ITEMS FROM MEXICO

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 1997.

Jesse Dubin.

Staff status. Gene Saari, regional pathologist in south Asia, retired after 28 years at CIMMYT and the Ford Foundation. Several staff were transferred. Etienne Duveiller, pathologist in Mexico, was moved to south Asia with his base in Nepal. Guillermo Ortiz, wheat breeder, was moved from the CIMMYT Program based at ICARDA and also was relocated to Nepal. Osman Abdalla, breeder, replaced Guillermo at Aleppo, and Tom Payne, breeder, replaced Osman in Ethiopia.

Happenings. CIMMYT/BADC/Catholic University, Louvain, sponsored a symposium on Helminthosporium leaf blights in February. Over 70 scientists participated and presented papers. The proceedings are scheduled for publication in early 1998. The North American Cereal Rust Workers met at CIMMYT in August and about 30 scientists attended.

Program status. As noted in Vol 43 of the AWN, we are evolving toward project-based research focused on outputs for our clients. In late 1997, we moved towards this goal and are continuing the process into 1998.

CIMMYT was reviewed extensively by an external panel of eminent wheat scientists in 1997. The Wheat Program was given high marks and congratulated for the quality of its research, germplasm outputs, and impact in developing and developed countries.

CIMMYT wheat improvement training - an update.

R.L. Villareal and O. Bañuelos.

CIMMYT believes that well trained scientists are the keys to the future of the national research programs. More than 600 wheat improvement in-service trainees from more than 80 developing countries worldwide have completed this course since the establishment of CIMMYT in 1966. Regional distribution of participants during the past 30 years is shown in Table 1.

The impact of the CIMMYT wheat improvement training program on the human resource capacities in the developing world has been substantial. Reports have indicated that scientists trained by CIMMYT are active in over 100 national programs, indicating the importance of a wheat improvement training course for increasing the research capacity of personnel for crop institutions throughout the world. Independent surveys of those individuals have shown that many consider their training at CIMMYT to be among the most significant professional development phases in their careers. High among the salient aspects identified by former trainees are the practical skills and confidence they acquire in how to design and execute a field research program. CIMMYT trainees invariably have a high reputation within their national programs for high motivation and the capacity to achieve research and production results.

CIMMYT's wheat improvement training program is a practical, field-oriented course in many aspects of wheat breeding, pathology, and production. The program is flexible and highlights the need for international coöperation in nursery evaluation and germplasm development. The ultimate result of this approach to training is the creation of an international network of scientists involved in the development and release of widely adapted, high yielding, and disease-resistant varieties. These are essential components to further the production of wheat in the developing world. Many alumni of the CIMMYT training programs have moved into administrative positions within their own national programs. Thus, there are continuing needs to train young promising researchers to replace them, and to maintain a critical mass of knowledgeable and field-oriented wheat scientists. Wheat improvement training at CIMMYT is projected to continue at the present level for the time being but will increase when possible. Serious consideration is being given to developing an advanced wheat improvement course for senior-level national-program staff. A new group of trainees will arrive in Mexico during the last week of February, 1998, for 6 months of training.

Performance of a homozygous 1B substitution versus the Seri 82 T1BL·1RS genetic stocks under drought stress conditions.

R. L. Villareal, O. Bañuelos, A. Miranda, A. Mujeeb-Kazi, and S. Rajaram.

Wheat varietal releases possessing the T1BL·1RS translocation currently occupy over 5 million hectares of cultivated area worldwide. Fifty percent of CIMMYT's current high-yielding bread wheat advanced lines possess the T1BL·1RS translocation derived from winter wheat cultivars Kavkaz, Aurora, and Weique Redmace. Thus, an experiment to truly demonstrate the impact of the T1BL·1RS wheat cultivars was necessary. To study the effect of T1BL·1RS on agronomic performance of wheat, 20 related spring bread wheat genetic stocks from cultivar Seri 82 (10 homozygous for a 1B substitution and 10 homozygous for T1BL·1RS) were seeded in a randomized complete block design under reduced (one irrigation) moisture conditions in northwest Mexico. Data were obtained on grain yield, yield components, and other agronomic characteristics for two consecutive production cycles.

A positive effect of the T1BL·1RS on agronomic traits was detected under reduced irrigation conditions (Table 2). Based on the means across the test genotypes, increases were observed in the T1BL·1RS lines for grain yield (11.3 %), aboveground biomass at maturity (6.3%), harvest index (4.1 %), spikes/m2 (6.2 %), grains/m2 (7.2 %), 1,000-kernel weight (3.3 %), and test weight (3.5 %) as compared to the 1B genotypes. Moreover, anthesis and physiological maturity of the T1BL·1RS genotypes were delayed by 2 and 2.2 days, respectively. Differences between the chromosome translocation groups for grains/spike, plant height, spike length, and grain-filling period were nonsignificant. The superior performance of the translocation lines in this study suggests that the 1BL chromosome arm possesses genes that interact favorably with the 1RS rye chromosome arm.

Drought tolerance of synthetic bread wheats (Triticum turgidum x Aegilops tauschii).

R. L. Villareal, O. Bañuelos, J. Borja, and A. Mujeeb-Kazi.

Aegilops tauschii is a rich source of variation for many agronomically important traits and could be tapped as a possible source of germplasm for enhancing drought tolerance in bread wheat. Two trials were conducted at the Mexican National Institute of Agriculture, Livestock and Forestry Research Center at Sonora, Mexico, to evaluate the drought tolerance of 61 elite synthetic hexaploids (T. turgidum / T. tauschii) produced by our Wide Crosses Program under reduced (one irrigation) moisture conditions. Outstanding synthetic hexaploid genotypes possibly could be identified for utilization in the improvement of T. aestivum. Grain yield, yield components, and other agronomic traits were determined. Three drought-tolerant bread wheat cultivars (Nesser, Dharwar Dry, and Sitta) were used as checks.

Table 3 presents the 12 best yielders among the 61 synthetic hexaploid lines tested during the 2 years of replicated yield trials. Yields of the synthetics ranged from 638 kg/ha (D67.2/P66.270//Ae. tauschii 218) to 4,037 kg/ha (Gan/Ae. tauschii 897), with an overall mean yield of 2,098 kg/ha. The highest yielding synthetic was comparable to the highest yielding check cultivar, Nesser (4,065 kg/ha). The yields of the other bread wheat checks were 3,276 kg/ha for Dharwar Dry and 3,166 kg/ha for Sitta. Mean biomass yield ranged from 5.53 T/ha (Altar 84/Ae. tauschii 219) to 13.8 T/ha (Lck59.61/Ae. tauschii 324). Eighteen synthetic lines had better biomass yield at maturity than the highest biomass yielding check, Nesser (10.8 T/ha). Thousand-kernel weight was significantly heavier for all the synthetic genotypes when compared to the check cultivars. Their mean 1,000-kernel weight ranged from 33.4 g (Botno/Ae. tauschii 625) to 51.2 g (Doy 1/Ae. tauschii 428) with an overall average of 42.2 g.

However, these observed advantages do not imply direct commercialization of the material, because other characteristics still need to be improved and stabilized through breeding (e.g., tight threshability, lodging susceptibility). Different yield responses presumably were due to gametic contribution and variability of the synthetic's progenitors.

More than 650 synthetic hexaploids have been developed by our Wide Crosses Program to date, the majority involving a unique Ae. tauschii accession. This germplasm consists of spring types that are highly crossable to advanced bread wheats, thus offering an easier route for their practical utilization and global distribution. As screening data on biotic/abiotic resistance/tolerance of synthetics become available, we anticipate that efforts to hybridize elite synthetics with our current, high-yielding, advanced lines will increase.

Triticale.

Mohamed Mergoum.

Introduction. Recent estimates indicate that more than 2.6 million ha are planted to triticale compared to 0.87 million ha in 1986. Triticale's contribution to grain production alone is more than 8 million metric tons per year. The advantage of triticale over other small grains such as wheat is its ability to grow and produce high grain and biomass yields under a wide range of soil and climatic conditions. In regions where favorable rainfall conditions prevail, foliar diseases (leaf rust, Septoria, and powdery mildew) frequently can cause epidemics on cereals. However, triticale consistently showed better resistance to these disease. Triticale also has multiple end-uses for animal and human consumption.

Triticale improvement at CIMMYT concentrates on (1) generating genetic variability within the spring, facultative, and winter triticale gene pool; (2) distributing improved triticale germplasm that is adapted to a wide range of adverse climatic and soil conditions to the National Agricultural Reseach System (NARS) in both developing and developed countries; and (3) providing alternatives for end uses.

Additional new avenues of triticale improvement will consider gene transfer, particularly genes associated with bread making, disease resistance, and the incorporation of desirable agronomic traits from bread wheat to triticale. Further activities include the exploitation of heterosis through triticale hybrid development and the investigation on mixtures to enhance its productivity.

Progress in triticale grain yield potential (M. Mergoum and W. Pfeiffer). At Obregon, Sonora, in northwest Mexico (27.5°N, 40 m asl), CIMMYT triticale breeding efforts are concentrated on raising the productivity of triticales targeted for different mega-environments (ME), particularly ME1 (irrigated) and ME4 (drought stress). Considerable progress has been made in improving grain yield of spring triticale at CIMMYT in recent years for the ME1 and ME4 environments. During the last two crop cycles at Ciudad, Obregon, 45 yield trials comprising more than 2,500 lines were conducted under both irrigated and moisture-stress conditions. In addition to 1,500 advanced lines, 400 F5 and 600 F4 derived lines were yield tested.

Frequency distributions of the lines in the yield tests, based on grain yield expressed as a percentage of Fahad-5 (check, yield 5.9 tons/ha) under irrigation, showed an increasing frequency of genotypes that equal or surpass the check yield. However, in yield trials involving F4 and F5 derived lines, only 81 ( 21 %) and 98 (16 %) lines showed the same or higher yields compared with check, respectively. In advanced yield trials, 253 F4 (45 %) and 396 F5 (42 %) lines had equal or higher yields compared with Fahad-5. This result indicates the efficiency of phenotypic and early yield testing. Absolute grain yields were relatively high and reached 7.6 T/ha. The highest yielding genotypes from advanced, F4, and F5 yield trials outperformed Fahad-5 by 132 %, 122 %, and 120 %, respectively.

Triticale mixtures: a way to improve and stabilize yield under adverse environments (M. Mergoum and W. Pfeiffer). Two mixture studies were conducted at Obregon during the 1995-96 crop cycle under both irrigation and moisture-stress conditions to evaluate population buffering effects. The first study (Mixt. 1) included eight groups of three pure-sister lines and their mixtures. In the second study (Mixt. 2), the different genotypes and their two- and three-component mixtures were evaluated for agronomic performance. Results of grain yield performance from both studies were collected.

In the Mixt. 1 study, the grain yields of the mixtures (between sister lines) showed an overall advantage of mixtures over both pure lines and the check Fahad-5 under irrigation and more a pronounced under moisture stress. Crosses where mixtures showed superior yield performances over the pure lines and the check included group 2 (Anoas 3 / Tatu 4) and group 7 (Rhino 3 / Bull 1-1) under irrigation, and group 4 (CMH77a.1024 / 2*Yogui // Lamb 4) and group 6 (Gnu / Asad // Ard /3/ Manati 1) under drought.

Similar results were obtained in the in the Mixt. 2 study. The frequency distributions of mixtures of genotypes derived from different crosses resulted in several mixtures with significantly higher yields than their components under irrigation and drought conditions. Although the best genotypes surpassed the check by 9 % (irrigated) and 12 % (drought), the highest yielding mixtures produced 12 % and 27 % higher grain yields compared with Fahad-5 under irrigation and drought conditions, respectively. Mixtures involving the cross 'Supi 3 / Hare 7265 // Yogui 1', the highest yielding triticale advanced line for the last 3 years, were consistently the top-yielding under all conditions.

Performance of triticale hybrids (W. Pfeiffer, M. Mergoum, and K Sayre). This study, conducted in Obregon, included 41 triticale hybrids produced via chemical hybridizing agents (CHA). These hybrids were evaluated for their agronomic performance and physiological traits under full irrigation at Obregon during two crop cycles. Grain yield for the 41 hybrids showed substantial heterosis, up to 27 % of high parent. Hybrids that yielded less than the low parent generally had very high biomass, but the harvest index was low because of excessive plant height and late maturity. The results suggest a high payoff using triticale hybrids in raising and stabilizing triticale's potential production.

Performance of Triticale Substituted Lines (W. Pfeiffer, M. Mergoum, J. Pena, and A. Lukazewski). International yield trials and recent variety releases suggest an adaptive advantage of complete triticales carrying the 6D(6A) substitution. Comparison of near isogenic Rhino 6D(6A) and its 6A(6A) controls indicates significant genetic gains for grain yield for Rhino carrying 6D(6A) under both irrigated and moisture stress conditions. The adaptive advantage associated with the 6D(6A) substitution suggests the exploitation of other D(A), D(B), and D(R) substitutions and/or translocations by triticale breeders to enhance triticale's agronomic performance.

Eighty-two sister lines reselected from a Rhino substitution series developed by A.J. Lukaszewski (University of California, Riverside) and their controls were planted under full and limited irrigation at Obregon and Toluca (located in the highland of central Mexico, 18°N and 2,640 m asl) in an 'Alfa' lattice design. Each entry was planted in two, 3-m-long beds. Agronomic data were collected on grain yield and its components, test weight, plant height, days to anthesis, and maturity. The industrial quality parameters of flour yield, protein, grain hardness, SDS sedimentation, and alveographic dough strength parameters (W) were measured. Grain samples were milled into flour using a Brabender Quadrumat Sr. Mill. Grain hardness and flour protein were determined by near-infrared reflectance and flour SDS-sedimentation. Alveographic dough strength parameter was obtained by testing 60-g flour samples following manufacturer's instructions. Mixograph mixing time and bread loaf volume were obtained using the AACC methods 54-40A and 10-09, respectively.

Agronomic performance. Agronomic data analysis revealed significant differences between the Rhino substitution lines and the Rhino control for grain yield, test weight, plant height, grain weight, and days to anthesis and maturity. The grain yield of the Rhino 6D(6A) substitutions showed significantly higher yield than the Rhino control. On average, the 6D(6A) lines yielded 0.7 T/ha above the Rhino control (7.3 versus 6.6 T/ha). These results agree with recent data from the International Triticale Yield Nurseries (ITYN) and the 1991-96 global variety release data, which suggest an adaptive advantage of complete triticale with the 6D(6A) substitution under both high and low input conditions. The 6D(6A) substitution spread into the winter triticale germplasm gene pool through 'wiinter/spring' crosses. Except for 6D(6B), which had a slightly higher test weight (77.4 kg/hl), most of the other substituted lines had similar or lower test weight when compared with the Rhino control (76.7 kg/hl). The 5D(5A) substitution lines are extremely late in maturity, because of the presence of vernalization genes from winter wheat. In contrast, the 2D(2B) substitutions are late in certain environments, because of photoperiod sensitivity. The 1D(1B) and 6D(6A) substitutions lines are shorter than the Rhino control (123 cm), but 4D(4B) is very tall (168 cm) because of the absence of the Rht2 dwarfing genes and has reduced awns. Compared to Rhino (44 g), 1,000-kernel weight of the substitution lines varied markedly from 31g for 6D(6B) to 55 g for 4D(4B).

Industrial quality. The data analysis for industrial quality parameters revealed significant differences among the Rhino substitution lines for SDS-sedimentation, grain hardness, and bread making quality parameters. Drastic increases in SDS sedimentation values in a poor quality genetic background (Rhino) and a good quality genetic background (Passi) indicate good possibilities for quality improvement in substitution lines. Athough the average SDS of the Rhino control was 5.6 ml the 1D(1B), 1D(1A), and 1D(1R) substitution lines exhibited average SDS values of 7.9, 10.0, and 10.5, respectively. Similarly, the NILs with the T1DL·1RS translocation had significantly higher SDS values (7.6 to 8.1 ml) compared with the Rhino control (5.6 ml). The availability of Glu-D1 HMW glutenin subunits 2+12 and 5+10 in 1D(1R), in addition to 1D(1B) and 1D(1A) substitutions, in the T1DL·1RS translocations improved the SDS-sedimentation values and had a significant positive effect on dough strength (ALV W), a very important characteristic closely associated with loaf volume. Grain hardness also varied among the substitution lines, ranging from hard (Rhino grain type, 40 %) in T1DL·1RS lines to soft (48-54 %) in the 2D(2R), 3D(3B), and 5D(5A) lines. However, flour yield and protein were not affected significantly in substitution lines compared to Rhino. Presently, triticales with two or more doses of Glu-D1 HMW-glutenin subunits are being developed. Once the Glu-D1 HMW-glutenins have been exploited, future research should be extended to gliadins and secalins.

Related references.

Mergoum M. 1997. Evaluation of durum wheat germplasm to root rot (Fusarium culmorum and Cochliobolus sativus) in Morocco. Plant Genetic Res Newslet 109:11-14.

Pfeiffer WH, Lukaszewski AJ, and Mergoum M. 1997. Strategies to enhance genetic grain yield potential in durum wheat and triticale. Agron Abstr.

Mergoum M and Pfeiffer WH. 1997. Agronomic performance of triticale mixtures under
contrasting moisture regimes. Agron Abstr.

Pfeiffer WH, Duveiller E, Lukaszewski AJ, and Mergoum M. 1997. The effect of single d-genome chromosome substitutions from bread wheat on spot blotch resistance on hexaploid triticale. In: Proc Inter Workshop on Helminthosporium blights of wheat (spot blotch and tan spot). 9­14 February, 1997, El Batan, Mexico (Abstract).

Mergoum M, Quick JS, Hill J, Nsarellah N, Nachit M, and Pfeiffer WH. 1997. Root rot in wheat: inoculation and screening techniques; yield loss assessment and germplasm evaluation. In: Proc Inter Workshop on Helminthosporium blights of wheat (spot blotch and tan spot). 9­14 February, 1997, El Batan, Mexico (Abstract).

El Harrak A, Mergoum M, and Saadaoui E. 1997. Major foliar diseases of triticale in Morocco. In: Proc Inter Workshop on Helminthosporium blights of wheat (spot blotch and tan spot). 9­14 February, 1997, El Batan, Mexico (Abstract).

Nsarellah N and Mergoum M. 1997. Effect of crop rotation and straw mulch inoculation on tan spot and root rot diseases in wheat. In: Proc Inter Workshop on Helminthosporium blights of wheat (spot blotch and tan spot). 9­14 February, 1997, El Batan, Mexico (Abstract).

Mergoum M and Kallida R. 1997. Le Triticale. In: Production et Utilisation des Cultures Fourrageres au Maroc (Jaritz G and Bounajmate M eds).

Inagaki MN, Pfeiffer WH, Mergoum M, Mujeeb-Kazi A, and Lukaszewski AJ. 1997. Effects of D-genome chromosomes on crossability of hexaploid triticale (X Triticosecale Wittmack) with maize. Plant Breed 116:387 389.

Ryan J, Nsarellah N, and Mergoum M. 1997. Nitrogen fertilization of durum wheat cultivars in the rainfed area of Morocco: biomass, yield and quality consideration. Cereal Res Commun 25 (1):85-90.

Pfeiffer WH and Mergoum M. 1997. Triticale: A Cropping Alternative for Marginal and stress-Prone Production Environments. In: Proc Primer Simposio Internacional de Trigo, 7­9 April, 1997, Cd Obregon , Mexico.

Sayre K, Pfeiffer WF, Mergoum M, and Varughese G. 1997. Triticale: grain yield response to input management levels. In: First All Africa Crop Science Congress, 13­17 January, 1997, Pretoria, South Africa. p. 107 (Abstract).

Some homozygous chromosome 1B or T1BL·1RS bread wheat cultivars and their BC7 near-isogenic derivatives with complementary T1BL·1RS or 1B chromosome substitutions.

A. Mujeeb-Kazi, A. Cortés, V. Rosas, M.D.H.M. William, and R. Delgado.

In our bread wheat germplasm, about 55 % of the cultivars possess the T1BL·1RS translocation. The agronomic performance of such wheats has been considered superior, and comparisons with 1B wheats have been subjects of active experiments. The comparisons include diverse T1BL·1RS vs. 1B cultivars, random F2-derived F6 lines arising from 'T1BL·1RS / 1B' cultivar crosses, and NILs using different developmental protocols. We recently produced NILs in a T1BL·1RS cultivar Seri M82 using seven backcrosses to the heterozygote followed by an ultimate selfing. The products were 'extracted' Seri lines with T1BL·1RS and Seri NILs with a chromosome 1B substitution. The parental Seri M82 cultivar formed the complete tester set to evaluate the T1BL·1RS contribution to bread wheat. Using a similar procedure, we developed a larger germplasm base to study the 1RS effect, because bread wheat varietal differences have been considered factors in diverse responses in agronomic performance. The cultivars with 1B or T1BL·1RS near isogenics are listed in Table 8 with the contributing 1B or T1BL·1RS parent identified in each entry. The final products were validated for the specific 1B or T1BL·1RS homozygous chromosome pair cytologically (Giemsa C-banding) and biochemically (GPI and A-PAGE) (See Table 4). Three plants in the cultivar Ciano 79 backcross (BC7) exhibited a C-banding polymorphism. The interstitial band of 1RS in each case was reduced markedly. After selfing the modified T1BL·1RS 1B BC7 heterozygotes, we have selected homozygous T1BL·1RS plants. These germplasms are maintained for further study.

Some durum wheat cultivars with the chromosome T1BL·1RS substituted for chromosome 1B

Mujeeb-Kazi, A. Cortés, V. Rosas, M.D.H.M. William, and R. Delgado.

T1BL·1RS germplasms of bread wheat have been used preferentially by breeders worldwide, and such cultivars are planted on over 5 million hectares. The T1BL·1RS translocation chromosome has been associated with superior agronomic performance, particularly grain yield and environmental stability. The 1RS arm also possesses four biotic stress resistance genes.

In durum wheats, the T1BL·1RS translocation has been incorporated by researchers in two cultivars ('Cando / Veery' and Altar 84). To broaden the germplasm base for evaluating T1BL·1RS contributions in different varietal backgrounds, we have now transferred T1BL·1RS to six new durums using the F1 1B, T1BL·1RS heterozygote/respective durum backcross procedure. After seven backcrosses and a selfing, T1BL·1RS homozygote derivatives were identified from each of the six cultivars (Table 5). Seed has been increased and now can be used for detailed agronomic investigations. For each cultivar, 1B homozygous types also were 'extracted'. The extracted lines will serve as the critical controls, together with the original breeders line, in further studies to evaluate the contribution of the T1BL·1RS translocation in durums.

Selections from 10 F3 bread wheat populations as a basis of the production of doubled haploids.

A. Mujeeb-Kazi, M. Inagaki, M. Van-Ginkel, R. Trethowan, R. Delgado, S. Cano, and V. Rosas.

Bread wheat breeding programs essentially require genetic recombination to occur, followed by selection of desirable recombinants and stabilization through homozygosity. Attaining homozygosity generally incorporates repeated pedigree selection or single-seed descent, but artificial production of haploid wheat plants followed by chromosome doubling has emerged as a new, quicker method for obtaining homozygous recombinant plants. This sexual process that involves 'wheat / maize' hybridization, extraction of embryos (haploids) from seed with watery or no endosperm, seedling differentiation, colchicine induced fertility restoration via doubling of the haploid chromosomal complement, and a seed increase of the doubled seed. The DH protocol also has the potential to be used in many research areas. The one presented here results in the production of homozygous DHs from breeder-selected F3 plants.

Ten F3 populations (see Table 6) were planted in El Batan, Mexico, by the CIMMYT bread wheat program. Breeders selected 100 plants in each population from which the production of at least one DH/selection was required. Total DH output was anticipated at 1,000 DHs, with 100 DHs/population. The DHs were produced across each population, seed multiplied, and biotic stress and plant-type selections incorporated. The DH yield trial is currently in progress.

Handling large numbers of DHs was facilitated by using cut tillers in a sucrose solution maintained in growth chambers. Sulfurous acid in the sucrose media controlled contamination. Hot-water emasculation was used instead of the conventional, slower hand emasculation for efficiency . Hot-water emasculation uses a water bath at 43°C and a spike treatment of precisely 3 minutes. Self seed contamination was about 1 % and could be readily identified and discarded because (a) the seed size was larger, and (b) in each case the seed had a well-formed endosperm. The DH protocol ('wheat / maize', millet, or Tripsacum) is highly effective across all wheat genotypes and plant habits (spring, winter, or facultative). Our DH output for the 10 F3 populations was 100 % effective.

Maize-mediated homozygous susceptible bread wheat/resistant synthetic hexaploid (AABBDD) derivatives resistant to Helminthosporium sativum.

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

The primary gene pool of the D-genome diploid Ae. tauschii accessions has been combined with several elite durum cultivars to yield synthetic hexaploids wheats. Screening the 620 SHs produced so far has led to the identification of some synthetics with superior resistance to spot blotch. In Mexico, conditions at Poza Rica inflict a severe of natural infection. Some of the resistant SHs were crossed with elite, but H. sativum-susceptible, bread wheat cultivars, and advanced generation populations selected for spot blotch resistance. The best bread wheat/SH derivatives formed a 50-entry advanced set with superior resistance (leaf score 9-2 or 9-3 versus 9-9 for the susceptible lines). For disease scoring, the first digit of the score indicates height of infection, where 5 = up to mid-plant and 9 = up to flag leaf; and the second digit indicates disease severity on the infected leaves, where 1 = low and 9 = total leaf destroyed.

When these lines were tested for other stresses (leaf rust, stripe rust, and Septoria tritici, at multilocational growth performance nurseries in three other Mexican locations), 18 were selected. The 10 with superior agronomic type are described in Table 7.

These F6 derivatives possessed leaf scores of 9-2 or 9-3, a seed finish rating of 2, and a spike appearance of 3. The checks were inferior in every respect (Table 7). Each of the 10 lines was crossed with maize to produce DHs. The DHs ranged from two to seven per selected derivative, were seed increased, and each DH was tested in the field for resistance scores similar to their F6 parental germplasm. These H. sativum-resistant DH lines are being distributed to 12 international locations. The homozygous base is anticipated to facilitate screening and reflect on the pathogen status across the locations. Distibuting homozygous DHs for global testing from our wide-cross program will be used for the evaluation of other stresses in the future and is being currently maximized for H. sativum wide-cross nurseries.

Resistance to Helminthosporium sativum in D-genome synthetic hexaploids and in their susceptible 'bread wheat/resistant SH' crosses.

A. Mujeeb-Kazi and R. Delgado.

Of the primary gene pool species, we have given priority to Ae. tauschii, using the T. turgidum/Ae. tauschii-derived SH route as a means of identifying resistance to biotic stresses. The resistance from these SH wheats then has been transferred to elite but susceptible bread wheat cultivars for the specific stress via bridge crosses (T. aestivum / resistant SH or the reciprocal).

From several SH wheats resistant to H. sativum in Poza Rica, Mexico, over 4 years of testing, 18 were selected for wheat improvement based upon the multiple resistance of each SH. Six are identified in Table 8. All are resistant to leaf and stripe rust. These SHs have H. sativum resistance evaluation scores of 9-2 to 9-3 for leaf damage, a score of 2 for grain, and a score of 3 for spike appearance at maturity. The advanced 'SH/bread wheat' or 'bread wheat/SH' derivatives also possess leaf and stripe rust resistance. The 10 lines listed (see Table 8) have a foliar score of 9-2 or 9-3, a grain score of 2 or 3, and a spike appearance score of 3. These advanced derivatives have been tested for 2 years. The resistant checks were BH1146, Mayoor, and Chirya, and the susceptible checks were Ciano 79 and Bacanora.

Resistance to Karnal bunt (Tilletia indica) in D-genome synthetic hexaploids and in their susceptible 'bread wheat/SH' crosses.

Mujeeb-Kazi, G. Fuentes-Davila, and R. Delgado.

The Karnal bunt disease of bread wheat kernels is caused by Tilletia indica. Though yield losses are not high or economically a major concern, a high percentage of grain infection under favorable conditions reportedly can affect grain quality. However, the disease does have international quarantine significance. We have given a high priority in testing our wheat germplasm for resistance sources, with breeding objectives to identify and transfer novel resistance genes from the alien Triticeae germplasm. Notable among these alien sources are the D-genome primary gene pool species accessions of Ae. tauschii. When combined with T. turgidum, their synthetic hexaploids exhibit less than 5 % infection. These low infection levels of the SH wheats also are expressed in their cross derivatives with susceptible bread wheats over 5 years of testing in Obregon, Mexico. These SH and 'bread wheat/SH' KB screening results are presented in Table 9 for some of the germplasms.

Septoria tritici resistance in some genetic stocks of the A, B, and D genomes and in elite susceptible bread wheat/D-genome synthetic hexaploids.

A. Mujeeb-Kazi, L.I. Gilchrist, and R. Delgado.

Triticeae species and their accessions are potent sources of genetic diversity for S. tritici resistance. This diversity resides in the primary (A and D genomes) and the secondary (B genome) gene pools. These three diploid genomes have been combined with AB genomes of several durum wheat cultivars to produce hexaploid (2n = 6x = 42) genetic stocks. These stocks are: (i) 'Durum / A genome' = AAAABB, (ii) 'Durum / B genome' = AABBBB, and (iii) 'Durum / D genome' = AABBDD. Promising screening results of some of these hexaploids are presented in Table 10 and are means over 3 years of field testing in Toluca, Mexico, using a mixture of five isolates. Some of these stocks are new and were tested only in 1997. Stocks screened and reported upon earlier were included in the recent (1997) test cycle. The disease severity was recorded using a double-digit scale at three grain-filling stages (Table 10). For improving bread wheats, several elite susceptible cultivars were crossed with resistant D-genome synthetic hexaploids and advanced conventionally using standard breeding protocols.

The A and B genome hexaploid germplasms provide the diversity that may enrich the durum wheat germplasm. These crosses of the AAAABB and AABBBB hexaploids with durums have been initiated recently. Results of the A-, B-, and D-genome hexaploid genetic stocks and D-genome hexaploid/bread wheat derivatives expressing leaf blotch resistant scores of 1-1 to 2-1 are in Table 10. The susceptible bread wheat parental checks scores were from 9-7 to 9-9.

Preliminary evaluation of alien genetic diversity suitable for scab (Fusarium graminearum) resistance.

A. Mujeeb-Kazi, L.I. Gilchrist, and R. Delgado.

Head scab of small grain cereals is a severe disease in warm and humid areas of the world. The disease adversely affects grain produced for food and feed and is diagnosed by blemished spike appearance as well as the presence of a toxin. Regions where it is encountered include Africa (Ethiopia); Asia (Iran and China); and South America (Argentina, Brazil, Paraguay, and Uruguay). In bread wheat, limited resistance has been identified and is associated with four genes. Some resistant cultivars are Frontana, Ning, and Sumai. The potential for identifying more genes in diverse alien sources ranks high and has been an area that we have started exploring in Toluca, Mexico, with germplasms derived from the annual/perennial Triticeae species of the primary, secondary, and tertiary gene pools.

Table 11. Mean Fusarium head scab infection percentages of some conventional and wide crosses of
Triticeae germplasm distributed for international testing, following observations after 35 days of artificial
inoculation in the field plantings at Atizapan, Toluca, Mexico.

Germplasm and cross number	Percentage infection mean scores *
	MV 1996	MV 1997
Sumai (Resistant check)	12.4	11.26
Frontana (Resistant check)	8.7	6.1
Mayoor // TKSN1081 / Ae. tauschii (222) ** CASS 94Y00009S-9PR-2M	5.9	5.14
Mayoor // TKSN1081 / Ae. tauschii (222) CASS 94Y00009S-13PR-1M	4.5	8.3
Mayoor // TKSN1081 / Ae. tauschii (222) CASS 94Y00009S-18PR-3M	0.2	5.3
Mayoor // TKSN1081 / Ae. tauschii (222) CASS 94Y00009S-20PR-3M	6.1	3.2
Mayoor // TKSN1081 / Ae. tauschii (222) CASS 94Y00009S-50PR-2B	0.8	4.5
Mayoor//TKSN1081/Ae. tauschii (222) CASS 94Y00009S-51PR-2B	6.3	7.6
Mayoor // TKSN1081 / Ae. tauschii (222) CASS 94Y00009S-51PR-4B	7.0	4.1
Mayoor CIGM 84.295	6.6	6.3
Bcn // Ceta / Ae. tauschii (895) CASS 94Y00194S	6.7	8.6
Turaco /5/ Chirya 3 /4/ Siren // Altar 84 / Ae. tauschii (205) /3/ 3*Buc CASS 94Y00034S	5.2	5.5
Sabuf /5/ Bcn /4/ Rabi // Gs / Cra /3/ Ae. tauschii.(190) CASS 94Y00042S	8.4	4.1
Bcn /4/ Rabi // Gs / Cra /3/ Ae. tauschii (904) CASS 94Y00162S	7.1	2.2
CS / L. racemosus//Cs/3/Pvn CIGM 81.1282-15B-2B	9.9	9.0
CS / L. racemosus //Cs/3/Pvn CIGM 81.1282-15B-3B	9.3	5.7
Seri /3/ Garza / Boy // Ae. tauschii (307) CASS 95Y00021S	7.5	---
Seri // Doy1 / Ae. tauschii (510) CASS 95Y00025S	5.9	14.8
CS /Th. curvifolium // Glenn /3/ Ald / Pvn /4/ CS / L. racemosus // 2*CS /3/ Cno79 CIGM 88.750-10PR	8.1	4.1
CS /Th. curvifolium // Glenn /3/ Ald / Pvn /4/ CS / L.racemosus // 2*CS /3/ Cno79 CIGM 88.750-4PR	5.3	10.6
Bcn /3/ 68112 / Ward // Ae. tauschii (369) CASS 94Y00125S	9.8	9.8
Altar 84 / Ae. tauschii(224) // Yaco /6/ Croc1 / Ae. tauschii (205) /5/ Br12*3 /4/.. CIGM 93.581	3.9	10.0
Turaco /5/ Chir 3 /4/ Siren // Altar 84 / Ae. tauschii(205) /3/ 3* Buc CASS 94Y00034S	8.3	10.6
Sabuf /3/ Bcn // Ceta / Ae. tauschii(895) CASS 94Y00043S	10.1	2.3
Chir 3 /5/ CS /Th. curvifolium // Glenn /3/ Ald / Pvn /4/ CS /L. racemosus // 2*CS /3/ Cno 79 CIGM 93.612	9.4	6.1
Amphiploids.
CS /Th. scirpeum (2n=10x=70)	5.8	6.2
CS /Th. elongatum (2n=8x=56)	5.5	5.1
CS /Th. bessarabicum (2n=8x=56)	6.0	5.2
Th. elongatum / Ghk (2n=8x=56)	16.8	17.7
* In 1996 five spikes were inoculated. Ten were inoculated in 1997 ** Aegilops tauschii accession number in wide crosses working collection.

Fully extruded spikes from diverse germplasms are inoculated when the anthers become visible in the central spike region. Cotton swabs soaked in the inoculum are placed by tweezers in each spike's central florets within the lemma and palea under field conditions, covered by glassine bags, and evaluated after 35 days for symptom development. Spore concentration is about 50,000. Five spikes in 1996 and 10 in 1997 per germplasm entry were treated. This led to the estimation of infection percentages of Table 11 and allowed us to form categories of germplasms showing less than 10 % and less than 20 % infection. This first cut has now formed the basis for us to distribute germplasm predominantly with up to 10 % infection for multilocational testing to researchers. The germplasm also is being assessed for stringent testing where the resistance mechanisms (Type I, II, and III) will be studied. The promising germplasm set of 29 entries including checks (Table 11) also is targeted for controlled greenhouse plus growth chamber testing. These 29 entries include intergeneric, interspecific, and conventional germplasms.

Development of a Karnal bunt (Tilletia indica) mapping population from F1 seed of Triticum aestivum cv. WL711 (susceptible)/cv. HD29 (resistant) and their reciprocal cross.

A. Mujeeb-Kazi and R. Delgado.

Producing wheat haploids by sexual crosses of 'bread wheat x maize', pearl millet or Tripsacum has become a significant procedure in wheat cytogenetics, wide crosses, and breeding. Recently, the application has been extended into genetic engineering and molecular mapping. The latter aspect formed the basis of developing a DH mapping population for Karnal bunt, where two conventional resistant and susceptible cultivars of bread wheat were utilized (Singh, personal communication). Reciprocal crosses generated 500 F1 seed/combination. The F1's were planted over several dates, emasculated, and pollinated by maize to yield enough haploid seedlings that led to the production of over 250 DHs/ combination (Table 12). These have been seed increased. The entries will be screened for Karnal bunt and utilized for molecular mapping.

WL 711 is a highly susceptible cultivar with an infection range between 50 to 100 % depending on environmental conditions. HD29 is reportedly a resistant Indian cultivar with less than 5 % infection. The DH mapping population details are in Table 12.

Publications from Wide Crosses in 1997.

Inagaki MN, Nagamine T, and Mujeeb-Kazi A. 1997. Use of pollen storage and detached-tiller culture in wheat polyhaploid production through wide crosses. Cereal Res Commun 25:7-13.

Inagaki MN, Pfeiffer WH, Mergoum M, Mujeeb-Kazi A, and Lukaszewski AJ. 1997. Effects of D-genome chromosomes on crossability of hexaploid triticale (X Triticosecale Wittmack) with maize. Plant Breed 116:387-389.

Inagaki MN and Mujeeb-Kazi A. 1997. Efficient techniques for polyhaploid production in hexaploid wheat using pearl millet crosses. In: Third Inter Triticeae Symp, 4-8 May, 1997. ICARDA, Allepo, Syria. (In press).

Inagaki MN, Varughese G, Rajaram S, Van-Ginkel M, and Mujeeb-Kazi A. 1997. Comparison of bread wheat lines selected by doubled haploid, single-seed descent and pedigree selection methods. Theor Appl Genet (Submitted).

Ma H, Singh RP, and Mujeeb-Kazi A. 1997. Resistance to stripe rust in durum wheats, A-genome diploids, and their amphiploids. Euphytica 94:279-286.

Mujeeb-Kazi A. 1997. Evolutionary relationships and gene transfer in the Triticeae. In: Third Inter Triticeae Symp, 4-8 May, 1997. ICARDA, Allep