Barley cultivars Kitchin (C.I. 1296) and Jet (C.I. 967), resistant to scald (incited by Rhynchosporium secalis (Oud.) Davis), and cultivars Tifang (C.I. 14373), C.I. 9819, and C.I. 7584, resistant to net blotch (incited by Pyrenophora teres Drechs.), were crossed to the primary trisomics in the cultivar Betzes. F2 segregation ratios were studied to determine chromosomal location of the resistance genes. Kitchin was found to contain a single scald-resistance gene, Rrs9, on chromosome 4. Jet contained scald-resistance genes rrs1 and rrs6 on chromosomes 3 and 4, respectively. Tifang contained a single gene, Rpt1a, for net-blotch-resistance on chromosome 3. C.I. 7584 contained a single net-blotch-resistance gene, Rpt3d, on chromosome 2. C.I. 9819 contained net-blotch-resistance genes Rpt1b and Rpt2c on chromosome 3 and 5. Some uses of this information are discussed.
Canopy temperature under a set of environmental conditions is an integrated result of the energy absorption and dissipation mechanisms acting within the canopy. The relative magnitude of these various mechanisms may affect the amount and efficiency of water use. We studied the influence of different morphological features such as plant color, awn length, and waxiness on canopy temperatures of field grown barley (Hordeum vulgare L.). Morphological differences were obtained by using barley lines isogenic for the various features. Canopy temperatures were measured with an infrared thermometer on five different dates within a 21‐day period after heading. Light‐colored plants were significantly cooler (5% level) than normal‐colored plants. Awn length significantly (5% level) affected canopy temperatures of a sixrow variety; awned canopies were cooler than awnless. Awn length did not affect the canopy temperatures of a two‐row variety. Waxiness did not affect canopy temperatures. Calculations indicate that differences in canopy temperatures due to plant morphology could significantly affect water use.
The starch granule size and distribution has been determined on 29 different samples of barley. There is a wide range in the ratio of small to large granules which varies from a minimum of 5.5:1 to a maximum of 37:1. Small granules were separated from large granules in four varieties and the average weight of the granules determined. From these values the actual percentage of small granules in the original barley starch was determined. Small granule starch may account for from 6.2–30.6% of total starch weight in the varieties examined.
Six spontaneous shrunken endosperm mutants in barley (Hordeum vulgare L.) were identified and described. Five of the mutants (se1 through se5) were inherited as maternal plant monofactorial recessives and one mutant se6 was inherited as a monofactorial recessive expressing xenia. The mutants varied in fertility, seed weight, and seive size assortment. Four mutants were located on chromosome one, one on chromosome three, and one on chromosome six, by using translocation breakpoints as markers. Mutants similar to se1 through se5 could be used as males in commerical hybrid seed production. Mutants similar to se6 could be used as preflowering selective genes for the female stock for hybrid seed production.
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