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V. Triticale Improvement at CIMMYT

V. Triticale Improvement at CIMMYT

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THE DEVELOPMENT OF TRITICALE



327



by utilizing three entirely different climatic zones at which the populations

were grown and selected. In the winter, the triticale nursery is grown at

Centro de Investigaciones Agricolas del Noroeste (CIANO), State of

Sonora, at 28O N latitude, 35 meters elevation. The summer nursery in

Mexico is grown in the Toluca Valley at 1 8 S 0 N latitude and 2600 meters

elevation. The University of Manitoba summer nursery is grown in the

Winnipeg area at 50° N and 230 meters elevation. Thus not only did the

program expand in area and number of workers involved, but the number

of generations grown per year doubled, the number of environments

tripled, and for the first time triticale breeding was introduced to tropical

regions requiring daylength insensitivity similar to that of the wheats which

are adapted to regions between 30° N and 30° S latitudes. The alternation

of generations between CIANO and Toluca permitted screening for strains

capable of performing well at two widely different environmental conditions. The disease infestations differed greatly at the two locations. This

has greatIy enhanced the possibilities of obtaining selections having wider

adaptation. A further advantage was gained by having access to large, diversified material in aggressive durum and bread wheat programs to which

triticale crosses could be made and from which new primary triticales could

be produced.

B.



BREEDING

PROGRAM



Preliminary work on triticale was started in 1963, when some triticale

strains were included among wheat populations obtained from Dr. J. A.

Rupert in Chile. Ingenieros Ricardo Rodriguez and Marco Quiiiones because of scientific curiosity made a number of crosses between these triticales and several Mexican dwarf wheats (Quiiiones, 1967). The triticale

lines originated from the University of Manitoba. The hybrids and selected

plants were brought to the Toluca nursery (State of Mexico) for observation. The need to overcome daylength sensitivity, reduce plant height, and

improve resistance to stripe rust became apparent immediately. Some degree of daylength insensitivity was recovered from crosses between triticales, but this was insufficient for crop production in Mexico. Improved

daylength insensitivity and disease resistance, were recovered in later generations from triticale X bread wheat crosses made at this time.

By 1967, a number of strains with enough resistance to disease, and

insensitivity to daylength had been developed to be included in replicated

yield tests. Results from tests at CIANO and Toluca indicated that the

triticale strains produced about one half as much grain as the best wheat

cultivars under similar conditions. The triticale strains were tall, late maturing, and at least as vigorous in the production of total plant material as

the best wheat cultivars. The depressed grain yields were attributed to the

high incidence of sterility and severe endosperm shriveling.



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F. J. ZILLINSKY



1. Improving Fertility

In 1968 a very intensive selection effort was devoted to finding plants

having better fertility. A few plants with improved fertility were found in

an F, population of a cross between two hexaploid triticales. The average

percentage of seed set of two of the original lines was about 6 % below

that of adapted bread wheat strains, and 15% above the best original hexaploid triticales. These few plants eventually provided a major contribution

to triticale improvement. Among the characters associated with these selections, which were later identified as Armadillo strains (Zillinsky and Borlaug, 1971), were high fertility, improved test weight, better grain yield,

insensitivity to daylength, one gene for dwarfness, early maturity, and good

nutritional quality. Each of the factors were found to be heritable and could

be easily transmitted to its progeny. Furthermore the Armadillo strains

were generally more cross compatible with bread wheat, durum wheat,

and rye than were the normal hexaploid strains in the program. This improved compatibility might be attributed to a higher proportion of viable

pollen when used as the pollen parent in crosses. A similar improvement

in the production of F, hybrids was observed when the strains were used

as the female parent.

Investigations on the origin of the unusual characteristics of the Armadillo strains (Fig. 4) revealed that the majority of the characteristics, such

as dwarfing, disease resistance, earliness, erect juvenile growth habit, short

spike, and smaller plumper kernels, must have been introduced from a

Mexican bread wheat having a NORIN 10 dwarfing gene. The bread wheat

is believed to have been introduced via spontaneous outcrossing on the

F, hybrid of cross X308, since the original cross, X308, from which the

Armadillo strains were selected, combined secondary hexaploid triticale

parents having no bread wheat in the progenitors. The outcrossed hybrid

was subsequently pollinated with hexaploid triticale pollen from neighboring plants in the triticale nursery. A verification that a bread wheat progenitor was involved in the origin of Armadillo was obtained in 1973 when

a D chromosome was found to be substituted for one of the rye chromosomes (Gustafson and Zillinsky, 1973; Gregory, 1973; Merker, 1973b).

Although the rye genome in Armadillo appears to have lost one pair

of chromosomes by a substitution, the total genotype was considerably improved by the modification. Whether this was due to the deletion of that

particular rye chromosome or to the favorable effects of the D genome chromosome has not yet been determined.

The Armadillo strains were used frequently as parents in crosses to other

hexaploid triticales both primary and secondary forms, to bread and durum

wheats, and to primary octoploid triticales during the following generations.



THE DEVELOPMENT OF TRITICALE



329



FIG.4. The plant type of the fertile selection Armadillo.



Selections with fertility approaching that of the Armadillo parent were obtained among the segregating populations. By 1970 practically all the material in the CIMMYT triticale program originated from crosses having Armadillo as a progenitor.

2. Lodging



Susceptibility to lodging was a common problem encountered by many

of the early investigators, including Muntzing, Kiss, and Sfinchez-Monge.

The problem was intensified under Mexican conditions owing to the tendency of long day-sensitive material to grow taller under short-day conditions. Even the single factor for dwarfing possessed by the Armadillo

strains was not sufficient to prevent lodging since the increase in fertility

and grain density increased the weight of the mature spike (Fig. 5 ) .

Attempts to improve lodging resistance included increasing straw thickness and incorporating more dwarfing genes from wheat. New primary

amphiploids, both hexaploid and octoploid, were produced using dwarf

durum and bread wheats. These were used as parents in crosses to



330



F. J. ZILLINSKY



FIG.5. Dwarfing in triticale: differences in plant height.



hexaploid triticale. Early attempts to incorporate more dwarfing genes

from bread and durum wheats having NORIN 10 dwarfing were discouraging. It was very difficult to maintain fertility among the dwarf selections.

The grain quality tended to deteriorate conspicuously. Similar problems

were encountered in the early stage of the wheat breeding program in

Mexico when NORIN 10 was used as a dwarfing source. Borlaug 1968;

Zillinsky and Borlaug, 1971 ) pointed out that only semidwarfs (singlegene dwarfs) with good fertility and acceptable grain type could be

isolated from crosses between NORIN 10 X tall wheats. All double dwarf

segregates were highly sterile and possessed very shriveled grain. Subsequent

recrossing and selection for fertility and grain plumpness resulted in the development of excellent double dwarfs, such as SONOM 64, INIA 66, possessing complete fertility and excellent grain type. Kiss (1968) reported

similar difficulty with sterility and grain shriveling when using the NORIN

wheat dwarfing sources. He subsequently used TOM THUMB with more

success.

Crosses between Armadillo strains and stiff-strawed, normal-height triticales resulted in only moderate improvements in lodging resistance. It

became obvious that if grain yields competitive with the Mexican dwarf

wheat were to be achieved, the straw length of triticale had to be reduced.

Since all the triticale germplasm possessed genomes of tall ryes, a major

obstacle to expression of the dwarfing characteristic in triticale was the



THE DEVELOPMENT OF TRITICALE



33 1



tall genotype of rye. An obvious solution was to replace these with genes

from dwarf ryes. A search for dwarf ryes among collections of spring ryes

resulted in the discovery of a single heterozygous dwarf plant in a rye population received from Dr. Darrell Morey of The Coastal Plains Experiment

Station, Tifton, Georgia (Zillinsky and Borlaug 1971 ) . The dwarf segregates among the progeny of this plant were identified as “Snoopy” selections. Unfortunately the original plant was susceptible to several diseases

(stripe rust, bacterial stripe, and scab) and had some other unfavorable

agronomic characteristics. It was necessary to improve the phenotype by

crossing to selected tall strains before crossing to triticale. Dwarf segregates

from crosses between Armadillo x Snoopy rye had sterility and seed

shriveling problems similar to those from the Armadillo X dwarf wheat.

Two-gene dwarf hexaploids were eventually obtained in 1972 which

were equal in fertility to Armadillo (Zillinsky and Lopez, 1973). These

originated from two sources: (a) hexaploid triticale x bread wheat, and

(b) octoploid triticale x hexaploid triticale. The F, hybrids from both

sources were equal to the triticale parent in height. The hybrids having

a bread wheat parent were much more sterile than those from octoploid x hexaploid crosses. It was necessary to overcome the sterility by

growing the F, plants in rows alternating with normal fertile hexaploid

triticale as a source of viable pollen for two generations.

3. Diseases



Triticale was first released for commercial production in Hungary in

1968. Even today only a few countries are growing limited acreages commercially. Information on diseases is rather scarce. Wherever the crop is

grown, disease symptoms appear, apparently caused by plant pathogens

which parasitize wheat and rye species. They have not been reported as a

serious limiting factor in triticale development. Fuentes ( 1973) summarized

the literature on diseases of triticale. Larter el al. (1968) reported that in

higher latitudes ergot caused by Claviceps purpurea is a serious problem.

Grain contaminated with sclerotia of ergot causes toxicity problems in

animal feed. There is very little genetic resistance to the disease, although

considerable protection from infection can be obtained among highly selffertile strains. This form of protection is present among cultivars of wheat

and other cereals.

European investigators have reported that triticale generally is more resistant to diseases than wheat (Pissarev, 1963; Shulyndin, 1972; Kiss, 1973).

Leaf rust (Puccinia recondita) and stem rust ( P . graminis) attack triticale

and are considered the most serious diseases at many of the international

triticale yield nurseries.

Leaf rust and stripe rust ( P . glumarum) are serious pathogens of triticale



332



F. J. ZILLINSKY



in Mexico, and natural infestations occur regularly in the summer nurseries

in the State of Mexico. Rajaram et ul. (1972) observed that the many of

the triticale strains in the CIMMYT program were susceptible in the seedling stage to 4 races of leaf rust which attack INIA, and SIETE CERROS and

other cultivars or bread wheat. However, some of these (19 out of 75)

were resistant in the adult plant stage. During investigation of patterns of

leaf rust development in triticale, it was observed that some strains which

are susceptible to leaf rust in the seedling and early adult stage abruptly

produce the telial stage prior to maturation (Zillinsky, 1973). This would

tend to restrict the production of inoculum and thus provide some degree of

protection. Quiiiones et ul. (1972) reported that each of the strains 6A-190,

ROSNER, Armadillo, BRONCO, and TOLUCA 16a have a single dominant gene

for resistance to leaf rust which was derived from the wheat parent, and

that resistance carried by the rye parent was not expressed in the amphiploid. This is probably true for seedling resistance, but adult plant resistance

is carried by octoploid triticale strains derived from cross between INIA

wheat and several ryes to races that attack INIA in both seedling and adult

stages (Rajaram et ul., 1972).

Resistance to stripe rust was essential to maintain a nursery in Toluca,

where stripe rust infestations can be devastating. Quiiiones and Rodriguez

(1973) observed almost 100% of the triticale strains were destroyed by

stripe rust in the first season the triticale nursery was grown at Toluca.

Resistance was obtained from intercrosses among resistant plants and backcrosses to resistant wheats. The continued use of resistant strains as parents

and heavy selection pressure for resistance has resulted in a degree of

resistance superior to that found in most durum and bread wheats to races

currently prevalent in Mexico.

Bacterial diseases attack triticale strains in the Mexico nurseries and

other areas of North America. Dr. Bradbury of the Commonwealth Mycological Institute, Kew, isolated Pseudomonus striufuciens from a bacterial

leaf stripe lesions on triticale from the Toluca nursery in 1972. During

the next growth cycle at CIANO in the Yaqui Valley, he isolated the bacterium Xanthornonus trunslucens from bacterial lesions on infected leaves

(J. M. Waller, private communication W-1549 and W-1557).

A very serious outbreak of bacterial stripe, probably due to Xanthornonus trunslucens, occurred on triticale in the nursery at Navojoa, Sonora,

in February and March 1970. Many of the strains were susceptible, and

they were almost completely defoliated. Resistant plants were selected and

used in crosses. The spread of the disease is highly dependent upon a favorable environment, which occurs occasionally in the nursery areas, and continuous dependable screening for resistance to the disease has not been

possible. In Mexico, rye strains have generally been more severely damaged

by bacterial diseases than the wheats.



THE DEVELOPMENT OF TRITICALE



333



Leaf blight caused by Fusarium nivale occurs regularly on triticale and

wheat in the Toluca nursery throughout the growing season. This fungus

is of little importance to spring crops in other regions of the world (Richardson et al., 1972), but it is devastating on susceptible strains of triticale

and wheat in the Toluca Valley. There does not appear to be clear cut

resistance among the triticale strains, although some strains are killed and

others damaged only slightly. The more tolerant strains are infected much

later in the growth cycle. This disease has not been observed at elevations

below 7000 feet in Mexico. It is possible that the disease is indigenous

on grass species in regions at high elevations in Mexico and other countries.

Fuentes ( 1973) has investigated leaf blotch on Septoria tritici wheat

and triticales in the CIMMYT breeding program. He has found that triticales are generally more resistant than wheats to the strains of this pathogen found in Mexico. He assumes that other areas, such as North Africa,

the Middle East, and South America, may have strains that are more

virulent, since some reports on the reaction of triticales to Septoria tritici

have indicated high susceptibility. Lesions of infected triticale leaves from

the nurseries in Mexico have been examined regularly since 1971. The

pycnidia of Septoria tritici have been isolated only rarely although pycnidia

resembling Septoria nordorum and Septoria avenue f. sp. triticea occur regularly. More intensive investigations need to be carried out on diseases causing leaf blotching, particularly in the cooler and more humid areas of the

tropics. It may be possible to replace wheat with triticale, which is more

resistant to these diseases.

Triticale appears to be more resistant to powdery mildew (Erisiphe

graminis) and the smuts (Ustilago spp.) than wheat. However D. D.

Morey observed powdery mildew on triticale in the winter nursery at

Tifton, Georgia. A few spikes infected with loose smut have been found

in the Toluca nursery. Occasional plants infected with downy mildew

(Sclerophthora macrospora) are found in the CIANO nursery each year.

Head blights, foot rots, and seed infections occur regularly in the summer

nurseries.

M. J. Richardson of East Craigs, Scotland, and J. M. Waller of the

C.M.I. Kew investigated diseases of triticale in the Mexico nurseries during

the fall of 1973. They observed fruiting structures of Ophiobolus graminis,

Cochliobolus sativus, and Fusarium graminearum on triticale plants. They

also isolated several seed-borne pathogens on seed produced in Toluca and

El Batan (Richardson and Waller, 1973).

Several virus diseases have appeared in triticale nurseries. The aphidtransmitted barley yellow dwarf virus infects triticale strains in the Mexico

nurseries. The proportion of plants infected is generally higher than among

wheats in the same area, but much less than either oats or barley. Symptoms on infected triticale plants are similar to those developed on infected



334



F. J. ZILLINSKY



bread wheats. Triticale plants infected with African cereal streak virus were

observed in nurseries at Njoro, Kenya, and Debre Zeit, Ethiopia, during

February and March 1973. Viruslike symptoms on the leaves of juvenile

triticale plants were observed in the nursery at Ankara, Turkey, in 1972,

but positive identification was not made.

Diseases have not generally appeared as a serious problem in the

CIMMYT triticale breeding program. However, as commercial production

increases, diseases that parasitize triticale will increase. A close watch on

disease development will have to be maintained as production spreads.

Genetic resistance appears to be available for most of the diseases observed

to date. It is extremely important that breeding programs maintain a broad

germplasm base to provide protection against present and future disease

infestations.

Dr. Alejandro Ortega, an entomologist in the CIMMYT corn program,

observed that triticale are generally attacked by the same insects as other

cereal crops. Infestations of corn leaf, English grain, and cereal root aphids

are common. Occasionally heavy infestations of shoot fly, frit fly, and stink

bugs have been observed on triticale in localized areas in Mexico. Triticale

plants infected with Hessian fly and root knot nematodes have been found

in North Africa. Care must be exercised in using insecticides on triticale.

Some strains of triticale are quite sensitive to pesticides applied as foliar

sprays.

4. Yield



The introduction of the Armadillo strains into replicated tests resulted

in a significant increase in grain yield. The degree of improvement was

influenced by soil fertility, diseases, and other environmental factors. The

Armadillo strains approached the Mexican bread wheats in grain yields

at low to moderate levels of nitrogen, but dropped off sharply with increases in levels of nitrogen. The Armadillo strains were less responsive

to nitrogen fertilization and more susceptible to lodging than the Mexican

dwarf bread wheats.

An estimate of the rate of improvement in grain yield of triticales compared to that of bread wheats in Mexico during the past 6 years can be

obtained from yield data from replicated tests at CIANO Experiment Station, Sonora (Fig. 6 ) . The rapid increase in yield improvement of triticale

between 1967 and 1969 was due to the introduction of Armadillo strains.

Improvement in yield during the next 2 years (1969-1970, 1971-1972)

occurred at more or less the same rate in both wheat and triticale. The

introduction of fertile two-gene dwarf triticales into the 1972-1 973 yield

tests resulted in a second significant increase in the rate of yield improvement. It is expected that as more dwarf triticale strains from the breeding



THE DEVELOPMENT OF TRITICALE



335



FIG.6. Yields of triticale at the Sonora, Mexico, winter nurseries. Comparison of

yields of top wheat vs the average of the top triticale strains.



program are advanced to the replicated trials, triticale yields will equal

or surpass those of the best bread wheats in the Yaqui Valley of Sonora.

Grain yields of triticale are already competitive with wheat in some of the

high mountain valleys and on some sandy soils areas of Mexico.

Further increments in grain yield in triticales are expected with the introduction of more dwarfing genes and improvements in tillering capacity,

grain density, plant structure. An immediate increase of 10-1 5 % could

be achieved if triticales could produce grain of equal density to wheat.

Increasing spike length may also result in yield increases perhaps compensating for the present deficiencies in tillering capacity.

5. Grain Quality

The most important unsolved problem in triticale breeding is abnormal

endosperm formation resulting in seed shriveling, low test weight, and low

germination rate. As the spikes approach maturity, abnormalities appear

and seed development becomes progressively more abnormal as it ripens.

The ripe seeds have a wrinkled seed coat, lack luster, and have a deep

crease. The endosperm is chalky in contrast to the hard vitreous seed of

durum and bread wheat. The test weights range from 58 to 72 kg/ha,

while the best bread wheats have test weights in excess of 80 kg/ha.



336



F. J. ZILLINSKY



Lebedeff (1934) and others have suggested that abnormal seed development may be due to the deleterious effect of inbreeding on the rye genome.

Sinchez-Monge (1969) showed that improvement in fertility and grain

quality could be achieved by using self-fertile ryes as parents in triticale

breeding. Inbred ryes are being used as parents in the CIMMYT program

although no naturally self-pollinating ryes are available.

More intensive research has recently been undertaken at the University

of Manitoba in an effort to identify the causes of seed shriveling and the

means to overcome the problem. Larter (1973) reported that research was

being conducted on cytogenetics and cytology (by Darvey and Kaltsikes) ,

histology (by Shealy) , and biochemistry (by Hill). This research has provided information on the physical and developmental aspects of seed

shriveling.

Bennett (1973) suggested that differences in the duration of the meiotic

cycle might influence endosperm development. Distinctive chromatin formation in the chromosomes of the rye genome may require more time for

replication than for the wheat chromosomes. Thus, disturbances in cell

reproduction in endosperm tissue result from segments of late-replicating

heterochromatin at the telomeres of rye chromosomes.

Improvements in grain quality have been achieved by breeding, although

progress is slow. Triticale is more sensitive to environmental influence than

wheat. A higher protein content tends to be associated with increased endosperm shriveling. Thus, the higher protein content of the grain observed

in the earlier triticale strains is deceiving and may be the result of abnormal

development at the expense of other nutrients.

Villegas (1973) has shown that a marked decrease in protein content

has occurred with improvement in yield capacity and kernel plumpness.

The increase in yield has more than compensated for the loss in protein

so that the production of protein per unit area has increased (Figs. 7 and

8).

Visual screening for plumper seed had to be applied with considerable caution. There is a strong tendency to eliminate all selections from

wide crosses possessing dwarfing genes, since these forms produce shriveled seeds. Improvement in seed type is obtained at the expense of

desired plant types or those having wide genetic diversity unless care is

exercised to avoid discarding those selected for characters other than plump

seed.

Dr. Ake Gustaffson of Lund, Sweden, initiated mutation research to improve seed quality in triticale in 1969, using mutagenic chemicals and radiation at several concentrations. Some improvement in seed type was obtained from this material among selections made in Mexico on the third

and fourth generations after treatment.



337



THE DEVELOPMENT OF TRITICALE



FIG.7. Comparison of triticale seed produced at CIANO, Sonora, in 1967, 1970,

and 1973.



0-



- 20



9-



- 18



8-



- 16



7-



-



6-



- I 2



-



c



- 10



-&



-



a



0



I



..



5-



VI

f=



0



-



-



14



-



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4-



- 8



3-



- 6



-



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a,



8



-



2-



4



-



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-



-



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FIG.8. Grain yield (0-0) vs percent protein ( O - - - O )in triticales at

CIMMYT, 1967-1973.



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