Digitized by Kansas Correctional Industries

Thesis (Ph.D.) - University of Queensland, 2006. / Includes bibliography.

Sorghum (Sorghum bicolor [L.] Moench) is fifth among the major cereal crops in the world in terms of production area and total production. Grain sorghum can be successfully produced in a wide range of environments, its productivity is severely limited by pathogens, insects and abiotic stresses. One of these pathogens is Claviceps africana Frederickson Mantle & de Milliano, commonly known as ergot. As is the case with many sorghum diseases, the best long term approach to control ergot may be the use of genetic resistance. There is limited information about resistance to C. africana in sorghum, and the reported resistance in most lines is fertility-based. Dahlberg (1999) first reported the line IS8525 to have the most tolerance to ergot of any of the accessions screened in Puerto Rico. The specific objectives of this research are: (1) to confirm the presence of C. africana resistance in IS8525 germplasm, (2) to determine if the resistance in IS8525 is pollen mediated or ovule based, and (3) to determine if the resistance in IS8525 is heritable and stable across environments. Ergot vulnerability ratings were determined for two recombinant inbred line populations, IS8525D and IS8525J, in four locations during 2001. Also, ergot vulnerability ratings were evaluated in four test-cross populations (using as testers A3Tx623 and A3Tx623) in two locations. Evaluations of the original parents indicate that ergot tolerance in IS8525D parent was consistently better than that in IS8525J parent. As expected, neither parent provided complete resistance. The IS8525J recombinant inbred line population showed significantly more ergot susceptibility than the IS8525D recombinant inbred line population and this trend was consistent across environments. Variation for ergot vulnerability amo ng recombinant inbred lines for both populations was detected, but the amount of variability was environment dependent. In the testcross hybrids, all four populations were susceptible to ergot, primarily due to male sterility in the hybrids, confirming that the tolerance shown in IS8525 germplasm is mostly pollen mediated. However, a greater level of tolerance in the IS8525 hybrid checks confirmed the reports of tolerance by Dahlberg et al. (1998) and Reed et al. (2002).

Sorghum [Sorghum bicolor (L.) Moench] production in Africa is widespread with low yields due to low inputs and the lack of sorghum hybrids. This situation has forced most of these farmers to grow maize hybrids since they are readily available in the seed market. Sorghum hybrids could be used if their potential was demonstrated. The objective of this study is to document the level of heterosis in Southern Africa sorghum germplasm. The performance of 52 F1 grain sorghum hybrids and their parental lines was evaluated in four environments. Measurements for grain yield, panicle exsertion, days to mid anthesis and plant height were analyzed to obtain estimates of high parent heterosis. High parent heterosis was observed to be 37.18% for yield, 82.77% for exsertion, -0.02% for days to mid anthesis and 23.7% for height. ICSR-939 and (87EON366*90EON328)-LD30 can be used as testers to develop more female lines for further hybrid seed production in breeding programs because they had the highest general combining ability. Protein content averaged 11.69%. ATx635 had significantly higher protein content than ATx631 (13.49% compared to 9.69%, respectively) and its hybrids had more protein than ATx631 hybrids (11.6% compared to 10.67% for ATx631). Mean heterosis for protein content was negative at -12.5%. This shows that hybrids had lower protein content than their parents since protein content is negatively correlated to grain yield (-0.35**). Starch content averaged 72.13% and ATx631 hybrids had more starch than ATx635 hybrids (73.16 compared to 72.37% respectively). Two hybrids, ATx.631/(87EON366*90EON328)-LD30 and ATx631/ ((TAM428*SV1)*CE151)-LD3 had the highest yields (5.04 t/ha and 4.93 t/ha, respectively). These hybrids also had small grains with good hardness and acceptable whiteness. They had good exsertion, flowered in good time and had acceptable plant heights. These two hybrids were compared to regional check varieties Macia and Tegemeo for all traits and they were either superior or within an acceptable range. These two hybrids are therefore recommended for release in the region. There is need therefore to start working on the various components of seed systems in the region so that seed of these two hybrids is made available to farmers who need the seed.

Sorghum has been improved by plant breeders for yield, biotic and abiotic stress resistance, as well as quality traits by using germplasm from within the species. Interspecific hybridization can greatly increase the amount of genetic variation available to plant breeders for improvement. Interspecific hybrids between sorghum and the 19 species in the tertiary gene pool have, until recently, not been successful. The Australian species, S. macrospermum, was recently successfully hybridized with sorghum by using germplasm homozygous for the iap allele, which eliminated reproductive isolation barriers. The objectives of this research were to evaluate the potential for use of S. macrospermum in an introgression breeding program, determine the map position of the Iap locus, and backcross the iap allele into elite Texas A&M germplasm. Interspecific hybrids between S. bicolor and S. macrospermum revealed moderate levels (2.6 II per PMC) of allosyndetic recombination, indicating that introgression through genetic recombination is possible. Genomic relationships were sufficient to assign S. macrospermum the genomic formula AAB1B1YYZZ, Y and Z remain unknown. In backcrosses to S. bicolor using the female interspecific hybrid gamete and embryo rescue, BC1F1 plants were recovered. They had high chromosome numbers (2n = 35-70) and were male-sterile but three plants set backcross seed. Ninety-five percent of BC2F1 plants were 2n = 20 chromosomes and 75% of them contained S. macrospermum introgression. BC2F1 plants carried between 0-18.5% S. macrospermum introgression; in total 26% of the S. macrospermum genome was detected in the BC2 generation. Three types of introgression germplasm were created: alien addition lines; alien substitution lines; and introgression lines. Recombinant chromosomes, containing S. macrospermum introgression sites, were identified in multiple introgression lines. The Iap locus was genetically mapped to sorghum chromosome 2 (SBI-02), flanking AFLP markers were 2.1 and 2.7cM away, one AFLP marker shared the same map position (0.0cM). A genetic stock, Tx3361, was created which has iap iap genotype and improved agronomic qualities such as short plant height, white seed color, non-pigmented testa, no awns, reduced lodging, early maturity, and backcross segregation of male-sterility (ms3). This research shows that S. macrospermum is now available to plant breeders for sorghum improvement.

A wide variety of sorghum genotypes with a pigmented pericarp were grown in varying environments and were analyzed for total phenols, condensed tannins, flavan-4-ols, and in vitro antioxidant activity. In addition, sorghum flavonoids were separated, characterized, and quantified using HPLC-PDA and LC-MS. Total phenols and in vitro antioxidant activity increased when sorghums had a pigmented testa causing the presence of condensed tannins. Flavan-4-ol levels were highest in sorghums with a black pericarp (5.8-16.1 abs/mL/g), followed by those with a red pericarp (1.1-9.2 abs/mL/g). Sorghums with a black pericarp had the highest 3-deoxyanthocyanin levels (308-1885 µg/g) and these were increased when the grain had minimal weathering and was darkest in color. Sorghums with a lemon-yellow pericarp had the highest flavanone levels (260-3586 µg/g) with eriodictyol being the main flavanone. Flavanone levels were increased when the grain was bright yellow with minimum weathering and were high compared to those found in common sources (238-574 µg/g, fresh wts.). No flavonoids were predominant in sorghums with a red pericarp. Flavonoid composition varied when all sorghums were grouped by secondary plant color. Sorghums with tan secondary plant color, including those with a white pericarp, had higher levels of flavones (50-932 µg/g) than those with red/purple secondary plant color (0-172 µg/g). On the other hand, 3-deoxyanthocyanin levels were higher in red/purple plant sorghums (14-1885 µg/g) than in tan plant sorghums (0-24 µg/g). Among red/purple plant sorghums, lemon-yellow pericarp sorghums had the highest levels of flavones (51-172 µg/g). Environment and weathering had an effect on flavonoid levels. The 3-deoxyanthocyanins were reduced for sorghums grown in a dry environment (i.e. Lubbock, TX) and flavonoid levels were increased in grains with minimum weathering or molding. This study reports that all sorghums, including those with a white pericarp, have flavonoids and their levels and compositions are affected by the genotype. This information will be helpful for plant breeders, food scientists, and the pharmaceutical/nutraceutical industries in selecting sorghums with desired healthy components.

A wide variety of sorghum genotypes with a pigmented pericarp were grown in varying environments and were analyzed for total phenols, condensed tannins, flavan-4-ols, and in vitro antioxidant activity. In addition, sorghum flavonoids were separated, characterized, and quantified using HPLC-PDA and LC-MS. Total phenols and in vitro antioxidant activity increased when sorghums had a pigmented testa causing the presence of condensed tannins. Flavan-4-ol levels were highest in sorghums with a black pericarp (5.8-16.1 abs/mL/g), followed by those with a red pericarp (1.1-9.2 abs/mL/g). Sorghums with a black pericarp had the highest 3-deoxyanthocyanin levels (308-1885 µg/g) and these were increased when the grain had minimal weathering and was darkest in color. Sorghums with a lemon-yellow pericarp had the highest flavanone levels (260-3586 µg/g) with eriodictyol being the main flavanone. Flavanone levels were increased when the grain was bright yellow with minimum weathering and were high compared to those found in common sources (238-574 µg/g, fresh wts.). No flavonoids were predominant in sorghums with a red pericarp. Flavonoid composition varied when all sorghums were grouped by secondary plant color. Sorghums with tan secondary plant color, including those with a white pericarp, had higher levels of flavones (50-932 µg/g) than those with red/purple secondary plant color (0-172 µg/g). On the other hand, 3-deoxyanthocyanin levels were higher in red/purple plant sorghums (14-1885 µg/g) than in tan plant sorghums (0-24 µg/g). Among red/purple plant sorghums, lemon-yellow pericarp sorghums had the highest levels of flavones (51-172 µg/g). Environment and weathering had an effect on flavonoid levels. The 3-deoxyanthocyanins were reduced for sorghums grown in a dry environment (i.e. Lubbock, TX) and flavonoid levels were increased in grains with minimum weathering or molding. This study reports that all sorghums, including those with a white pericarp, have flavonoids and their levels and compositions are affected by the genotype. This information will be helpful for plant breeders, food scientists, and the pharmaceutical/nutraceutical industries in selecting sorghums with desired healthy components.

Brown flaxseed hulls were added to de-germed corn meal and processed into extrudates with acceptable texture and increased nutritional benefits. The addition of brown flaxseed hulls to a corn based expanded snack increases the dietary fiber, alpha omega 3 fatty acids, and antioxidants levels. The addition of flaxseed hulls to a corn based snack can increase its susceptibility to oxidative rancidity which can limit shelf life. Whole ground tannin sorghum with added brown flaxseed hulls was processed into extrudates and texture, antioxidant activity, and stability were evaluated. Brown flaxseed hulls were mixed with de-germed yellow corn meal in ratios of 0:100, 15:85, 20:80, and 25:75 (w/w) and extruded with 12 and 15% feed moistures using a twin screw extruder to produce direct expanded extrudates. Expansion of extrudates containing brown hulls decreased as the amount of hulls increased. Dried extrudates had acceptable flavor immediately after processing. Total phenols and antioxidant activity of extrudates containing 20 and 25% brown flaxseed hulls, extruded at 15% feed moisture were higher than de-germed corn meal extruded at 16% feed moisture. Brown flaxseed hulls were added at 20% to whole ground white and sumac (tannin) sorghums and processed into extrudates. Expansion increased for sorghum extrudates containing brown flaxseed hulls. The addition of brown flaxseed hulls increased antioxidant activity and total phenols of both white and sumac (tannin) extrudates. The sumac (tannin) extrudates had the longest delay in producing off odor (paintlike odor) and had the lowest p-Anisidine values compared to white (ATX631x RTX 436) sorghum and corn meal with added flaxseed hulls. Corn meal extrudates with 20% brown flaxseed hulls produce off odors more rapidly than other extrudates. This suggests that the tannins in sorghum maybe extending shelf life because of their antioxidant activity. The addition of brown flaxseed hulls can be used to increase nutritional value and antioxidant levels in a direct expanded product. Also the use of tannins sorghums in products containing flaxseed may help delay oxidation, thus preventing the occurrence of off odors. Further work needs to be done to verify results.

Sorghum has been improved by plant breeders for yield, biotic and abiotic stress resistance, as well as quality traits by using germplasm from within the species. Interspecific hybridization can greatly increase the amount of genetic variation available to plant breeders for improvement. Interspecific hybrids between sorghum and the 19 species in the tertiary gene pool have, until recently, not been successful. The Australian species, S. macrospermum, was recently successfully hybridized with sorghum by using germplasm homozygous for the iap allele, which eliminated reproductive isolation barriers. The objectives of this research were to evaluate the potential for use of S. macrospermum in an introgression breeding program, determine the map position of the Iap locus, and backcross the iap allele into elite Texas A&M germplasm. Interspecific hybrids between S. bicolor and S. macrospermum revealed moderate levels (2.6 II per PMC) of allosyndetic recombination, indicating that introgression through genetic recombination is possible. Genomic relationships were sufficient to assign S. macrospermum the genomic formula AAB1B1YYZZ, Y and Z remain unknown. In backcrosses to S. bicolor using the female interspecific hybrid gamete and embryo rescue, BC1F1 plants were recovered. They had high chromosome numbers (2n = 35-70) and were male-sterile but three plants set backcross seed. Ninety-five percent of BC2F1 plants were 2n = 20 chromosomes and 75% of them contained S. macrospermum introgression. BC2F1 plants carried between 0-18.5% S. macrospermum introgression; in total 26% of the S. macrospermum genome was detected in the BC2 generation. Three types of introgression germplasm were created: alien addition lines; alien substitution lines; and introgression lines. Recombinant chromosomes, containing S. macrospermum introgression sites, were identified in multiple introgression lines. The Iap locus was genetically mapped to sorghum chromosome 2 (SBI-02), flanking AFLP markers were 2.1 and 2.7cM away, one AFLP marker shared the same map position (0.0cM). A genetic stock, Tx3361, was created which has iap iap genotype and improved agronomic qualities such as short plant height, white seed color, non-pigmented testa, no awns, reduced lodging, early maturity, and backcross segregation of male-sterility (ms3). This research shows that S. macrospermum is now available to plant breeders for sorghum improvement.

Sorghum (Sorghum bicolor [L.] Moench) is the fifth most economically important cereal grown worldwide and is a source of food, feed, fiber and fuel. Sorghum, a C4 grass and a close relative to sugarcane, is adapted to hot, dry adverse environments. Some genotypes of sorghum called stay-green have delayed leaf senescence during grain ripening under drought stress conditions which allows normal grain filling whereas most sorghum lines senesce early under post-anthesis drought. Eight sources of stay-green have been identified in the sorghum germplasm collection, most originating from Sudan and Ethiopia. The diversity of the eight sources of staygreen was analyzed using 55 simple sequence repeats (SSR) markers with genome coverage. This analysis showed that the sources of stay-green are quite diverse and can be divided into five groups based on race or working group. Three sources of stay-green have been used to identify 12 major quantitative trait loci (QTL) that modulate this trait. The origin of favorable alleles for stay-green was traced backward to ancestral lines and forward into breeding materials derived from stay-green germplasm. The analysis of the origin of favorable alleles for stay-green helped explain why subsets of stay-green QTL were identified in different studies and provided evidence that there may be more than one favorable allele in the sorghum germplasm for several of the stay-green QTL. Analysis of stay-green breeding lines from three public sorghum-breeding programs revealed that one of the main QTL identified in mapping studies was not being used in the breeding programs (0/13), most likely due to its association with an allele for lemon yellow seeds. In addition, a subset of the regions containing favorable alleles for staygreen from the genotype BTx642 were over represented in stay-green breeding lines. Nearly isogenic lines containing favorable alleles from BTx642 for Stg1, Stg2, Stg3, and Stg4 in a RTx7000 (senescent) background were characterized and each NIL was shown to exhibit a stay-green phenotype. Based in part on this information, fine-mapping of Stg1 was undertaken by crossing the Stg1 NIL to RTx7000. Overall, these results revealed the origin of favorable alleles for stay-green and the current utilization of alleles for stay-green in public breeding programs. In addition, this study identified additional stay-green sources that could be used for further QTL analysis and highlighted the genetic complexity of the stay-green trait.