Pioneer Sorghum Research
By Roger Monk
The goal of the Pioneer Sorghum Research Department is to utilize the science of genetics to improve the profitability of sorghum customers. Pioneer’s sorghum research group represents the first step in the Pioneer commitment to sorghum growers. Researchers develop the elite grain sorghum hybrids Pioneer produces, sells and services. Pioneer strives to ensure that the most well adapted, high quality sorghum hybrids are properly positioned with every customer.
Pioneer sorghum research is worldwide in scope, yet keenly aware that local adaptation is the key to success. Pioneer’s sorghum research group utilizes 3 research stations in the United States and 6 additional stations in sorghum growing regions around the world to develop elite inbred lines and hybrids. Each station is located in an environment where disease, insect or climatic constraints can be evaluated. By screening hybrids repeatedly against yield limiting conditions, products are developed that are dependable and profitable year after year. Pioneer sorghum breeders annually evaluate over 100,000 yield plots at approximately 60 testing locations in four countries. In addition to hybrid testing, over 200,000 individual rows are grown for selection in breeding nurseries for inbred development programs.
Market Segments Within Major Countries
|U.S. - East Kansas||red, white - mid early - late maturity|
|U.S. - High Plains||red, white - mid early - mid late (dryland & irrigated)|
|U.S. - South and Central Texas||red - mid early-late|
|Mexico - Tamaulipas||red - medium to late - similar to South Texas|
|Mexico - Bajio||red, brown - early, mid early to late|
|Australia - Central/Western Downs||red - mid early to mid maturity|
|Australia - Central Queensland (CQ)||red - mid early to mid maturity|
|Australia - Northern New South Wales (NSW)||red - mid early to mid late maturity|
|Brazil - Central Brazil (Safrina)||red-mid early to mid maturity|
|Brazil - Southern Brazil||red, brown - mid late to late (like Argentina)|
|Venezuela - Guarico Area||red, brown, white - mid late to late|
|Portuguesa Area||red, brown - mid to mid late|
|Colombia - Tolima Valley||red, white - mid early to mid|
|Cali Valley||red, white - mid to mid late|
|Humid Caribbean||brown - mid late to late|
|Italy||white - very early to early|
|Spain||red, mid early to mid - (Use U.S. hybrids)|
|Thailand||red - mid late - (Use Australian hybrids)|
|Central America - Guatemala, Nicaragua,
Panama, Belize, Dominican. Rep.
|Use hybrids from U.S., Mexico or S. America|
|Egypt||Sorghum sundangrass only|
Pioneer Sorghum Breeding Locations
Pioneer’s director of sorghum research, Dr. Kay Porter, leads the sorghum research efforts from Plainview, Texas. Plainview is located in the heart of the sorghum hybrid production area in the United States. Dr. Porter travels extensively, coordinating the movement of germplasm among the global sorghum research centers and monitoring the commercialization of products.
Figure 1: Pioneer North American Sorghum Research Stations.
The research program at Plainview, Texas focuses on developing hybrids adapted to dryland production areas of the High Plains and western Kansas. Yield, standability and drought resistance are key traits for this station. The Plainview station also maintains over 15,000 accessions representing historical and potential genetic diversity for use by Pioneer sorghum breeders. In another part of the program, photoperiod sensitive, exotic germplasm is incorporated into adapted types through a conversion process to make non-adapted genetic material useful in temperate climates.
The Manhattan, Kansas, station develops hybrids for sorghum growers in Nebraska, Kansas Oklahoma, southern Illinois and eastern Missouri. Working on a full range of maturities creates unique possibilities and an opportunity to incorporate a wide range of germplasm. In this area, where the length of the growing season can change significantly each year, seedling vigor is important for early growth and rapid drydown is favored for fall harvest. With a goal of maximizing harvestable yield, the station addresses the yield limiting factors of greenbug, sooty stripe, Fusarium stalk rot and post-freeze lodging in their development and testing programs.
The Taft, Texas research station is responsible for developing hybrids for the southern United States and northern Mexico. The variable rainfall pattern at the Taft station ensures environmental diversity across years, where drought is a constant reality. In addition to yield tests and selection nurseries, the Taft station also conducts disease-screening nurseries for anthracnose, head smut and downy mildew. A second part of the effort is devoted to identifying and incorporating new disease tolerant,yield enhancing germplasm into elite materials for hybrid development.
The sorghum research team in North America utilizes winter nursery sites in Puerto Rico, Mexico and Chile to augment the breeding process. Winter nurseries allow Pioneer sorghum research scientists to grow two or three generations a year to increase the speed of genetic advances.
Research centers located in Australia and Mexico develop hybrids uniquely suited to the environments in those countries. The breadth and coordination of Pioneer’s research program ensures that elite genetic combinations are available to maximize sorghum profitability for our customers.
Figure 2: Taking notes on the grain sorghum material at the Puerto Vallarta winter nursery, Mexico.
Steps in Hybrid Development
Early in the 20th century, plant scientists discovered a hybrid produced by crossing 2 unrelated inbred lines often showed heterosis, or increased vigor, when compared to the parental lines. In grasses, this vigor was expressed by more rapid growth, larger plants and significantly higher seed yields. Developing hybrids to capitalize on heterosis was straightforward in corn where a hybrid could be produced by detasseling a line to create a seed parent. However, crops like sorghum, where both male and female parts are in the same floret, awaited the discovery of cytoplasmic-male sterility to produce a system for economical hybrid seed production. Sorghum hybrids became widely available during the 1950s (Quinby, 1974).
Initially, the lines used as parents were widely adapted varieties grown across the Plains, such as Wheatland, Combine Kafir-60, Hegari and Martin. As the crop became more widely grown, diseases and insects that had been minor problems became more widespread. Plant breeders have been able to incorporate genetic host-plant resistance to a number of pathogens and pests. The difficulty with this approach is that pathogens continue to evolve and occasionally outbreaks of a new biotype or pathotype occur. Some problems, such as midge tolerance and drought tolerance can be multigenic or recessive in inheritance. Thus, the breeding strategies required to deal with the evolving growing environment are more complex, and the progress made through plant breeding can be less dramatic today, when compared to the early days of sorghum improvement.
A typical breeding project begins with the identification of a deficiency in the current product portfolio or an anticipated need. A Pioneer sorghum research scientist considers the combinations that can be made using existing inbred lines to determine if the problem can be solved in a short timeframe. If not, a process of creating segregating populations, selecting within those populations for maturity and adaptation, purifying the selections and combining them to produce new hybrids for testing is necessary. A Pioneer sorghum research station will have hundreds of selections at each step along the way, utilizing increasingly stringent selection criteria for each generation.
With each generation of self-pollination, an inbred line becomes more uniform. After 3 or 4 generations, a line that will be a male pollinator row (R-line) is ready to be tested for combining ability by crossing to an elite female (A-line). The reciprocal operation involves testing for a new A-line by crossing to an elite R-line. However, lines that will become new females must first be crossed to a cytoplasmic-male sterility source and back-crossed several times to produce a new sterile line. This process adds at least 2 years to the development time of new sorghum seed production females.
Usually, several hundred new early generation lines are crossed each year. Within the Pioneer system, all of these hybrids are initially yield tested at 2 or 3 locations. In any given year, 20-25 percent of these lines are selected for advancement. The program continues by crossing the selected lines to several elite lines and testing these hybrids. This process of elite selection continues for at least 4 years, with each advancing year becoming a more stringent test (i.e., more replications, more locations, and tougher competition). Hybrids that lodge, succumb to disease, or have poor agronomic characteristics are discarded. Only after a hybrid has been developed this far, does the research group propose it for commercialization. If sales and marketing groups agree the new hybrid adds significant value to the product line, it will be assigned an experimental number and seed produced in limited quantities. Newly advanced hybrids are grown in strip trials (PAT) across a wide range of conditions for additional verification.
The key goal of Pioneer sorghum researchers is to produce more harvestable grain yield;, they must also be constantly aware of yield-limiting problems such as disease, lodging and insect damage. While new hybrids and lines are moving through the yield trial system, these new hybrids are also being evaluated for disease and insect resistance in targeted screening locations. This dual approach of maximizing yield along with defensive traits identifies high-yielding hybrids with as many needed traits as possible to help improve sorghum profitability for our customers.
New techniques involving molecular technology and information management are increasing the efficiency of the sorghum breeding program. The development of molecular markers for disease tolerance traits allows the identification of resistant genotypes while reducing the expense and errors associated with field screening. By fingerprinting diverse lines with an array of molecular markers, it is possible to discern genetic relationships and optimize the chance to develop superior combinations. New statistical tools are also being developed that will combine molecular information with pedigree and trait information to further enhance breeding strategies. All of these new technologies will help Pioneer sorghum research lead the industry in the development of superior products for today and into the future.
Roger Monk earned a doctoral degree in plant breeding from Texas A&M University. He currently serves as a Pioneer research scientist, leading a team responsible for developing sorghum hybrids for southern United States and northern Mexico. He has been with Pioneer Hi-Bred since 1996.
Quinby, J.R. 1974. Sorghum improvement and the genetics of growth. Texas A&M University Press. College Station, Texas.