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Title: PLANT HEIGHT COMPONENTS AND GIBBERELLIC ACID RESPONSE OF OAT DWARF LINES

Author
item MILACH, S - UNIVERSITY OF MINNESOTA
item Rines, Howard
item PHILLIPS, R - UNIVERSITY OF MINNESOTA

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2001
Publication Date: 8/15/2002
Citation: MILACH, S.C., RINES, H.W., PHILLIPS, R.L. PLANT HEIGHT COMPONENTS AND GIBBERELLIC ACID RESPONSE OF OAT DWARF LINES. CROP SCIENCE. 2002. V. 42. P. 1147-1154.

Interpretive Summary: In crop production, major losses in grain quality and yield often occur from plants breaking or falling over in wind and rain storms. Such losses are particularly prevalent in high fertility situations favoring tall, lush plant growth. The development of shorter, more compact plant types helps plants resist this breaking or lodging. In fact, the development in wheat and rice of shorter plant types able to remain standing under fertile soil conditions was the key factor in the "Green Revolution" in these crops. Three different "dwarfing" mutants in the cereal oat have been described that give shorter plant height. We analyzed the growth patterns of these mutants and also how they respond to the plant hormone gibberellic acid. The growth pattern effect varied among the three mutants with one reducing length of all plant parts, one reducing only the lower stem, and the third only the upper part of the stem. Unlike the primary dwarfing mutant used in nwheat breeding improvement, all three oat mutants were still responsive to applications of the gibberellic acid plant growth hormone. An understanding of growth pattern differences and hormone responsiveness of these mutants will help geneticists and breeders to design oat varieties with the desired shorter plant type. Such oat varieties should stand better in the field and retain high quality, non-weathered grain that is easier for farmers to mechanically harvest.

Technical Abstract: Lodging can cause severe losses in grain yield and quality in cereal crops. The use of oat (Avena sativa L.) dwarfing genes in breeding programs to improve lodging resistance has been limited, mainly due to decreases in yield and grain quality in many environments. The objectives of this study were to evaluate the effects of the dominant Dw6, Dw7, and Dw8 dwarfing genes on plant height components, and the gibberellic acid (GA) response o the dwarf lines. Plant height components including internode length, panicle length, and panicle exertion were measured in plants of three non- dwarf and nine dwarf lines. Dwarf genotypes were compared to their respective non-dwarf progenitor lines. Results indicate that the three dwarfing loci differentially reduced plant height. The Dw6 gene reduced primarily the length of the three uppermost internodes, but not internode number. The Dw7 gene reduced both internode length and number. The Dw8 gene esignificantly shortened all internodes but did not affect internode number The dwarf lines that carry these dwarfing loci are responsive to exogenously added GA3. They are also responsive to added GA1 and GA20 and thus the mutations appear not to involve disruptions of the conversion of GA20 to GA1. The GA-sensitivity and the dominant or semi-dominant inheritance pattern of the Dw6, Dw7, and Dw8 mutants indicate that they are variants in some type of negative regulation of GA metabolism in hexaploid oat.