Hybrid Wheat Workshop

August 4, 1998

Moderator: Dr. Ian B. Edwards, Pioneer Hi-Bred International, Inc.

Dr. Koji Murai

Dr. Murai described the two-line hybrid wheat production system his group has been working on for approximately 10 years. It is based on Aegilops crassa Cytoplasm in which pistiloidy is induced when grown in environments with day lengths of less than 15 hours.

They have found a number of local varieties (e.g. Norin 20) to be male sterile when backcrossed into Ae. Crassa cyto. From some genetic studies they have found Chinese Spring has a dominant restorer gene (Rfd1) on 7DL, there are several modifiers present as well. When backcrossed into Ae. Crass, Norin 61 was found to have multiple restorer genes, probably 4. Due to the photoperiod impact of the crassa cytoplasm, these restorer genes are needed only to grow the hybrids in areas with day lengths longer than 15 hours.

Hybrid seed purity was relatively low in the hybrids they have checked, ranging from 48-72%. Even with this low level of hybrid seed they found heterosis levels as high as 40% over the best parent and 13% over the best commercial variety. They observed no deleterious effect of the Ae. Crassa cytoplasm.

This hybrid production system is patented by Sumitomo Chemical Company.

Mr. Tony Worland

Mr. Worland described some of the work done with combinations of Rht alleles (rht, 1, 2, and 3), their influence on height and productivity. He produced NIL in Maris Huntsman, Maris Widgeon, and April Bearded with Rht combinations rht, 1, 2, 3, 1+2 and 2+3. Hybrids that contained 3 dwarfing alleles produced the highest yield by having greater number of kernels/spike. In general, the highest yields were from hybrids with heights of about 90 cm.

Other comments - hybrids with Rht 3 produced some high yields but they tended to interact strongly with the environment especially in parts of Eastern Europe. Hybrids with Rht 8 or 9 were thought to be more useful in those environments.

Dr. Yang Yen

Dr. Yen described some patented work of Wengui Yan, a USDA rice breeder located at Stuttgart, AR. The work involved the incorporation of a herbicide resistance gene into the male parent of the hybrid. He proposed to spray the herbicide on the F1 in farmer's field to kill any plants resulting from selfed seed. It was felt that this would help hybrid purity problem in growers' fields.

Dr. Kim Kidwell

Spring wheats in Washington are not favored because of lower yield potential. Kim is interested in hybrids, specifically spring X winter hybrids, for use in both replant of winterkill areas and normal seeding situations. With the help of Hybritech, they are producing a set of 56 hybrids involving four soft white winter and four soft white spring parents, the set will include the reciprocals. This set will include 12 spring X spring and winter X winter hybrids and 32 spring X winter hybrids. She plans to look at yield and other agronomic traits, and end use quality. She also will look at DNA diversity and yield level, markers that may be associated with agronomic traits, and use AFLP's to check diversity of non-methylated regions. Intra- and inter growth habit hybrids also will be compared.

Other comments: In Argentina semi winter X spring wheat hybrids have been the highest yielding types.

Dr. Mike Winzeler

Dr. Winzeler described the approach his group at the Swiss government institute used in their hybrid development work. They were primarily interested in combining resistance to the seven fungal pathogens they felt were important and high end use quality.

Their program began in 1985 and the production system was based on a Ciba developed CHA. The availability of the CHA ended with the formation of Novartis. Since 1997 they have worked with Hybrinova and with the Ae. Variabilis system with 1B/1R.

Over the years they have found: disease resistance (leaf and stripe rust) that is controlled by dominant genes is readily incorporated into hybrids via one parent. Resistance to Septoria, powdery mildew, and other controlled by additive genes exhibit negative heterosis that suggests both parents must have good levels of resistance in order for the hybrid to be resistant. The same was true for the end use quality traits they measured, Zeleny and protein percent. The hybrids tend toward midparent for both these traits. Heterosis levels of 5-12% best parent and 2-5% best pure line were common to their hybrids. They have found hybrids between winterhardy spring wheat (facultative?) X winter wheat to yield very well.

Other comments - although they have little experience with the Ae. Variabilis system, they observed fertility restoration problems (<50%) in those they have tried.

Dr. Peter Wilson

Dr. Wilson provided some information about their hybrid program and discussed some of the challenges they face in marketing hybrids in Australia.

Their hybrid system is based on the timopheevi CMS from the old Cargill program. Some facts he provided were: grower payment to produce hybrid seed - US $240/ton.

Ave. yield/female acre - 3.5 ton/ha

Ave. yield/total area - 2.1 ton/ha

Ratio female:male - 60:40 occasionally 70:30

Hybrid seed selling price - US$600/ton, are bulk discounts

Ave. seeding rate - 20-70 kg/ha

Farm saved seed on pure lines - >85%

Australian wheat area - 9 x 10⁶ ha

Ave. yield - 1.6 ton/ha

Yield range - 0-7 ton/ha

Ave. pure line seed cost - US$200-300/ton

Issues they have to deal with in Australia are as follows:

Best hybrids have 10-12% yield advantage over best varieties, they have found it very difficult to go higher on a consistent basis. The hybrids have a higher G X E response, which makes growers nervous. Over time hybrids maintain their advantage though it may slip to 3-5% in some years. Seed production costs are a major variable in profitability of hybrids. They have used strong selection pressure for crossability (female) and pollen production to help. They have experimented with mechanical assistance for pollen movement and have done some work with female/male blends for hybrid production. They have worked on combining ability patterns with some success partly due to having to maintain separate female and restorer breeding programs.

Dr. Zhonghu He

Dr. He described some of the hybrid work that has been done in China. The area planted to hybrids has gone down the last several years from about 20,000 has to 2,000 has primarily due to farmer dissatisfaction with the product they receive. Growers complain about poor hybrid seed quality, that current pure lines are equal to or yield more than hybrids, and that high seeding rates make hybrids too costly to use.

Over the years several genetic and chemical hybrid production systems have been tried. The timopheevi CMS system was started in 1965 and the T. kotchshyi and Ae. Ventricosa were initiated in 1987. More recently they have used the two line method (short day/low temperature system from Hunan Agr. Univ.) as well as two different CHA. The CHA were from Monsanto and one locally developed at Tianju Academy (Sc2053). Average seed set in hybrid production fields in the 30-50% range although in 1998 was near 70%.

Dr. Srbislav Dencic

Dr. Dencic described some of his work involving hybrids in which one parent is multifloret or branched habit. He did not describe a hybrid production system other than to say all the work was done by hand. Since he used the branched or multifloret type as the female, I hope he had a very efficient emasculation or sterilization method. His yield data was based on multiple single row plots but he observed up to 30% yield advantage in hybrids involving branched type females and 10-12% in hybrids with multifloret females. The F1 plants with a branched parent were somewhat branched but not to the same extent as the female.