Hybrids between wheat and jointed goatgrass have long been presumed to be sterile; however, seed were found on hybrid plants in 1990. Field studies were conducted in 1995 and repeated in 1996. One to ten hybrid plants were planted in variable populations of wheat and jointed goatgrass to determine the rate of seed set and viability of seed produced on hybrids. An average of 2.3% of florets set seed in 1995 and 3.8% of florets set seed in 1996. Seed were set in all treatments. Hybrid population had no effect on seed set. The BC1 (first backcross) seed produced in the field studies were separated according to seed condition, full or shrivelled, and were tested for germination. Ninety-four percent of the full seed germinated in each year and 79% and 84% of the shrivelled seed germinated in 1995 and 1996, respectively. Field studies were conducted in 1996 and 1997 using seed set on hybrids grown in populations of 150 jointed goatgrass or 150 wheat plants in the previous year's field study. Ten BC1 plants were planted into plots containing 100 jointed goatgrass plants. From 0.25 to 20.29% of florets per plot set seed. Greenhouse studies were conducted in 1997 and repeated in 1998 using BC1 seed produced in the previous year's field study. Seed resulting from self-pollination occurred on 4.1% or 59 plants in 1997 and 2.1% or 16 plants in 1998. Percent seed set ranged from 0 to 80.22% on a per plant basis. Parental population and seed set on BC1 plants can not be predicted based on coleoptile color, germination day, leaf width, number of veins in the leaf, presence or number of hairs on leaf margin, plant posture, number of spikes produced, culm height, spike length, or resemblance to parents. / Graduation date: 1999

Pre-harvest sprouting in wheat costs farmers millions of dollars every year. Pre-harvest sprouting tolerance (PST) has minimized this problem, but improvement of PST is still necessary. Synthetic hexaploid wheats (synthetics) have been used as sources of genes coding for many useful traits. Two studies evaluated the PST of a synthetic (Altar 84/Aegilops tauschii) and investigated its potential as a source of PST in crosses with wheat cultivars. The first study compared the synthetic with selected wheat checks for PST and with its parent Altar 84 for the germination response of these genotypes to controlled wetting treatments applied to field-grown intact spikes and threshed seed. Spikes were rolled in wet germination paper and the percentages of germinated seed were determined after seven days. Threshed seeds in Petri dishes were wetted with water and vegetative floral tissues (chaff) extracts. Germinating seeds were counted daily for 14 days. The synthetic was more tolerant than Altar 84 and was classified as moderately sensitive. The improved PST of the synthetic over Altar 84 was attributed to Aegilops tauschii. Seed dormancy and water-soluble substances in the chaff of the synthetic and other genotypes appeared to contribute to their PST. The second study used random inbred F��� lines obtained from single and backcrosses between the synthetic (red-seeded) and the sensitive wheat cultivars Opata F��� (red-seeded) and Bacanora 88 (white-seeded). Seed coat color and germination responses of the F5 lines subjected to a five-day spike wetting treatment were evaluated. Pre-harvest sprouting tolerance was moderately to highly inheritable and largely controlled by additive gene effects in the studied populations. An association between red seed coat color and PST was observed but white recombinant lines more tolerant than their sensitive parent were obtained. The synthetic can be used to improve wheats with red and white seed coats. The potential use of the synthetic as a PST source was discussed and a breeding strategy suggested. / Graduation date: 1999