The Effect of Temperature on Seed Set in Barley Crosses¹

Barley improvement

“…A great many plants must be raised, to have a chance of obtaining a high proportion of the possible recombinations at least initially. By including male-sterile plants in the cross outcrossing, which may be enhanced by management, will continue as the cross is propagated 'in bulk' so giving further chances for genetic recombinations [6,61,166]. Composite crosses have been developed with two aims (I) to investigate the possibility of producing cheaply new, locally adapted varieties from as wide a variety of genotypes as possible and (2) to create readily maintained 'gene banks' in lines progressively better adapted to local conditions.…”

“…In the original CC I, eleven varieties were crossed 32 ways and grown as a mixture, while CC II involved crossing 28 varieties from many areas of the world, in all possible ways [61,154].…”

“…The changes that occur in bulk-propagated populations from composite crosses have excited much interest because, whether or not the crosses readily give rise to new agricultural varieties, understanding the changes that occur should help many breeding programmes [7,11,61,79,82,155,166]. Only in California have composite crosses been grown for an adequate (20 or more) number of generations for some studies.…”

“…A sophisticated approach involves the use of diallele crosses [15]. For example 28 varieties were crossed in all possible ways and progenies were evaluated in comparison with the parents and lines drawn from mixed bulks in the generations F 2 -F 7 [61). Some cultivars were markedly better parents in crosses than others.…”

Factors Influencing Seed Set of Oat Crosses1

“…Coffman and Stevens ( 4) obtained highest seed set at temperatures of less than 85 o F. On very warm days, they secured better results by crossing in late afternoon or evening when the temperature had fallen. Harlan and co-workers ( 6) found that high temperatures prior to emasculation caused barley pollen to ripen while the spike was still tender and easily injured.…”