DEVELOPMENT OF STRESS RESISTANT/HIGH YIELD SORGHUM GERMPLASM FOR RELEASE AND USE IN INVESTIGATION OF CONTRIBUTING PHYSIOLOGICAL MECHANISMS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0196756
• Project Start Date: Jun 1, 2003
• Project End Date: May 30, 2008
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF NEBRASKA
(N/A)
LINCOLN,NE 68583

Performing Department
AGRONOMY & HORTICULTURE

Non Technical Summary
Variable Great Plains environments give dryland crops ranging from near irrigated levels to failures. Limited progress has been made in screening for producing high yield/stress resistant sorghums (15 to 25 bu/A above commercial hybrids). The purpose of this research is to continue improving sorghum yields in both favorable and stress environments by (1) improving population pools with high yield/stress resistant germplasm and (2) to improve our biochemical knowledge of stress resistance and high yield to enhance yield improvement rates.

Animal Health Component

40%

Research Effort Categories

Basic

20%

Applied

40%

Developmental

40%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
111	1520	1000	25%
203	1520	1020	50%
206	2499	1080	25%

Knowledge Area
206 - Basic Plant Biology; 111 - Conservation and Efficient Use of Water; 203 - Plant Biological Efficiency and Abiotic Stresses Affecting Plants;

Subject Of Investigation
1520 - Grain sorghum; 2499 - Plant research, general;

Field Of Science
1000 - Biochemistry and biophysics; 1080 - Genetics; 1020 - Physiology;

Keywords

sorghum

mitochondria

water use efficiency

stress tolerance

crop yields

mechanism of action

carbon

color

germplasm

plant genetics

repositories

plant physiology

seed size

seed weight

linkage (genetics)

preservation

seed storage

heterosis

mode of inheritance

plant biochemistry

Goals / Objectives
Two overall objectives are (1) to continue development of broad based tan plant populations and test selected lines for stress resistance and high yield for agronomic tan plant gene storage and industry use and (2) use lines developed to research probable developmental and metabolic trait explanations of their stress resistance and high yield potential. OBJECTIVE 1: (a) Continue random mating, testing and selection of one B reaction tan plant sorghum population with high yield potential. (b) Release one broad based seed size population (NSSC6) as a variable seed weight gene preservation and a breeder utilization population. (c) Continue random mating for three to five additional years to further break down apparent linkages between seed weight control genes and genes controlling agronomic traits such as height, maturity, leaf width seed number, etc. for a second release. This will be a more agronomic germplasm pool to improve breeder selection efficiency but could have a narrower genetic base than in NSSC6 in objective (b) above because of selection. Reducing height can increase seed number due to less vegetative/floral competition before anthesis which in turn will often translate into greater numbers of smaller seeds. However, when selected lines are put into hybrid combination the progeny hybrids may express simultaneous heterosis for seed number and seed weight to augment seed weight as is the case in our high yield/stress resistant W x N312R hybrid. (d) Test pollinator selections from the NSSC6 seed size population (1b above) for yield and simultaneous heterosis for seed weight and seed number. Release lines as appropriate from NE testing at the Mead UNL Experiment Station Farm, Havelock, Ruskin, NE and Nebraska Outstate Testing in NE. Commercial testing is also being done in KS and TX. (e) Characterize the inheritances of the seed weight and seed number components of yield in terms of male and female contributions. OBJECTIVE 2. (a) Conduct simultaneous dark CO2 evolution and O2 consumption measurements on whole sorghum plants in the dark to expand ideas about carbon economy in both stressed and high yield plants. Perhaps ratios of O2 consumption to CO2 evolution will expose something about conservation of dark respiratory CO2 via recycling in plant dark reaction systems when the demand for CO2 is high in stressed plants as partially closed stomata limit CO2 availability in the light. Also even though photosynthesis may be high under high growth/high yield conditions, CO2 demand for growth may be high enough that the CO2 supply for providing carbon skeletons for mitochondrial coupled both maintenance and growth syntheses is marginal or deficient. (b) New mitochondrial research will be developed based on efficiency of ADP oxidative phosphorylation described in Fig. 1 and on results obtained in Obj. 2(a). (c) Evaluate grain fill duration in relation to seed weight, seed number and yield. (d) Attempt manipulation of grain fill duration by chemicals which may delay embryo maturation.

Project Methods
Objectives follow in the order given in section AD-416. Objective 1: (a) Randomly mating all sorghum populations (B or R) is accomplished by random selection of generally 200 to 400 sterile panicles and compositing equal seed numbers from each panicle. (b) Releases are made from collections described in (a) above. (c) Random mating is the same as in (a) above but selection is for traits indicated, mainly reduced height, seed weight, seed number and medium to small leaves. (d) Pollinator selections are lined out at the S2 stage with continued selection for uniformity with hybrid testing beginning on S4 lines. (e) Maternal and cytoplasmic effects will be estimated from reciprocal crosses made between two contrasting seed weight A/B line pairs (2.2 and 3.0 g/100 seeds) and random population S1 plant selections to obtain reciprocal F1, F2 and backcross generations to get needed generations. The A line version is sterile and the B is fertile. Random population steriles and fertiles are used to make crosses with the two respective A and B lines. Objective 2: (a) Closed chambers will be used to simultaneously monitor O2 uptake (using an O2 electrode and CO2 evolution using an infrared gas analyzer) to gather information specified in Obj. 2a above. (b) Standard oxygen electrode mitochondrial measurements are used for O2 consumption estimates. (c) Grain fill durations are assessed by bloom dates and kernel black layer dates. (d) Chemical introduction into seeds will be attempted by phloem feeding or kernel surface entry.

Progress 06/01/03 to 05/30/08

Outputs
Project terminated 12/31/05. Faculty member has retired.

Impacts
No further progress to report due to retirement of Dr. Jerry Eastin.

Publications

• No publications reported this period

Progress 10/01/03 to 09/30/04

Outputs
Gerplasm Improvement Objective 1: (a) The planned random mating of a stress resistant/high yield B population was accomplished by selecting and recombining 200 plus sterile heads randomly pollinated within the population. One additional random mating will be selected before release. (b) about 150 selections within the population will be carried to F4 status and submitted for release. (c) A broad based moderately larger seed size, high seed number population (NSSC6) population was random mated and selected for about three more random matings before release. The goal is to improve seed size without reducing seed number and hence increase yield in combine height sorghums. The mechanism for improvement may be through breaking apparent height/maturity linkages which may allow selection for longer grain fill to improve seed weight in high seed number lines to achieve higher yields. (c) One line release in 2005 will be requested from germplasm development as in (b) above based on 2003 NE Outstate Test data from Dr. Lenis Nelson and other tests. Additional releases will be considered from 2004 NE Outstate Tests. (d) Hybrids from 2004 nursery crosses and the 2005/5 winter nursery will be tested in 2005 for line releases. Physiological mechanism research objectives have been very limited due to loss of technician help. However, simultaneous monitoring of respiratory CO2 evolution and oxygen consumption will be attempted in 2005 to see if that process can be used to expose potential relationships between carbon dioxide recycling and stress resistances and/or yield potential differences in crop plants.

Impacts
Based on past NE Outstate Test Data releases from this project (notably N312R based hybrids), pollinators from this program show an advantage of $5,000,000 to $14,000,00 advantage to NE farmers if used on 200,000 acres.

Publications

• None in 2004. Publication and further release submissions will be made in 2005/6

Progress 10/01/02 to 09/30/03

Outputs
Sorghum improvements are being realized via high yield/stress resistant randomly mated R and B population developments from which R and B lines are developed and tested for release to commercial breeders. Hybrid tests to date have been primarily for UNL R line testing and release. Most B line selections have not been male sterilized for testing in hybrid combinations. Past R line performances are illustrated from the 1999-2001 NE Outstate Tests conducted by Dr. L. Nelson. Our best hybrid, Wheatland x N312R, averaged 136.5 bu/A in 7 dryland tests over three years for a 15.5 bu/A advantage over the top commercial hybrid (DK53) and 22.5 bu/A over the mean of the top four commercial hybrid average for about $35 and $50 per acre advantages, respectively. These comparative performances are a consequences of a water/heat stress screening program exercised at Garden City, KS, some 25 years ago. Results from the next generation of R lines developed (tan vs purple pigmented plants to enhance both marketability and yields) are likewise encouraging. The Nebraska 2003 Outstate Test for Gage County had three hybrids (TX631 X G60120-1, TX631 X N580R and N581R) ranked first, third and tie for 4th at 145.5bu/A, 141.6 bu/A and 141.6 bu/A, respectively. Seven other hybrids from Dekalb, Garst Pioneer, Sorghum Partners and Monsanto in addition to our three UNL hybrids placed above the LSD05 cut off yield level of 130.2 bu/A. The Test mean was 121.3 bu/A. Results alluded to in the independent NE Outstate Tests plus many similar project test results are a consequence of determining the most sensitive growth stages relating to yield components (mostly by temperature treatments for precision control), fashioning a field stress screening technique by water stressing plants near the most sensitive stages(near microsporogenesis) and field stress pressuring up to 900 S3 high yield population derivatives. And selecting superior stress resistant entries they are both recycled in a population and lined out to be tested in hybrid combination as above. The populations serve as gene banks for stress resistant production genotype traits and will be useful for decades. Both line releases and population gene banks are useful to commercial breeders. During the course of these investigations we also learned that simultaneous heterosis exists for both the seed number and seed weight components of yield

Impacts
The 1999-2001 three year data set gives the best estimate of economic impact. Nebraska has about 600,000 acres of sorghum in 2003 of which Wheatland X N312R is probably adapted to about 400,000 acres. A $35/A advantage would put about $14.000,000 extra in the pockets of producers. A comparative figure for the $50/A advantage over the mean of the top four commercial hybrids would be on the order of $20,000,000 more for producers. Grain handlers, farm suppliers and consumers likely would also benefit from greater and more efficient production.

Publications

• Three Experiment Station Releases have been approved internally (2003) but changes in release policy development to allow licensing are delaying public release and registration in Crop Science.