An Approach to the “Grain-Filling Problem” in Rice through the Improvement of Its Sink Strength

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  • Kato Tsuneo
    Faculty of Biology-Oriented Science and Technology, Kindai University

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Other Title
  • イネにおけるシンク強度の改良による「登熟問題」へのアプローチ

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Description

Many rice cultivars with numerous spikelets in a panicle (extra-heavy panicle types, EHPTs) have been developed to attain higher grain yield. However, there is a “grain-filling problem” for these EHPTs: they did not attain expected higher yield in many cases because of their low degree of grain filing, resulting from the increase in inferior spikelets showing poor grain filing. This short review addresses an approach toward the grain-filling problem of EHPT rice, particularly for the genetic improvement of its sink strength, and proposed two strategies for the resolution of this problem. The first strategy is the improvement of the poor grain filling in the increased inferior spikelets. This may be realized by utilizing suggested alleles for good grain filling at APS2, APL2 (they correspond to ADP-glucose pyrophosphorylase subunits), and SUT1 (sucrose transporter) loci. These alleles are expected to accelerate the unloading and metabolism of sucrose in developing endosperm, and to maintain a gradient of sucrose concentration from source to sink. The second strategy is the construction of a novel EHPT, in which its spikelet number is increased by increasing superior spikelets. A selection experiment strongly indicated that this strategy may be attained by the selection to increase the number of primary branches per panicle. Although these two strategies are needed to evaluate further, it is suggested that they are available to future breeding of EHPTs with good grain filling, and they can be combined with other approaches to this grain-filling problem.

Journal

  • Journal of Crop Research

    Journal of Crop Research 65 (0), 1-11, 2020

    The Society of Crop Science and Breeding in Kinki, Japan

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