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 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.

Symbioses between cool-season grasses (Subfamily Pooideae) and endophytic fungi in the genera Epichlo and Neotyphodium straddle a continuum of interactions from antagonistic to highly mutualistic. Although these two genera of endophytes are closely related, Neotyphodium endophytes are strictly seed-transmitted and provide many physiological and defensive benefits to their hosts, while Epichlo spp. have an obligately sexual contagious stage wherein host inflorescences are replaced by fungal sexual structures (stromata), effectively sterilizing the plant. Between these two extremes of interactions are Epichlo spp. with a mixed strategy, where some grass tillers are sterilized while others develop normally and yield healthy endophyte-infected seeds. These symbioses offer a unique opportunity to dissect evolutionary mechanisms that may drive movement along this continuum. The research presented characterizes distinct hybridization processes in endophytes and grasses that result in the generation of astounding genetic diversity for the symbiosis. Interspecific hybridization via hyphal anatomosis is a common feature of Neotyphodium endophytes, and may promote mutualism by combining suites of defensive alkaloid genes and ameliorating the adverse evolutionary effects of an asexual lifestyle. My results demonstrate that several genetically distinct hybrid endophytes infect grass species in tribe Poeae. Further, I show that a highly mutualistic asexual endophyte infecting tall fescue (=Festuca arundinaceum Schreb.), Neotyphodium coenophialum, also infects two closely related and interfertile relatives of this host. My findings suggest that this seed-borne endophyte may have been introgressed into these grasses through sexual grass hybridization events. These findings highlight interspecific hybridization as a means of generating tremendous genetic variability in both endophytes and their hosts, thus magnifying the adaptive evolutionary potential of these symbioses. Further, I establish a phylogenetic framework for grasses naturally harboring Epichlo and Neotyphodium endophytes. I show that patterns of genetic divergence among grass lineages are emulated by those of their fungal symbionts. These results suggest that endophytes have co-evolved with grasses in subfamily Pooideae, and may have played a critical role in the evolutionary success and radiation of this group of grasses.

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18826号 / 理博第4084号 / 新制||理||1587(附属図書館) / 31777 / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 曽田 貞滋, 准教授 渡辺 勝敏, 教授 高橋 淑子 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

In order to reduce their predation risk, species have evolved a range of anti-predator behaviours. One co-ordinated anti-predator behaviour present in some group-living species is sentinel behaviour. In this behaviour individuals take up an elevated position and scan for threats, providing an alarm when one is spotted. However, this behaviour can lead to social conflict. Sentinel behaviour is a public good, i.e. the benefits are felt by all group members, but the costs only accrue to the actor. Thus it may be open to free loading, requiring individuals to monitor collaborators to prevent cheats. Additionally, individuals may vary in their alarm call reliability, which may select individuals to alter their behaviour based on caller ID. Monitoring others requires individuals to be closely associated, yet individuals may be spread out. For instance, foraging groups may be some distance from their nest, yet nestlings are particularly vulnerable. Adults should reduce their number of nest visits if a threat is nearby, so individuals returning from the nest may be selected to communicate about any perceived threats. Additionally, when perceiving threats, species need not use only conspecific information, because heterospecifics can also provide relevant information. In this thesis, I test these ideas in the Southern Pied Babbler (Turdoides bicolor), and I show that a) pied babblers monitor the quantity and quality of group-mates’ anti-predator behaviour; b) babblers accompany naïve sentinels and I investigate whether this may be related to anti-predator teaching; c) babblers do not appear to actively communicate about perceived nest threats because they do not alter their provisioning rate based on heterospecific derived anti-predator information; while d) avian heterospecifics are more prevalent in the presence of pied babblers, and can be attracted to areas by playback of pied babbler calls. These results show that species monitor both conspecifics and heterospecifics, and alter their behaviour based on the information they collect.

Mutualisms are delicately balanced partnerships and are increasingly recognized as being fundamental to patterns and processes within ecological systems. Changes to the ecological setting in which such interactions operate can disrupt this balance. By understanding the context-dependent nature of such associations, researchers can begin to understand how changes in the environment can have cascading effects on the entire community within which they occur. Oxpeckers (Buphagus spp.) feed on the ectoparasites of ungulates in sub-Saharan Africa and from the blood of ungulate wounds. Because of this dichotomy in feeding behavior, the role of oxpeckers as consistently beneficial partners of their hosts has been questioned, and it has been suggested that the concept of conditional mutualism be applied to this interaction. I combined observational studies of oxpeckers in Kruger National Park, South Africa, with experiments on oxpeckers in captivity at the Mokopane Biodiversity Conservation Centre, South Africa, to test the hypothesis that the ectoparasite cleaning service provided by oxpeckers to their hosts is context-dependent. The results of my dissertation research demonstrate that the oxpecker-ungulate association has conditional outcomes. Under certain conditions, the oxpecker-ungulate relationship is a nutritional mutualism where ungulates provide food (ticks) for oxpeckers in exchange for a cleaning service. Under other conditions, oxpeckers exploit their hosts to feed from their blood. My findings suggest that a high abundance of the tick species and tick stages oxpeckers prefer is necessary to maintaining an alignment of interests between oxpeckers and ungulates. When ungulates host few ticks of the species oxpeckers prefer, these birds will wound-feed to meet their nutritional demands. Such wound-feeding threatens the balance of the oxpecker-ungulate mutualism. Although oxpeckers frequently wound-fed in captivity, the frequency of wound-feeding events on wild host species was only 3.1% of feeding events. Whether the relationship between oxpeckers and domesticated hosts differs from that between oxpeckers and wild hosts, or if this observed difference is actually a result of researcher constraints in the wild, needs further exploration.

Expansion of common bean (<i>Phaseolus vulgaris</i> L.) crops in the northern Great Planes has been hampered due to the lack of cultivars demonstrating sufficient vitality under low temperature conditions. <i>Phaseolus angustissimus</i> L., a wild bean species, has been previously shown to possess the ability to survive low temperatures in field trials. Freezing tolerance experiments under controlled conditions resulted in P. angustissimus demonstrating a greater capacity for freezing tolerance than <i>P. vulgaris</i>, as all P. vulgaris plants studied were dead at -2.5oC while most P. angustissimus plants treated to the same conditions survived. Exposure to chilling temperatures over five days resulted in stunted growth in both species, but the cultivated bean suffered more compared to the wild bean, as noted by a marked loss in tissue water content over the first three days of chilling. Interspecific macroarray hybridizations of a cDNA library from cold acclimated Medicago sativa L. using cDNAs derived from non-chilled and three-day chilled <i>P. vulgaris</i> and <i>P. angustissimus</i> plants showed that <i>P. vulgaris</i> showed more changes in gene expression after three days of chilling. Also, <i>P. vulgaris</i> showed a general trend towards down-regulation of the transcripts sampled on the third day of chilling compared to <i>P. angustissimus</i>. RT-PCR experiments were conducted using cDNAs from plant tissues exposed to various durations of chilling to confirm the results from the macroarray experiment. These time-course RT-PCR experiments revealed expression patterns across various chilling durations in genes identified from the macroarray. Data from these experiments suggest that <i>P. vulgaris</i> and <i>P. angustissimus </i> seedlings respond differently to low temperature exposure, and that some of the changes in <i>P. angustissimus</i> transcripts monitored here may be useful for researchers in better understanding how Phaseolus species can respond better to chilling temperatures.

No description available.

Expansion of common bean (<i>Phaseolus vulgaris</i> L.) crops in the northern Great Planes has been hampered due to the lack of cultivars demonstrating sufficient vitality under low temperature conditions. <i>Phaseolus angustissimus</i> L., a wild bean species, has been previously shown to possess the ability to survive low temperatures in field trials. Freezing tolerance experiments under controlled conditions resulted in P. angustissimus demonstrating a greater capacity for freezing tolerance than <i>P. vulgaris</i>, as all P. vulgaris plants studied were dead at -2.5oC while most P. angustissimus plants treated to the same conditions survived. Exposure to chilling temperatures over five days resulted in stunted growth in both species, but the cultivated bean suffered more compared to the wild bean, as noted by a marked loss in tissue water content over the first three days of chilling. Interspecific macroarray hybridizations of a cDNA library from cold acclimated Medicago sativa L. using cDNAs derived from non-chilled and three-day chilled <i>P. vulgaris</i> and <i>P. angustissimus</i> plants showed that <i>P. vulgaris</i> showed more changes in gene expression after three days of chilling. Also, <i>P. vulgaris</i> showed a general trend towards down-regulation of the transcripts sampled on the third day of chilling compared to <i>P. angustissimus</i>. RT-PCR experiments were conducted using cDNAs from plant tissues exposed to various durations of chilling to confirm the results from the macroarray experiment. These time-course RT-PCR experiments revealed expression patterns across various chilling durations in genes identified from the macroarray. Data from these experiments suggest that <i>P. vulgaris</i> and <i>P. angustissimus </i> seedlings respond differently to low temperature exposure, and that some of the changes in <i>P. angustissimus</i> transcripts monitored here may be useful for researchers in better understanding how Phaseolus species can respond better to chilling temperatures.