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International Maize and Wheat Improvement Center - CIMMYT

Lisboa 27, Colonia Juárez, Apdo. Postal 6-641, 06600, México, D.F., México.

The CIMMYT wheat program in 1998.

Jesse Dubin.

Staff status. Drs. Ravi Singh and Guillermo Ortiz were promoted to principal scientists. Drs. Monique Henry and Mohammad Mergoum were promoted to scientist, and Drs. Jannie van Beem and Belgin Cukadar, wheat breeding postdoctoral fellows, were promoted to associate scientists. Dr. Arne Hede, wheat predoctoral fellow, finished his Ph.D. and was hired as an associate scientist, triticale. CIMMYT's new office in Almaty, Kazakstan, is headed by Dr. Muratbek Karabayev. Dr. Julie Nicol, postdoctoral fellow, arrived in 1998 to work on soilborne diseases of wheat.

Happenings. Dr. Rajaram, director of the Wheat Program, was awarded the prestigious Rank Prize together with Dr. G. Khush, IRRI, for their contributions to increasing food production in the developing world. Dr. Rajaram also was given the Friendship Award by the Chinese government for his contributions to China's agricultural development. The Friendship Award is the highest honor that China can bestow on foreigners.

In March, the wheat program hosted participants from the Australian Cooperative Research Centre for Molecular Plant Breeding. The CIMMYT biotechnology group and wheat program are members of the CRC. An international review also was held of the Genetic Resources Information Package II during March. In May, a crop modeling workshop was held for wheat and maize, and in December there was a workshop for Australian and CIMMYT scientists on understanding 'G x E' to help improve breeding efficiency and germplasm transfer.

A report on the 1998 CIMMYT wheat improvement training course.

R.L. Villareal and O. Bañuelos.

The CIMMYT wheat improvement training course is intended to build skills for planning, conducting, and leading practical and comprehensive breeding programs at the national level. The basic course focuses on the identification of farmer and market needs in relation to plant and grain type and biotic and abiotic constraints that limit production in various geographic areas. Participants learn to identify germ plasm sources and the most efficient breeding technologies to be used in a breeding program. They learn how to characterize varieties and lines, maintain improved germ plasm, and produce basic seed and commercial germ plasm. The course emphasizes research on germ plasm improvement and crop management, but other important topics in agriculture are included.

The 1998 wheat improvement course started on 23 February, 1998, at Ciudad Obregon, Sonora, and ended on 27 August at CIMMYT's main headquarters in El Batan, Texcoco, near Mexico City. Fourteen wheat scientists from 10 countries participated in the course. The group included of four participants from Asia (China, Pakistan, and Thailand), four from Africa (Ethiopia and Sudan); and six from the Middle East and Europe (Egypt, Iran, Tunisia, Turkey, and Yugoslavia). A participant from Yugoslavia was enrolled for the first time. All participants are employed in wheat improvement and production research and averaged 5.3 years experience with their national programs. All were assured of occupying the same job position after CIMMYT training with 80 to 100 % of their time expected to be spent on wheat. Others will have additional responsibilities on other crops, i.e., corn, teff, or rice. This year's distinguished course lecturers included Dr. Rollin Sears from Kansas State University on plant breeding and Dr. Robert McIntosh from the University of Sydney on wheat rust pathology. All trainees assessed their training in positive terms and considered it to be very successful. Participants were coöperative and highly motivated throughout the course. A new group of trainees arrived in Mexico during the last week of February 1999 for 6 months of training.

Salt tolerance screening of durum-based synthetic hexaploids.

Diaz de Leon, A. Mujeeb-Kazi, and R.L. Villareal.

Our salt tolerance-screening priority at CIMMYT has been with Th. bessarabicum, Ps. juncea, Th. elongatum, Th. disticha, L. racemosus, and recently on Ae. tauschii through screening of synthetic hexaploids. The hydroculture screening of advanced derivatives for salinity levels between 0 and 250 mol/m3 maintained by NaCl together with growth-related parameters and Na and K estimations for establishing K/Na discrimination values were the protocols used. These are identical to those adopted in the laboratory in Bangor, Wales (Gorham 1990, Gorham et al. 1987).

From the wide array of synthetic hexaploids (T. turgidum / Ae. tauschii) produced in CIMMYT and after an initial field screen in Baja California (sea water dilution from 8 to 24 d), we selected a few promising salt-tolerant types from the synthetic germ plasms that were subsequently evaluated in hydroculture (Table 1). The expected differences in Na and K concentrations in the leaf sap are caused by the presence of the enhanced K/Na discrimination character in the hexaploids but not in the tetraploids. The dry weights and satisfactory K/Na discrimination values of the synthetic hexaploids indicate that the Ae. tauschii D genome is the carrier for this trait. Maximum Ka:Na differentiation is obtained at 50 mM, but higher levels of NaCl can be utilized. We have focused on capturing the expression of the stress trait in a workable background (synthetic hexaploid) for bread wheat improvement and not screening Ae. tauschii accessions per se.

References.

Gorham J. 1990. Salt tolerance in the Triticeae: K/Na discrimination in Aegilops species. J Exp Bot 41:615-621.

Gorham J, Hardy C, Jones RGW, Joppa LR, and Law CN. 1987. Chromosomal location of a K/Na discrimination character in the D genome of wheat. Theor Appl Genet 74:584-588.

Waterlogging tolerance of synthetic bread wheats under field conditions.

R.L. Villareal, O. Bañuelos, K.O. Sayre, M. Van Ginkel, and A. Mujeeb-Kazi.

Typical responses in wheat to waterlogging are early senescence, slower root growth, cessation of seminal root growth, and decreased nutrient accumulation. The effect of flooding on wheat is serious at crown root initiation, flowering, and grainfilling. The main objective of the study was to evaluate the waterlogging tolerance of 95 elite synthetic hexaploid wheats derived from 'T. turgidum / Ae. tauschii' crosses developed by CIMMYT's Wheat Wide Crosses Program under field conditions in northwest Mexico. The study was conducted at the Mexican National Institute of Forestry, Agriculture and Livestock, CAEVY research center near Ciudad Obregon, Sonora, Mexico, during the 1996-97 and 1997-98 crop seasons. The trials were arranged in an alpha-lattice design with two replications. An experimental unit consisted of 3-row plots, 20 cm apart and 2 m long. Seeding was by machine in dry soil at the rate of 100 kg/ha followed by a light, uniform irrigation. Waterlogged conditions were established using flooded basins measuring 12 m wide x 11 m long. Test materials were subjected to waterlogging treatment for 7 weeks, beginning 15 days after emergence, to allow uniform crop emergence until about boot stage. For the entire waterlogging treatment, continuous standing water was maintained within a range of approximately 3-8 cm. The basins then were dried, and two additional short-term irrigations were given at 2-week intervals to allow nonstress maturing.

Results of the waterlogging screening tests involving 95 synthetic hexaploids and three bread wheat check cultivars are summarized in Table 2. The degree of leaf chlorosis on a plot basis was used as the principal criterion for waterlogging tolerance. Evaluation scores were made a day after the 7-week water stress treatment to avoid interaction due to recovery of the genotypes to water stress. Mean percent chlorosis over 2 years ranged from 7 % (Dverd 2 / Ae. tauschii 221) to 75 % (Altar 84 / Ae. tauschii 188) with an overall mean of 43 %. Five synthetic entries had leaf chlorosis scores less than 10 % as compared to 14 %, 17 %, and 75 % leaf chlorosis scores of the bread wheat checks Ducula, Pato Blanco, and Seri M82, respectively.

The mean grain yield/spike of the synthetics was 1.37 g. The synthetic 'D67.2 / P66.270 // Ae. tauschii (221)' had the highest yield/spike (2.19 g), whereas 'Botno / Ae. tauschii (625)' had the lowest (0.62 g). Seventy-six percent of the test entries had flowering dates later than the checks. The mean number of days to flowering for all synthetics was 109. Forty entries were taller than the checks, measuring more than 88 cm. The tallest was 'Lck59.61 / Ae. tauschii (324)' at 99 cm, and the shortest were 'Falcin / Ae. tauschii (312)' and 'CROC1 / Ae. tauschii (517)' at 67 cm. The average height of all the entries was 81 cm. For 1,000-kernel weight, 75 % of the test materials had heavier grains (40.8­53.3 g) than the check cultivars. The mean 1,000-kernel weight was 44.8 g for all the synthetics. The heaviest grains (53.3g) were produced by the '68.111 / RGB-U // WARD /3/ Ae. tauschii (511)' synthetic.

Screening of synthetic hexaploids to aluminum toxicity tolerance under laboratory conditions.

J. Lopez-Cesati, R.L. Villareal, and A. Mujeeb-Kazi.

Aluminum toxicity generally is associated with low soil pH (below 5.5) and increases severely when the pH falls below 5.0. Such low pH values increase considerably the aluminum solubility in the soil, where more than half of the cationic exchange sites can be taken up by aluminum. Aluminum also can interfere with phosphorus metabolism by causing an accumulation of high quantities of inorganic phosphates within the roots, thereby reducing their ability to absorb and transport this important element. Management alternatives can correct acid soil problems. However, different cereal species and varieties within the same species also vary widely in their tolerance to high aluminum levels in acid soils that could be exploited through breeding.

An elite set of 95 elite synthetic hexaploids from CIMMYT and their durum wheat female parents were tested for Al+3 tolerance. The screening methodology used was described earlier by López-Cesati et al. (1986). The method is based on the fact that Al+3 tolerance in wheat is largely a function of Al+3 exclusion from the roots. The scoring (1­3) scale relates well with Al+3 tolerance of the annual/perennial Triticeae germ plasm. This scale corresponds to root tip growth after immersion of the roots in a nutrient solution containing 46 ppm of aluminum, subsequent staining of the roots with an aqueous solution of 0.2 % hematoxylin, and observation for any continued root growth. Scoring categories were tolerant, medium tolerant, and susceptible. Ten seedlings were tested for each entry. The tolerant and susceptible bread wheat check cultivars, CNT-1 and Glennson 81, respectively, also were included.

Interspecific hybrids between T. turgidum and Ae. tauschii have led to production of several synthetic hexaploids, with which screening may enable identification of the D-genome Al+3 tolerance and provide another diversity resource for wheat improvement. However, in the 95 synthetic wheats screened, no tolerance was observed. All synthetic entries were just as susceptible as their durum parents and the susceptible Glennson 81 bread wheat check. Although we did not screen the Ae. tauschii accessions, this aspect could be studied further. We can safely conclude that genetic expressivity of the trait in synthetics screened was nonexistent or not expressed. Ae. tauschii germ plasm, especially those accessions collected from environments with acid soil, are solicited from coöperators for production of new synthetics at CIMMYT.

Reference.

Lopez-Cesati, J, Villegas E, and Rajaram S. 1986. CIMMYT's laboratory method for screening wheat seedling tolerance to aluminum. In: Wheat Breeding for Acid Soils, Review of Brazilian/CIMMYT Collaboration, 1974 1986 (Kohli MM and Rajaram S eds). CIMMYT, Mexico. pp. 59-65.

Relationship between grain yield of F5 individual F2 plant-derived bulk-selected families of spring bread wheat and the canopy temperature depressions measured in F3, F5, and F6 generations.

K.D. Sayre and J. Cruz Miranda.

In 1992, a cross was made between the spring bread cultivars Pitic 66 and Super Kauz. Pitic 62 had been identified in yield-potential trials of agronomic bread wheat as low yielding and characterized by a small canopy temperature depression, whereas Super Kauz was high yielding with a large canopy temperature depression.

Approximately 200 F3 individual F2 plant-derived families from the cross were grown in the 1994-95 cycle at the CIANO Experiment Station near Ciudad Obregon, Sonora, Mexico. The plots were small, 90-cm beds, 1-m long with three rows per bed. A series of canopy temperature measurements was made during the cycle, and the average of these measurements were used to identify 10 F3 families with the smallest canopy temperature depression from ambient air temperature(those with the hottest canopies) and 11 families with the largest depressions (those with the coolest canopies). In addition, 17 families were chosen at random from the 200 F3 families and 10 families that were selected by a breeder based on visual observation. There were only two cases where families were included in more than one of the above categories. One family ended up as one of the 'hot' families and one of the 'random' families. Another family ended up as one of the 'cool' families and was one of the families visually selected by the breeder. F4 seed was bulk-harvested from the F3 families without selection, and the F4 generation was grown in the 1995 summer cycle at El Batan. F5 seed was harvested, again as bulks, without any selection from the individual F4 families.

The F5 families were planted in 80-cm beds with three rows per bed, two beds per plot, 5 m long, and with three replications in a randomized complete block design at CIANO during the 1995-96 cycle. A series of canopy temperatures was taken during the cycle, and yield and other yield-related components were also measured.

In the 1996-97 cycle, the F6 bulk-selected families were planted at CIANO in two replications on 80-cm beds, one bed/plot, 2 m long, and with three rows/bed. Two canopy temperature measurements were made during the cycle, but yield was not determined.

Table 3 presents the F5 yield information and the average canopy temperature depressions for the four categories identified among the F3 families. The average F5 family yield for the hot-canopy category was lowest followed by the randomly chosen group. The average yields for the cool-canopy families and those selected visually by the breeder were similar, but there was only one family in common. The breeder and the IR gun appear to identify different high-yield potential groups of F3 families. The two selection criteria used (breeder and large canopy temperature depression) in the F3 generation arrived at similar yields but very different (except for one family in common) F5 families.

Table 3 also presents the average canopy temperature depressions for each category taken during the various segregating generations. For the most part, the hot-canopy category had the smallest canopy temperature depressions, followed by the randomly chosen category. The cool-canopy category tended to have either a slightly larger or similar canopy temperature depression when compared to the breeder-selected category.

Table 4 indicates the phenotypic correlations between the various parameters for the 46 included families. The correlations between the F5 yields and the canopy temperature depressions taken at the F3, F5, or F6 are remarkably large, especially because these represent completely unselected, F2, single plant-derived, bulked families. All correlations are highly significant.

Table 4. Correlations between grain yield in the F5 generation and F3, F5, and F6 canopy temperature
depressions (n = 46).

Factor	F5 yield	F3 canopy temperature depression	F5 canopy temperature depression	F6 canopy temperature depression
F3 canopy temperature depression	0.592	---
F5 canopy temperature depression	0.670	0.569	---
F6 canopy temperature depression	0.659	0.487	0.638	---
Correlation significance at 0.05 = 0.290 and at 0.01 = 0.377.

This rather modest experiment provides some of the first clear evidence indicating the potential utility of canopy temperature depression as an aid in early-generation selection for yield potential of spring bread wheats under irrigated, high-yield potential conditions. The research supports that of Dr. Pat Wall at CIMMYT in the late 1980s, who identified good correlation between F2 leaf stomatal conductivity characteristics and subsequent yield performance at later generations. The fact that the high-yielding group of F3 families that was identified by the IR gun was largely distinct from the population of families visually selected by a breeder suggests how effectively the breeders' eye might work in tandem with the IR gun for early generation selection. Obviously, more work is needed to develop a final, efficient selection protocol but the research reported here clearly points in that direction.

D-genome based synthetic hexaploids with multiple biotic stress resistances.

A. Mujeeb-Kazi, G. Fuentes-Davila, L.I. Gilchrist, C. Velazquez, and R. Delgado.

The primary gene pool species include the hexaploid land races, cultivated tetraploids, wild T. turgidum ssp. dicoccoides, and diploid donors of the A and D genomes to durum/bread wheats. Genetic transfers from these two genomes occur as a consequence of direct hybridization and homologous recombination with breeding protocols contribute different backcrossing and selection strategies. One avenue for using the D-genome diversity is via bridge crossing of amphiploids that are produced by hybridizing 'T. turgidum/Ae. tauschii' accessions. These synthetic hexaploids are genomically AABBDD with 2n = 6x = 42 chromosomes. We have produced 730 such synthetics so far, and biotic stress screening of several of these conducted in various Mexico locations has identified diversity for resistance to four stresses (S. tritici, H. sativum, N. indica, and F. graminearum). In general, several synthetics combine resistances for at least two or three of the above four biotic stresses (Table 5). Only one synthetic; 'Doy1/Ae. tauschii (458)', combined all four biotic resistances tested. The synthetics are being further evaluated for several other biotic/abiotic stresses. A high probability exists of identifying synthetics that may combine many more of these attributes in a single genetic stock, which then will be a definite asset in their utilization for breeding and molecular studies.

Table 5. Mean scores of some Triticum turgidum/Aegilops tauschii synthetic hexaploids (2n = 6x = 42, AABBDD) with multiple biotic stress resistances.

Pedigree **	Biotic Stress *
	Fusarium tritici	Septoria sativum	Helminthosporium indica	Neovossia graminearum
Altar 84/Ae. tauschii (188) [CIGM87.2765]	S	S	0	16.9
Altar 84/Ae. tauschii (192) [CIGM87.2767]	2-1	S	0	S
Altar 84/Ae. tauschii (198) [CIGM87.2768]	2-1	S	0.5	13.0
Cpi/Gediz/3/Goo//Jo69/Cra/4/Ae. tauschii (208) [CIGM88.1194]	S	S	0	11.1
Yuk/Ae. tauschii (217) [CIGM90.561]	2-1	S	0	15.4
68112/Ward//Ae. tauschii (369) [CIGM88.1313]	S	S	0	7.8
Doy 1/Ae. tauschii (447) [CIGM88.1344]	1-1	S	0	15.7
68.111/Rgb-u//Ward/3/Fgo/4/Rabi/5/Ae. tauschii (629) [CIGM90.590]	3-2	3-2	0	S
Fgo/Usa2111//Ae. tauschii (658) [CIGM89.506]	2-1	2-2	1.8	S
68.111/Rgb-u//Ward/3/Fgo/4/Rabi/5/Ae. tauschii (878) [CIGM89.559]	2-1	2-2	2	S
Yav 2/Tez//Ae. tauschii (249) [CIGM88.1239]	S	S	0	14.5
Gan/Ae. tauschii (180) [CIGM90.799]	1-1	S	0.8	11.3
Lck59.61/Ae. tauschii (313) [CIGM90.812]	3-2	S	0	10.6
Sca/Ae. tauschii (518) [CIGM90.845]	3-2	3-2	0	S
Yar/Ae. tauschii (518) [CIGM90.846]	3-2	3-2	0	S
Snipe/Yav79//Dack/Teal/3/Ae. tauschii (700) [CIGM90.897]	3-2	4-3	0	S
Gan/Ae. tauschii (897) [CIGM90.911]	3-2	2-2	0	S
Yav 2/Tez//Ae. tauschii (895) [CIGM90.910]	3-2	3-3	0	S
Doy 1/Ae. tauschii (458) [CIGM92.1727]	3-2	4-3	0	15.1
Green/Ae. tauschii (458) [CIGM92.1871]	S	3-2	0	S
Ceta/Ae. tauschii (174) [CIGM93.183]	S	S	0	13.9
Sty-us/Celta//Pals/3/Srn 5/4/Ae. tauschii (502) [CIGM93.261]	1-1	3-3	0.4	S
Ceta/Ae. tauschii (1024) [CIGM93.297]	S	S	0	13.0
Dverd 2/Ae. tauschii (1027) [CIGM93.300]	2-1	2-1	0.7	S
Ceta/Ae. tauschii (1027) [CIGM93.406]	3-2	S	0	11.8
* Septoria tritici and Helminthosporium sativum rated on a double-digit modified scale: the first digit indicates the height of infection, where 1 = lowest leaf; 5 = up to mid-plant; and 9 = up to flag leaf; the second digit indicates disease severity on infected leaves, where 1 = 10 % coverage; 5 = 50 % coverage; and 9 = 90 % coverage. Values for Neovossia indica and Fusarium graminearum are in percentages. S = Susceptible with scores over 3-2 for Septoria, 4-3 for H. sativum, 1.8 % for Karnal bunt, and 15.7 % for scab. ** Synthetic hexaploid with the Ae. tauschii CIMMYT accession number in parentheses, and the CIMMYT cross number in brackets.

Fusarium graminearum resistance in alien germ plasm and in a bread wheat/alien species derivative with multiple biotic stress resistances.

A. Mujeeb-Kazi, L.I. Gilchrist, G. Fuentes-Davila, C. Velazquez, and R. Delgado.

Of the primary gene pool Triticeae species, we have given priority to Ae. tauschii for wheat improvement. Bridge crosses utilizing the D genome via synthetic hexaploids provide a potent means of improving bread wheats. Screening the synthetic hexaploid (SH) wheats has identified resistance diversity for F. graminearum. Some resistant SH wheats also have been utilized for bread wheat (BW) improvement, and the resulting BW/SH advanced derivatives further express the parental SH resistance diversity.

Some of the SH wheats most resistant to F. graminearum during 3 years of field screening at Toluca, Mexico, are presented in Table 6. SH wheats have less than 15 % infection, similar to the resistant BW checks Sumai and Frontana. The susceptible check cultivar Flycatcher ranged between 24.6 and 45.5 %. The susceptible durum wheat Altar 84 scored 48.3 to 53.5 %. A high degree of resistance has further been identified in 'BW/SH' advanced derivatives. These germ plasms have Type II (spread) resistance. The advanced derivatives also possess Type I (penetration) and III (toxin level) resistances. One of the most promising combinations is 'Mayoor//TKSN1081/Ae.tauschii'. Apart from its high level of scab resistance (Table 6), this advanced line has multiple resistances to S. tritici, N. indica, and H. sativum (Table 7). This line is currently being used to develop an F1-based DH mapping population of 500 DH's. The BW cultivar used in this population is susceptible to all four of these stresses.

Advanced derivatives from bread wheat/D-genome synthetic hexaploid combinations resistant to Helminthosporium sativum.

A. Mujeeb-Kazi and R. Delgado.

Ten lines with resistance to H. sativum were reported in Volume 44, Annual Wheat Newsletter 1998. To this set, we added another 13 lines to make the entry total 23, apart from the susceptible check cultivar Ciano 79. One of the entries included was derived from Ae. searsii and was the earliest to flower and had a high level of resistance. Three entries were derived from resistant/resistant advanced 'BW/SH' lines with different Ae. tauschii accessions in their pedigrees.

This study had greater stringency, in that observations were recorded for days to flowering, days to physiological maturity, and plant height. Progressive infection scores also were recorded at 58, 65, 72, 79, 89, and 96 days after planting. Additionally, we recorded grain finish and yield data. All the above observations were combined in a replicated study on fungicidal treatment or no fungicidal treatment of the plots. Yield and fungicide treatment results are not reported here.

Helminthosporium sativum-resistant double haploid lines derived from bread wheat/D-genome synthetic hexaploids.

A. Mujeeb-Kazi, S. Cano, V. Rosas, and R. Delgado.

We are distributing H. sativum-resistant germ plasm globally based upon the resistance observed under Mexican conditions in Poza Rica, Mexico. Several countries are recipients of the germ plasm. In order to provide stable genetic material to our collaborators, we decided to develop double haploids, retest their performance, increase seed, and then distribute them. Such germ plasms will be homozygous and facilitate disease screening across many locations.

Ten of these double haploid germ plasms, derived from 'bread wheat/D genome synthetic hexaploids' or 'bread wheat/perennial Triticeae//maize' combinations, were produced and evaluated for days to flowering, days to physiological maturity, plant height, progressive disease infection score, and grain finish. Susceptible bread wheats were Ciano, Bacanora, Opata, and Yaco. The results are presented in Table 9. Disease progress and final score (2-2 to 3-3) from 65 days to 96 days are indicative of the superiority of the resistant DH lines over the bread wheat susceptible checks (7-7 to 9-9; see Table 9). The resistant lines had well-filled grain versus blemished or shrivelled grain for the susceptible wheats (1 or 2 versus a score of 3-4).

Doubled haploid-mediated gene pyramiding among some D-genome synthetic hexaploids for Helminthosporium sativum resistance.

A. Mujeeb-Kazi, S. Cano, V. Rosas, and R. Delgado.

Biotic stress like H. sativum in bread wheat has been until recently one of the main constraints that required improvement. Resistance incorporation at the level of synthetic hexaploids has been satisfactorily accomplished and involves several Ae tauschii accessions.

Because the utilization of these synthetics is for bread wheat improvement, we report here the development of novel synthetic stocks that attempt to pyramid the contribution of various Ae. tauschii accessions. Such stocks allow access for simultaneous multigene introgressions when they are crossed onto bread wheat cultivars.
The disease progressed slowly in most of the test derivatives of the advanced 'BS/SH' lines. These lines maintained a very high level of resistance up to 96 days when the crop was near maturity. The grain finish ranged between 1 to 3. The susceptible BW cultivar Ciano had poor grain finish and a highly susceptible disease score of 9 9 (Table 8). Observations for days to flowering, maturity, and plant height are all assets for multilocational global testing of these germ plasms, although lateness and taller plants are impediments in their breeding utilization.

The protocol involved crossing together two H. sativum-resistant synthetic hexaploids. Individual selections were made from the segregating F2 populations of each combination, and DHs were produced on these selections. The detached spike procedure for haploid production was employed with maize as the pollen source for inducing haploidy. The doubled haploids were tested in Poza Rica, Mexico, and observed for days to flowering, days to physiological maturity, plant height, progressive infection score, and grain finish. The DH's have combined accessions 236/447, 236/895, 434/895, 447/895, and 629/895 and show extremely high levels of resistance, as evident from disease scores ranging from 2-2 to 3-3 over the crop cycle (Table 10). The disease progress in these lines was slow compared to the susceptible bread wheats, and grain finish ranged between 1 and 2.

This germ plasm is now being incorporated in our prebreeding program. The pyramiding approach will add greater emphasis for this and other stresses when our molecular group elucidates the uniqueness of each accession prior to our putting other SH combinations together.

Elite 'bread wheat / D genome synthetic hexaploid' germ plasm resistant to Karnal bunt.

A. Mujeeb Kazi and G. Fuentes-Davila.

Eleven spring wheat germ plasm lines (CIGM90.257-1, CIGM90.257-2, CIGM91.61-1, CIGM91.61-2, CIGM90.462, CIGM90.248-1, CIGM90.248-2, CIGM90.261, CIGM90.250-1, CIGM90.250-2, and CIGM90.412) were developed for improved resistance to Karnal bunt. The lines were derived from resistant SHs crossed with the Karnal bunt-susceptible bread wheat cultivars Flycatcher, Kauz, Yaco, Borlaug, and Papago M86. Segregating generations of the crosses were advanced by pedigree breeding. The mean agronomic performance and disease scoring data of 11 germ plasm lines resistant to Karnal bunt over 6 years of field tests are presented in Table 11.

The boot inoculation test for evaluation of resistance to Karnal bunt was conducted at the Mexican Institute of Forestry, Agriculture, and Livestock (INIFAP), Campo Agrícola Experimental Valle del Yaqui (CAEVY) Research Station, Sonora, Mexico, over 6 years ending in the 1997-98 crop cycle. Disease score was based on the number of infected and healthy kernels in a plot. The 'SH/BW' lines gave less than 2.5 % infection to Karnal bunt in all tests, compared with a 30 % mean infection of WL711. Other susceptible bread wheat check cultivars Kauz, Seri, and Flycatcher had infections of 33.8, 13.5, and 41.3, respectively (Table 11). All lines had good agronomic plant type and were high yielding under optimum disease free environments.

Table 11. Pedigree, days to anthesis and physiological maturity, plant height, 1,000-kernel weight, and Karnal bunt (Neovossia indica, KB) ratings of 11 susceptible bread wheat/resistant synthetic hexaploid advanced resistant lines.

Identification	Pedigree *	Anthesis	Days to physiological maturity	Plant height (cm)	1,000-kernel weight (g)	KB score mean over 6 years
CIGM90.257-1	Croc 1/Ae. tauschii (205)//FCT	88	126	75	38.8	1.59
CIGM90.257-2	Croc 1/Ae. tauschii (205)//FCT	92	126	85	37.5	1.81
CIGM91.61-1	Croc 1/Ae. tauschii (224)//Kauz	79	123	95	46.8	0.69
CIGM91.61-2	Croc 1/Ae. tauschii (224)//Kauz	88	126	90	41.0	2.42
CIGM90-462	Altar 84/Ae. tauschii (221)//Yaco	88	126	90	53.8	0.95
CIGM90.248-1	Croc 1/Ae. tauschii (205)//Kauz	92	126	80	42.0	0.77
CIGM90.248-2	Croc 1/Ae. tauschii (205)//Kauz	92	126	85	41.8	2.09
CIGM90.261	Croc 1/Ae. tauschii (205)//Kauz	92	126	100	46.0	1.19
CIGM90.250-1	Croc 1/Ae. tauschii (205)//Borl 95	79	126	90	51.1	1.57
CIGM90.250-2	Croc 1/Ae. tauschii (205)//Borl 95	79	126	85	51.8	0.86
CIGM90.412	Croc 1/Ae. tauschii (213)//Pgo	79	123	100	50.0	1.97
	Kauz (susceptible bread wheat)	83	135	85	33.8	9.92
	Seri (susceptible bread wheat)	83	140	80	30.5	28.36
	Flycatcher (susceptible bread wheat)	79	135	70	41.3	29.0
	WL-711 (susceptible bread wheat)	82	131	70	35.8	30.0
* Synthetic hexaploid with the Ae. tauschii CIMMYT accession number in parentheses.

Reference.

Warham EJ. 1984. A comparison of inoculation methods for Karnal bunt (Neovossia indica). Phytopathology 74:856-857.

Publications.

Inagaki MN and Mujeeb-Kazi A. 1998. Production of polyhaploids of hexaploid wheat using stored pearl millet pollen. Euphytica 100:253-259.

Inagaki M and Mujeeb-Kazi A. 1998. Efficient techniques for polyhaploid production in hexaploid wheat using pearl millet crosses. In: Triticeae III (Jaradat AA ed). Science Publishers Inc, Enfield, NH. pp. 97-102.

Inagaki MN, Pfeiffer W, Mergoum M, and Mujeeb-Kazi A. 1998. Variation of the crossability of durum wheat with maize. Euphytica 104:17-23.

Inagaki MN, Varughese G, Rajaram S, Van-Ginkel M, and Mujeeb-Kazi A. 1998. Comparison of bread wheat lines selected by doubled haploids, single-seed descent and pedigree selection methods. Theor Appl Genet 97:550 556.

Mujeeb-Kazi A. 1998. Analysis of the use of haploidy in wheat improvement. In: Biotechnology Symposium, Uruguay (Kohli M ed). 19­21 Nov, 1998.

Mujeeb-Kazi A. 1998. Evolutionary relationships and gene transfer in the Triticeae. In: Triticeae III (Jaradat AA ed). Science Publishers Inc, Enfield, NH. pp. 59-65.

Mujeeb-Kazi A and Delgado R. 1998. Bread wheat/D genome synthetic hexaploid derivatives resistant to Helminthosporium sativum spot blotch. In: Proc 9th. Inter Wheat Genet Symp (Slinkard AE ed). University Extension Press, Saskatoon, Canada. 3:297-299.

Mujeeb-Kazi A and Rajaram S. 1999. Transferring alien genes from related species and genera. Chapter for FAO Wheat Book (in press).

Mujeeb-Kazi A, Gilchrist LI, Fuentes-Davila G, and Delgado R. 1998. D genome synthetic hexaploids: production, and utilization in wheat improvement. In: Triticeae III (Jaradat AA ed). Science Publishers Inc, Enfield, NH. pp. 369-374.

Mujeeb-Kazi A, Gilchrist LI, Villareal RL, and Delgado R. 1998. Registration of ten wheat germplasm lines derived from Triticum aestivum//T. turgidum/Aegilops tauschii crosses resistant to Septoria tritici leaf blotch. Crop Sci (in press).

Mujeeb-Kazi A, Rosas V, Cortes A, William MDHM, Villareal RL, and Delgado R. 1999. Registration of homozygous T1BL·1RS chromosome substitution line germplasms of Triticum turgidum L. cv. Altar 84. Crop Sci (in press).

Singh RP, Mujeeb-Kazi A, and Huerta-Espino J. 1998. Lr46: A gene conferring slow rusting resistance to leaf rust in wheat. Phytopathology 88:890-894.

Trethowan R, Villareal RL, and Mujeeb-Kazi A. 1998. Pre-harvest sprouting tolerance among synthetic hexaploid wheats. In: Proc 8th Inter Symp Pre-harvest Sprouting in Cereals, Detmold, Germany.

Villareal RL and Mujeeb-Kazi A. 1998. Exploiting synthetic hexaploids for abiotic stress tolerance in wheat. In: Proc Wheat Workshop, South Africa.

Villareal RL, Bañuelos O, Mujeeb-Kazi A, and Rajaram S. 1998. Agronomic performance of chromosome 1B and T1BL·1RS genetic stocks in spring bread wheat (Triticum aestivum L.) cultivar Seri M82. Euphytica 103:195 202.