Abstract
Spike hetero branching wheat (Triticum aestivum) (SHBW) has one main rachis, but has branched rachises at lower parts of main rachis. This type of spike could increase greatly grain number by bearing grain in branching rachis. In this study, field experiments were conducted at three locations in Huanghuai wheat zone during two growing seasons (2008-2010). The rachises length, node number, grain number, and grain weight were investigated within five different spikes parts. The results showed that the proportion of the length of upper no-branching part to that of lower branching part within the main rachis varied from 0.49-0.99; The coefficient of variations (CVs) of main rachis length, node number within main rachis and grain number and thousand grain weight within the upper part of main rachis were 9.78%, 8.49%, 21.73% and 17.32%, respectively, but CVs of these traits within the branched rachises were 54.45%, 37.21%, 36.80%, and 19.45%, respectively. This indicated that the morphological characters within branched rachises were more easily influenced by external environments. Grain number in the whole spike and average branched rachises length were unstable under various environments and the two traits should be regarded as the main choice factors in future breeding selection in SHBW.
Highlights
In normal common wheat a rachis is the main axis of the inflorescence or spike
The results showed that the proportion of the length of upper no-branching part to that of lower branching part within the main rachis varied from 0.49-0.99; The coefficient of variations (CVs) of main rachis length, node number within main rachis and grain number and thousand grain weight within the upper part of main rachis were 9.78%, 8.49%, 21.73% and 17.32%, respectively, but CVs of these traits within the branched rachises were 54.45%, 37.21%, 36.80%, and 19.45%, respectively
Chromosomal location of the genes for the branched rachises character in the bread wheat line, Yupi Branching was determined by monosomic analysis, and the results indicated that chromosome 2D, 4A, 4B and 5A of bread wheat carry genes for branched rachises character
Summary
In normal common wheat a rachis is the main axis of the inflorescence or spike. SHBW has a main rachis as normal common wheat, but displays two different spike morphotypes in a spike (Figure 1). Spikelets are borne on branching rachis node and might offer more possibility for more florets in a spike. The genetics of this supernumerary spikelet in wheat has been studies for over ninety years. The inheritance of branched rachises in common wheat was found to be controlled by two recessive genes with evidence for the possibility of a repressor(s) in crosses between normal and SHBW lines (Koric, 1980). The gene on chromosome 2D has the strongest effect on the expression of the branched rachises character (Peng et al, 1998)
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