Abstract
Annual-form-wild (AFW) rice developmentally changes the vegetative plant architecture from flat to elect shape. The main objective of the present study is to suggest that the change might be related to competitive ability (CA). Recombinant inbred lines (RILs) derived from a cross between an AFW rice and a cultivar were grown under high-density (H) and low-density (L) conditions in a weedy paddy field. At two and three months after transplanting (MATs), we evaluated the two traits associated with utilization of light resource, tiller angle (TA) and actual plant height (APH), and amount of the growing weeds using an index, weed-denseness score (WDS). Then, DC-TA, DC-APH and SC-WDS was defined as the amount of change in TA, APH, and WDS from two to three MATs, respectively. Multiple regression analysis revealed that only DC-TA significantly affected SC-WDS specific under H condition that is relatively similar to habitats of AFW rice. Quantitative trait locus (QTL) analyses identified that one of the two QTLs associated with DC-TA shared a linked molecular marker with a QTL associated with SC-WDS only under H condition. Further, RILs with AFW-rice-derived allele on the QTL associated with DC-TA tended to show drastic changes of TA toward narrow angle as well as large decreases of weed amount. All the QTLs associated with DC-APH were not linked to the QTL associated with SC-WDS under H condition. Therefore, it is suggested that under the crowded conditions during the late plant development, AFW-rice plants might not survive through canopy domination but elevate CA through increases of efficiency of capturing light due to changes from wide to narrow tiller angle. Since flat-plant shape of AFW rice during the early development would have been evolved by trampling pressures, the present finding suggest that different selective pressures in life time might have cooperatively evolved the developmental change.
Highlights
The wild progenitor of Asian cultivated rice, Oryza rufipogon Griff., tends to show annual-perennial continuum within a species [1,2]
Multiple regression analysis revealed that only Developmental change of (DC-)tiller angle (TA) significantly affected SC-weed-denseness score (WDS) specific under H condition that is relatively similar to habitats of AFW rice
While the Developmental Change of Vegetative Plant Architecture of Annual-Form-Wild Rice (Oryza rufipogon Griff.) Elevates 679 Competitive Ability during the Late Development under a Dense Condition points, which were positioned under the line of Y = X – 1, indicate that the genotypes might significantly decrease fresh weight of weeds (FWW) during the period
Summary
The wild progenitor of Asian cultivated rice, Oryza rufipogon Griff., tends to show annual-perennial continuum within a species [1,2]. The habitat is mainly characterized by the three disturbances, drought stress in dry season, trampling pressures by large size of mammals during the early vegetative plant development and water stress in rainy season [3,4,5]. Many ecological experiments as to fate of AFW-rice populations introduced into weedy natural habitats have revealed that AFW-rice populations disappeared in an early generation [4,6,8,9,10]. It is because most of buried seeds could not germinate when weeds grew. It was expected that AFW rice would show a high competitive ability (CA) during the vegetative plant development if the seedlings
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