pre-potent clones are also utilised and the selection is generally exercised in the
polyclonal seedling orchards, even at the stage of maturity. The selections are
directly carried forward for clonal evaluation and selection. A general scheme of
rubber improvement is provide din Fig 45.2.
Apart from H. brasiliensis, SALB affects only three more species of Hevea, H.
benthamiana, H. guianensis and H. spruceana (Langford, 1945; Chee and Holliday,
1986). Others species are free from infection. Eleven physiological races are
reported to be identified for this disease. Though H. brasiliensis is totally affected by
this disease immune reactions are shown by some H. benthamiana, H. spruceana
and H. pauciflora derivatives. Sporadic attempts to use these immunities, by
crossing with H. brasiliensis had produced clones with transient and non-durable
resistance (Simmonds, 1989).
The expedition conducted by the International Rubber Research and
Development Board (IRRDB) in 1981 to three districts of Acre, Rondonia and Mato
Grosso of Brazil, for induction of more wild genotypes for widening genetic variability,
collected 194 high yielding trees which were not affected by Phytophthora and SALB
(Ong et al., 1983). Among these collections, continuous variation for SALB
resistance was found in field trials at French Guyana (Clement-Damage et al.,
435
1996). In India, variability for Phytophthora resistance was found more in Mato
Grosso provenances (Mercy et al., 1995).
Table 45.2. Clones showing sources of resistance in Hevea
Resistance
characteristics
Disease
Genotypes
Phytophthora leaf fall
RRII 105, PB 217, GT 1, Gl
1
LCB 870
PB 86, GT 1, Gl 1, PR 107,
PB 5/139, RRIM 703, RRII
208, PB 310
PB 217, PB 260, RRIM 600
PR 255, PR 261, PB 217,
RRIM 600
RRIM 600, GT 1
PB 217, PB 235, PB 260
PA 31, IAN 717, IAN 6486,
IAN 7388, IAN 7657, FX
25, FX 614, FX 636
PB 86, RRIM 513, Gl 1, PR
107, GT 1, PB 260
Powdery mildew
Gloeosporium leaf
spot
Corynespora leaf fall
South American leaf
blight
Pink disease
Mouldy rot
PB 5/51, GT 1
Reference
Moderate
resistance
Resistant
Shows
tolerance
Ramakrishnan &
Pillai, 1961
Tolerant
Soepadmo &
Pawirosoemardjo,
1977
Manju et al., 2001
Kamar & Hidir, 1996
Holliday, 1970
Pinheiro et al., 1982
Moderate
resistance
Varying
degrees of
resistance
Less
susceptible
Less
susceptible
Edathil et al., 2000
Ramakrrishnan &
Pillai, 1961
RRIM, 1992
Kothandaraman &
Idicula, 2000
Studies on genetic control of resistance to Gloeosporium leaf spot, powdery
mildew and Phytophthora had revealed that there are no signs of vertical resistance
existing. Since the diseases differ ecologically (Gloeosporium leaf disease is worse
in wet areas, Phytophthora leaf fall in drier more seasonal climates) an array of local
clones show different spectra of resistance (Wycherly, 1969). However, it is found
that the horizontal resistance in Hevea is fairly heritable. A list of cultivated clones
harbouring the sources for resistance to many diseases is given in table 45.2.
Few Brazilian clones introduced earlier from Brazil viz., IAN 873 and IAN 717
have comparatively good yielding and tolerance to Colletotrichum and some
physiological races of SALB (Ong et al., 1985). Identification of markers for Oidium
and Phytophthora resistance are being attempted using RAPD markers (Shoucai et
al., 1994; Jacob, 1996).
Tea ( Camellia sinensis (L.) O. Kuntze)
Tea, another important beverage crop belong to the family Theaceae, is
originated in Asia, centred around Himalayan mountains. The cultivated species,
Camellia sinensis (L) O. Kuntze, is a diploid (2n = 30). There are two major types of
tea, commonly known as Chinese tea and Assam tea. A less known third type
Cambod tea also exists. These are often referred to as Camellia sinensis, C.
assamica and C. assamica ssp. lasiocalyx respectively (Wight, 1962). The Chinese
and Assam types are also known as C. sinensis var. sinensis, C. sinensis var.
assamica. The heterogeneity of commercial population can be attributed to the
outbreeding nature of the tea plant; and natural hybridization for a prolonged period
between the three types and their allies, contributed to the evolution of the present
day commercial populations (Sharma and Venkataramani, 1974).
436
Biotic factors
The tea plants are infected by a host of pathogens and insect pests. The
important diseases are, blister blight (Exobasidium vexans), red rust (Cephaleuros
parasiticus), canker (Phomopsis theae), pink disease (Corticium salmonicolor), root
splitting disease (Armillaria mellea), charcoal stump rot (Ustulina duesta) and brown
root disease (Fomes noxius). Insect pests include mosquito bug (Helopeltis
theivora), South African citrus thrip (Scirtothrips aurantii), scarlet mite (Brevipalpus
phoenicis), carpenter moth (Teregra quadrangula), shot hole borer (Euwallacea
fornicatus), stem borer (Sahydrassis malabaricus), termites and also few other pests
like nematodes.
Breeding for resistance
Though there are a few biotic factors which are of serious concern to the tea
plantation industry, breeding for resistance to pests and diseases has not been a
criterion of great importance so far in tea selection. Relatively severe damage from
these factors which affect specific clones consistently during early stages of
multiplication would likely to lead discarding of these clones from further
advancement.
Even if there is any related species with a great degree of resistance to biotic
stress, those species which do not produce tea are usually left out from the breeding
programmes, since such crosses produce very inferior quality tea and are not
acceptable. Also since the available genetic base of the cultivated tea is so narrow
that scope for any further improvement for resistance within the available base is
very limited (Willson, 1999).
Coconut (Cocos nucifera L.)
The coconut palm (Cocos nucifera L.) (2n = 32) is one of the major perennial
oil crops of the tropics. Coconut belongs to family Palmae and the trees are cross
pollinated. The exact location of origin of Cocos nucifera is not known, as its wild
types are found spread widely. It is believed that the spread was from South
America ( van Sloten et al., 1993). There are broadly two types classified based on
stature – the talls and the dwarfs.
Biotic factors
Coconut is affected by few fungal pathogens causing diseases like, bud rot
(Phytophthora palmivora), stem bleeding (Thielaviopsis paradoxa), basal stem rot
(Ganoderma lucidum and G. applanatum) and grey leaf spot (Pestalotia palmarum).
Coconut root wilt is considered to be of very complex aetiology of many organisms.
The common pests affecting the palms are the rhinoceros beetle (Oryctes
rhinoceros) , Asian palm weevil (Rhynchophorus ferrugineus and R. vulneratus), leaf
eating caterpillar, (Opisina arenosella) and cockchafer beetle (Leucopholis
coneophora).
Breeding for resistance
Though into cultivation for a long period, genetic improvement in coconut has
been a very slow process, and at one time it was considered as neglected in terms of
breeding and genetics (Harries and de Pork, 1971; Williams et al., 1975). However,
declining coconut cultivation in the major producing areas due to various biotic
threats has restored the efforts for breeding for resistance in recent period. A list of
437
cultivars and hybrids those show some sort of resistance in coconut is furnished in
table 45.3.
Table 45.3. Few resistant coconut cultivars and hybrids showing tolerance to biotic
factors
Biotic factor
Burrowing
nematode,
Rhadopholus
similis
Tatipaka
disease,
Phytoplasma
Cultivars / hybrids
Kenthali, Klappawangi, Java Tall
Lakhdeep ordinary × Gangabondam
Chowghat orange dwarf × west coast
tall
Malayan dwarf yellow × Java giant
San Ramon × Gangabondam
Java giant × Malayan dwarf yellow
Gangabondam
Resistance
Reference
Tolerant
Koshy et al.,
1983
Tolerant
Rajamannar
et al., 1993
The widespread incidence of root wilt disease in Kerala, has caused a great
concern in the industry as disease could not be controlled by conventional plant
protection measures. It was felt that the development of resistant/tolerant genotypes
is the only practical solution to combat this disease, though it is a long term process.
However, in the varietal screening programme to evaluate the yield potential and
resistance/tolerance to root (wilt) disease, so far none of the cultivar/hybrid was
found to be tolerant. However D × T hybrids were found to perform better with regard
to the yield in the diseased area.
In the screening programme, a large number of palms that had withstood root
wilt in the ‘hot spot’ areas were screened and resistant palms identified. T × T, T × D,
D × T and D × D crosses and inter-se mating were effected among these selected
palms. Seedlings raised from such crosses were under-planted in 'hot spots' to
subject them to vigorous natural selection. Disease escapes were subjected to
serological test to ensure freedom from root(wilt) pathogen. Hybrids involving
disease-free Chowghat green dwarf (CGD) palms as female and west coast tall
(WCT) as male planted in 1991 have so far not taken up the disease. For breeding
purposes the selection of genetic material in crosses has to accommodate for the
genetic variability encountered in germplasm collections. With the advent of DNA
marker technology, the characterisation of genetic diversity in coconut germplasm at
the DNA level has only recently begun to substitute other strategies like isozyme or
leaf polyphenol analysis. The application of DNA marker-based selection in breeding
programmes is particularly useful for woody species with long vegetation cycles
when desired characters are expressed only after several years of growth. Through
QTL markers the corresponding genotypes can be detected already at the seedling
stage which results in an environment-independent, scientific basis for selection and
ultimately in cost reduction and shortening of breeding programmes.
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