The effects of crop plant height, relative time of weed emergence (RTE) and crop seed vigour and dormancy on the ability of Rht (Reduced height) lines of winter wheat to maintain yield and suppress weeds, were investigated. Near Isogenic Lines (NILs) of Rht lines in Mercia cultivar background were planted with oat as a model weed. As NILs were genetically similar apart from the Rht genes, actions and interaction of RTE and crop height were assessed without confounding effects of other traits associated with competitive ability. Seed vigour and dormancy were included in case they influenced RTE. In competition with oat, the crop yield increased and yield losses decreased as the oat emergence was delayed. The yield loss was greater in the dwarf NILs (Rht-Bl c: 49% and Rht12: 64%) compared to the Mercia control (18%) and semi-dwarfNILs (25%). RTE had no effect on crop height or biomass or light interception in both the years. Yield increased linearly with the crop height both in the presence and absence of weeds. Weed-free yields were always exceeding the weedy yields irrespective ofRTE. Whether the Rht lines were sensitive or insensitive to gibberellins, did not make any difference to yield maintenance and weed suppression, but their weed suppressive ability was generally poor. High vigour cv. Mercia and Rht-Bl c seed lots competed better against weeds than low vigour ones, but the effect related to a ,higher crop plant population as the effect of R TE of weeds was the same for low and high vigour lots. The acquisition of germinability and dormancy during maturation of grams and subsequent field emergence was studied in 19 winter wheat NILs in cv. Mercia, Maris Huntsman and Maris Widgeon backgrounds. High levels of dormancy were found in the dwarf allele Rht-Bl c in all three backgrounds and also in Rht-Dl b + Rht-Bl c in Maris Huntsman and Maris Widgeon backgrounds. Longer mean time of emergence, lower percentage of emergence, shorter coleoptile length, higher Hagberg Falling Number and GA insensitivity were the causes for the delay in emergence which slightly reduced the ability of Rht-Blc and Rht-Dlb+Rht-Blc to compete against weeds. Upright with erect leaf NIL's early season height, maximum height were positively correlated with grain yield and weed suppression, and negatively correlated with crop yield loss and weed seed production. Overall, crop height was found to be more important in achieving weed suppression than relative time of weed emergence.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:553173 |
| Date | January 2011 |
| Creators | Harris, Kumuthini D. |
| Publisher | University of Reading |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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