オオムギ雲形病抵抗性品種Brierの遺伝解析と育種への利用  [in Japanese] Genetic analysis of resistance to barley scald (Rhynchosporium secalis) in a field of the resistant cultivar Brier and its application to breeding  [in Japanese]

オオムギ雲形病(病原;Rhynchosporium secalis (Oud.) Davis)抵抗性オオムギ品種Brierと罹病性品種2品種との交配組合せに由来する後代の発病程度を調査し,遺伝解析を行うとともに,発病程度と生育特性,収量関連形質,精麦品質との関係について解析を行い,Brierを母本とした抵抗性品種の育成方法について検討した.北陸地域に優占する雲形病菌レースJ-4a(菌株NB1-1-1)を接種した罹病葉を伝染源として積雪前の分げつ初期に圃場に投入し,出穂30日後に発病程度を調査した.F_2集団の発病程度をもとに分離比の検定を行った結果,圃場におけるBrierの抵抗性は劣性3遺伝子によるものと考えた.抵抗性の遺伝率は比較的高く,初期世代から抵抗性個体の選抜が可能であるが,発病が抑制される条件下では選抜効果が小さいと推察され,圃場においては複数年の検定が必要であると考えた.また,抵抗性品種Brierとの交配によって得られる抵抗性の後代が少なく,優良形質を兼ね備えた抵抗性系統の出現率は低いと考えられるため,抵抗性品種育成のためには抵抗性を有し優良な形質を兼ね備えた系統間でさらに交配を行う必要がある.Brierとの交配によって成熟期が遅れたり,ハンター白度が低くなる傾向が認められることから,Brierを利用するに当たっては,早生で高白度の品種を交配親として用いる必要性が示唆された.

The genetic analysis of scald (Rhynchosporium secalis (Oud.) Davis) resistance of barley plants was conducted among progeny lines derived from crosses that include Brier as a donor parent for resistance. Phenotypic and genotypic correlations between the severity of infection and growth characteristics, yield, and pearled-grain quality were calculated for F_2 generations to clarify problems regarding introducing resistance genes of Brier into Japanese varieties. Barley plants in the early tilling stage in a field were infected with scald by distributing infected barley seedlings which had been inoculated in a greenhouse by fungus strain NB 1-1-1, classified as a dominant race in the Hokuriku district. Genetic segregations of resistance were investigated using progeny lines evaluated on a scale of zero to five for the severity of infection at 30 days after heading in a field. The resistance to scald seemed to be controlled by three recessive genes which were highly heritable, suggesting that it is relatively straightforward to select plants with high-level resistance in an early hybrid generation. However, heritability for resistance was low in environments unsuitable for scald infection and development. Inoculation tests must be conducted for several years to evaluate the resistance of plants. In the present experiments, a small number of progeny with resistance and marked quality was obtained by a single cross with Brier. Therefore, successive crosses among favorable progeny lines appear promising. It is necessary to choose parents to cross with Brier carefully, because Brier's resistance to scald may be associated with undesirable traits such as late maturity and low pearled-grain whiteness.