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V. Evaluation of Wild and Primitive Forms of Wheat and Barley

V. Evaluation of Wild and Primitive Forms of Wheat and Barley

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germplasm available for evaluation, and the desirable traits revealed, and

whether repeated backcrossing is needed to eliminate undesirable traits

introduced from the wild or primitive parent. The evaluation of wild

relatives of crop plants, including wheat and barley, has also been reviewed by Harlan (1984).

Many regions in the world have succeeded in improving crop production

through the introduction of high-yielding varieties. However, these varieties have not met with great success in West Asia and North Africa because

of their intolerance to an environment where moisture is limited and inputs

are very low (Srivastava and Damania, 1989). To improve and stabilize

cereal production in the drylands, characters such as earliness plus tolerance to drought, temperature extremes, low plant nutrients, and diseases

need to be incorporated into varieties. The genes for these characters can

probably be found in wild relatives and primitive forms that are well

adapted to such environments through independent survival over a very

long period of time.

Wheat and barley plant breeders in developed countries consider landraces and primitive forms as unadapted germplasm and Hallauer and

Miranda (1981) termed as exotics all germplasm that does not have immediate use without selection for adaptation to a given area. The exploitation

of wild and primitive forms in wheat breeding has been insufficient for four

reasons. First, collections of wild progenitors in the past have been fragmentary as well as scanty and material available in collections is not

representative (Croston and Williams, 1981). Second, work on wild forms

has primarily concentrated on evolutionary (Feldman and Sears, 1981) and

taxonomic studies (Bowden, 1959; Chennaveeraiah, 1960; Morris and

Sears, 1967; Kimber and Feldman 1987). Third, wild relatives are not well

adapted to Europe and North America and hence are used mainly as

single-gene donors. Finally, variability between and within populations of

wild species has not been looked at in adequate detail and utilization has

hardly commenced (Srivastava et al., 1988).

The principal reason for utilizing wild species such as Aegilops, Agropyron, and Triticum dicoccoides Korn. in wheat breeding has been the

transfer of genes for disease resistance, salinity tolerance, and highprotein content, respectively, when these desirable traits are not found in

the available genetic stocks. However, confirmation of the sources of

resistance and cataloging of genes for resistance should precede any attempt at transfer from the wild to the cultivated forms. This would involve

collecting and evaluating in-depth relevant germplasm collections for genetic variability. In-depth evaluation would consist of replicated tests at

different locations, resulting in genetic analyses and observations on traits

such as disease resistance.



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It is also useful to gain knowledge of genetic relationships between the

wild donor and cultivated recipient species because without ready crossability, desirable traits cannot be easily transferred. Thus, wild progenitors

of the cultivated species should be considered an important source of

variability for broadening the genetic bases of cultivated crops (Harlan,

1976; Hawkes, 1977; Lange and Balkema-Boomstra, 1988). Brown (1978)

states that the genetic resources of wild relatives of crop plants should be

systematically evaluated, for these sources of genes will supplement, and

even rival, the primitive landraces in their effectiveness in crop improvement programs. There is an opinion among certain workers, especially

those involved in breeding for favorable environments, that the variability

in landraces of wheat and barley has been fully exploited and for further

progress in introducing useful genes one should turn to wild relatives and

other alien germplasm of the secondary and tertiary gene pools.

Strampelli, working in Italy, was among the first plant breeders in

Europe to utilize wild and primitive genetic resources, especially Triticum

villosum Schur. and T . spelta L., to improve wheat in 1906 (Maliani and

Bianchi, 1979). Elliot (1957) transferred stem rust resistance to common

wheat from Agropyron elogatum and Riley et al. (1968) transferred yellow

rust resistance from Aegilops comosa Sibth. to cultivated wheat by genetically induced homologous recombination.

One of the most detailed evaluation studies of morphological, physiological, genetic, and cytological characteristics of Aegilops and Triticum

species was carried out at the University of Kyoto (Kihara et al., 1965). A

geographical survey of species of wheat and its wild relative Aegilops was

conducted following the University of Kyoto expedition to Afghanistan,

Iran, and Pakistan in 1955. Emphasis was placed on collecting Aegilops

squarrosa L., the probable donor of the D genome to cultivated wheat;

other species were also sampled whenever possible. There was evidence

that bread wheat arose as a hybrid between cultivated emmer ( T . dicoccum

Schub.) and A . squurrosu. This study was not only illustrated with photographs, but also contained valuable information on utilization of the

germplasm. Cox et a/. (1989) evaluated 212 accessions of A. squarrosa

from the University of Kyoto collection using polyacrylarnide gel electrophoresis and found gliadin diversity to be higher than in the D genome of

cultivated bread wheat.

Genetic variability in Aegilops species and primitive forms of wheat has

been studied by several researchers (Hillel et al., 1973; Sharma et a/.,

1981; Dhaliwal et al., 1986; Waines et al., 1987), whereas in the past more

emphasis was placed on Triticum dicoccoides, the wild progenitor of

wheat (Lawrence et al., 1958; Avivi, 1979) as reviewed by Poyarkova

(1988). Also, Gerechter-Amitai and Stubbs (1970) found the source of

resistance to yellow rust in T. dicoccoides from Palestine.



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In another evaluation of primitive and wild types of wheat comprising 75

accessions of T . boeoticum Boiss., T . araraticum Jakubz., and T . dicoccoides; 42 of T . urartu Tuman.; and 34 of A . squarrosa seeking resistance to leaf rust, Hessian fly, and greenbug, Gill et al. (1989) found that all

species except T . dicoccoides had resistance to both leaf rust and Hessian

fly. Only A . squarrosa contained some resistance to greenbug, T . boeoticum had an intermediate response, but all other species were susceptible.

Multiple resistance lines to leaf rust and Hessian fly were identified, but

only A . squarrosa had two lines resistant to all three pests.

Hillel et al. (1973) evaluated A . longissima Schweinf. and A . speltoides

Tausch, two loosely related species that differ in their mating systems, to

assess the direct effect of the mating system on the amount of genetic

variability. They found that for most of the 36 quantitative characters

examined, the differences between populations, the total variances of the

populations, and the mean within-species variances were greater in the

selfer (longissima) than the outbreeder (speltoides). These differences

were attributed to the low probability of a successful gene flow in

A . longissima, with each isolated population adapted to a specific microenvironment.

Ninety-three accessions of cultivated emmer wheat ( T . dicoccum), five

each of two wild tetraploid wheats ( T . dicoccoides)and T . araraticum, and

the cultivated varieties ‘Modoc’ ( T . durum) and ‘Anza’ ( T . aestiuum) were

evaluated for plant height, seed weight, flour protein content, and flour

lysine content, as well as several morphological and grain quality characters by Sharma et al. (1981). Variability among lines for each trait in

different species was significant except plant height in dicoccoides and

araraticum. Primitive and wild wheats were higher in protein and lysine

content, but lower in spike weight and 1000-kernel weight than the two

modern cultivars. It seems that selection for larger kernels has resulted in a

drop in the protein content of seeds from the wild species to the modern

wheats. Lawrence et al. (1958) also found higher protein and lysine contents in wild wheats than in cultivated bread and durum wheats, but only

one accession of T . dicoccoides and T . monococcum L. were analyzed.

Avivi (1978) evaluated 47 samples of T . dicoccoides for protein content in

kernels and found it to be highly variable, ranging from 19% to 28%.

Waines (1983) did a comparative study of primitive diploid wheats such

as T . monococcum with modern polyploid varieties and advocated the

former’s direct usage as commercial varieties. Among the several positive

characteristics of diploid wheats mentioned were less extraneous genetic

material, only seven linkage groups and hence easier to manipulate than

polyploid wheats, greater ecogeographic distribution and hence wider

adaptability, and resistances to pests and diseases. However, Waines

(1983) did not fully evaluate grain quality aspects such as pasta and dough



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products, which are vital to the success of any wheat variety, although one

may tend to agree with him that exploratory research should be carried out

to see if diploid wheats have a future as commercial varieties.

Hordeum spontaneum C. Koch. is now recognized as the only progenitor of cultivated barley (Harlan, 1979). Wild barleys, H. spontaneum and

H . murinum, and cultivated varieties from Afghanistan were collected by

the Kyoto University Scientific Expedition. The morphological, physiological, and genetic characterization are described by Takahashi et al.

(1965). Resistance to barley powdery mildew was also found in H. spontaneum, but the reaction was classified as being different from that of the

cultivated forms. The overall diversity in this collection was reported to be

low and the wild forms were less variable than the cultivated. Jana et al.

(1987) studied genetic diversity in morphological characters in H. spontaneum and cultivated barleys from the Near East and also found that the

latter were more variable than the former. However, it must be considered

that this wild form in the near East has a long history of survival, has

undergone millenia of natural selection pressures and therefore is better

adapted to harsh environments (if not as variable as the cultivated landraces), and hence is a very valuable genetic resource for abiotic stress

tolerance genes (Grando et al., 1985).

An evaluation of H. spontaneum accessions was also carried out by

Ceccarelli and Grando (1987) to assess the amount of useful genetic variability within this species. The results indicated that the progenitor is a

useful source of genes for a number of economically important characters

for breeding barley in the dry areas. Bakhteyev (1979) evaluated a collection of 77 samples of the same wild species originating from Iran, Iraq, and

Turkey at an experimental farm in the Soviet Union. Considerable variability was observed in this study and the species merits breeders’ interest

especially for adaptation to dry areas.

Landraces of primitive wheats have been evaluated for several economically important traits. Blum et al. (1987) evaluated 13 accessions of

T. compactum Host., a form of wheat cultivated in Syria and Palestine in

the prepottery neolithic period (Renfrew, 1969), for grain quality. It was

found, while comparing these with some modern cultivars of bread and

durum wheat, that the latter were superior in all characters tested except

protein content and quality.

In a comparative study of wild and primitive forms of Triticum, Asins

and Carbonell (1986) provided information for future use on intraspecific

variability differences among species. Robertson et al. (1979) evaluated

the genetic variability in primitive wheats for seedling root numbers, as it is

well known that this character is probably responsible for drought resistance in wheats. Among the 16 species studied, the highest root numbers



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were found in T. durum and the lowest in T . araraticum; seed weight was

positively correlated with root number. A test of progenies showed that

this character was stable from one generation to the next over two environments. O’Toole and Bland (1987) have reviewed genotypic variation in

root systems of cultivated wheat and Aegilops.

Electrophoretic techniques also have been applied to the study of variability of storage proteins in wild and primitive forms of wheat (Cole er al.,

1981; Damania er al., 1988) and barley (Jana et al., 1987). Using this

technique, Nevo et al. (1979) showed that there was greater variability in

wild and weedy barleys ( H . sponraneum) collected from Palestine than in a

composite cross of cultivated barley that included more than 6000 varieties

in its parentage. This result was surprising since cultivated barley is conspicuously more variable than its wild and weedy relatives from the Near

East (Harlan, 1984). However, Jana and Pietrzak (1988) reported almost

identical levels of variability between the two in material collected from

Greece, Jordan, Syria, and Turkey.

Nevo et al. (1982, 1988) studied genetic diversity within and between

Turkish populations of wild emmer, T . dicoccoides, utilizing electrophoretic and statistical analysis, and reported that climatic selection

played an important role in genetic differentiation of populations of this

species and that the wild gene pool represents a significant genetic resource for utilization in wheat improvement. In another study of the same

material, Nevo and Payne (1987) reported variability in seed storage

protein and the use of certain high-molecular-weight glutenins for improvement of bread-making qualities of wheat.

Variability for kernel proteins in 841 accessions of T . dicoccoides has

been reported also by Mansur-Vergara et al. (1986) using gel electrophoresis. The protein content measured ranged from 15% to 25% with

some accessions having high protein content as well as large kernel size. A

high percentage of protein content was also reported by Srivastava and

Damania (1989) in dicoccoides accessions from Syria and by Avivi (1978)

in those from Palestine.

In a study of 167 accessions of T . dicoccum from 23 different countries

of origin using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Vallega and Waines (1987) identified a total of 20

alleles out of which 9 were different from those reported by earlier work.

The newly discovered alleles enhance the genetic variability available to

improve the industrial quality of wheats, and some of them may facilitate

basic research on the relationship of industrial quality with highmolecular-weight glutenin subunit number.

Success in future crop improvement depends largely on the ability to

exploit existing genetic resources in wild relative and primitive forms,



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especially for less favorable environments. A better utilization and exploitation of these resources requires greater understanding of critical issues

related to evolutionary pathways, geographical distribution, genetic diversity, and multicharacter associations. Variability studies, such as those

described earlier, have provided this vital information. However, much

more work needs to be done before evaluation can be instrumental in

greater use of genes from wild relatives and primitive forms.



VI. DOCUMENTATION OF GENETIC RESOURCES

An efficient system for dissemination of evaluation data on genetic

resources material held in genebanks is essential if it is to be of use to

breeders. Databases of genetic resources information on world collections

have been established and contain a formidable amount of evaluation

information that needs analysis and documentation (Ford-Lloyd, 1978).

For example, 12,129 accessions of barley from a world collection were

evaluated by ICARDA at one location (Somaroo et al. 1986, 1988); there

was significant variability among the landraces for such characters as days

to heading, plant height, 1000-grain weight, protein/lysine ratio, and resistance to diseases.

In recent years much effort has been devoted to making these databases

as comprehensive and mutually compatible as possible. However, less

effort is being channeled toward considering how the results of these

studies might be put to use. This is because most users are interested

primarily in a very restricted aspect of the data (Williams et af., 1980).

Plant breeders may be interested in an immediate problem such as resistance to a particular pathogen or a specific agronomic trait. Alternatively,

their interest may reflect locally prevailing environmental conditions. For

example, breeders at ICARDA are not interested in plants adapted for

favorable conditions, as such environments are not common in West Asia

and North Africa, where the Center operates (Damania and Srivastava,

1989). However, an international genetic resources center might be expected to take a wider view and Williams et al. (1980) contend that genetic

resources evaluation data presently stored in computer memory banks

contain more information of practical value than is immediately apparent

without proper analysis. A detailed study of network analysis of genetic

resources data has been attempted (Williams et af.,1980; Robinson et af.,

1980; Burt et al., 1980).

Internationally agreed descriptor states are not used when evaluation

data are exchanged between genetic resources workers. Considerable time



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and effort would be saved if a lengthy description of the method and

intervals used for recording each character is avoided. The IBPGR has

been convening small working groups of scientists for the purpose of

arriving at an internationally agreed upon list of descriptors for describing

information for wheat (IBPGR, 1985) and barley (IBPGR, 1982). However,

experience has shown that it is too time-consuming to record observations

on all descriptors mentioned in the descriptor lists, as the method of

recording and the selection of characters are very much dictated by the

region and the needs of local breeders at each institution concerned. It is

also necessary to set out data in a standard format using a generally agreed

upon series of descriptors and descriptor states for the crop. In this way

the data can be entered into computers, retrieved, and exchanged among

institutions with the least possible confusion and optimum efficiency

(Hawkes 1985).

For the purpose of utilization, systematic analysis and description of

samples is useful in both distinguishing between populations and identifying duplicates, as well as in providing information on the extent of

variation within a given germplasm collection. It is axiomatic that the more

documentation on a collection, the greater the chance of its rational utilization. Information from the site where a particular sample was collected

may be extremely important. For instance, at ICARDA, germplasm that is

described as having a short maturity period receives immediate attention

of the breeders as this trait is very useful to escape drought and high

temperatures during grain filling in the dry areas. Therefore, information

recorded by germplasm collectors at site would be very valuable later

when the samples are evaluated.

Peeters (1988) studied statistically a large barley germplasm collection

at Cambridge and reported that despite extensive collecting activity in

recent years and subsequent exchange between countries, combinations

of characters have remained substantially different in germplasm by country gene pool. Material from the United States now contains more variability in toto than material from any other country. Subsequently, Peeters

and Martinelli (1989) used hierarchical cluster analysis to classify entries

from this collection according to their degree of similarity and concluded

that this statistical analysis procedure could be used as a tool to classify

entries to their respective gene pools even when no passport data are

available.

Often those responsible for entering data recorded at a collecting site

into a computer data base believe that lengthy descriptive notes made at

the collection site, for example, notes on disease observations or peculiarities of the habitat, are not relevant and hence should be omitted. Nothing

could be more erroneous. Although it is recommended that passport data



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V. Evaluation of Wild and Primitive Forms of Wheat and Barley

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