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The effects of 12°, 13°, 24° and 30°C temperatures; 24, 20, 16 and 12 hour photoperiods; 2000 and 500 ft.-c. light intensities and light high and low in far-red energy on numbers of florets and percent sterility per head and per plant were studied on combinations of seventeen barley varieties. Numbers of florets per head and per plant were reduced with an increase in temperature. Numbers of florets were increased with a decrease in photoperiod at low, but not at high, temperature. At the low light intensity there was a slight decrease in number of florets per head and a pronounced reduction in tillering. The virtual absence of far-red energy had no effect on tillering, but caused a significant increase in number of florets per tiller head. Plant sterility was lowest at 18°C. Main head sterility was low at 12° and 18°C but was markedly increased at 24° and 30°C. Tiller head sterility was much higher than that of main heads at all temperatures and was as high at 12°C as at 24°C. Photoperiod had little effect on main head sterility except for causing a marked increase at 12 hour. At the optimum temperature for development (13°C), intermediate photoperiods had the lowest plant sterility. The reduction in light intensity caused a 30 percent increase in plant percent sterility. Light low in far-red energy caused an average increase of 25 percent in plant sterility. Varieties had significant interactions with temperature, photoperiod, light intensity, and light quality in determining the numbers of florets differentiated per head and per plant. Temperature and light intensity were the only factors to interact with variety for percent sterility. The varieties Aria, Asa, Betzes, O.A.C. 21, Palliser, Pirkka, Titan, Trebi, and Vantage were especially sensitive to the stress conditions imposed. / Land and Food Systems, Faculty of / Graduate

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The cytological and breeding behavior of barley with 8 pairs of chromosomes, of which 2 pairs are interdependent were evaluated. The 8II material originated from selfed progeny of a Balanced Tertiary Trisomic 57a msg16. Chromosome interdependence was established after a naturally occurring reciprocal translocation between the normal chromosome 5 and the extra interchanged 57a chromosome. The interdependent chromosomes are fragment chromosomes. A Male Sterile Facilitated Recurrent Selection Population (MSFRSP) of 8II plants was developed. Eight chromosome paired plants were crossed onto male sterile plants from barley Composite Cross XXXII. The F₁ plants from the 7II x 8II crosses carried a characteristic 15-chromosome cytotype. In the F₂ of this cross, 5 different cytotype classes of progeny were isolated by root-tip chromosome and microsporocyte analyses: 7II, F₁, 8II, tertiary trisomic where the extra chromosome is a fragment chromosome and a Unique-16 chromosome cytotype which consisted of 6 normal pairs, one pair of fragments, one normal chromosome 5 and one fragment chromosome from the other pair of fragments. The F₂ population was approximately 30% 7II, 50% F₁ and 20% 8II cytotype progeny. Microsporocytes observed from F₂ cytotype plants indicated that the 7II and 8II progeny went through normal meiosis. The F₁ cytotypes produced functional gametes with 7 normal chromosomes, 8 chromosomes equivalent to gametes produced by 8II plants and gametes with 7 normal chromosomes plus a fragment chromosome. The tertiary trisomic progeny produced functional gametes with 7 normal chromosomes and gametes with 7 normal chromosomes plus a fragment chromosome. The Unique-16 cytotype produced functional gametes with 7 normal chromosomes, 8 chromosomes equivalent to gametes produced by 8II plants, 7 chromosomes plus a fragment chromosome and 9-chromosome gametes with 6 normal chromosomes plus 3 fragment chromosomes, two of which are a pair. Crosses and their reciprocals between 7II plants and plants of each F₂ cytotype indicated that the cytological stabilty of an 8II or 7II population would be disrupted if contaminated by pollen from 7II or 8II plants respectively. Growing the populations in physical isolation from each other is a must in order to maintain the cytotype of the population homozygous

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"November, 2003" / Bibliography: leaves 174-191. / viii, 196 leaves : ill. (some col.), photos (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This study aims to identify and characterise novel alleles for key malting quality genes from wild barley, wild barley being a source of novel genetic variation that could be exploited to develop superior barley varieties. / Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, Discipline of Plant and Pest Science, 2004