Potential of transmission of Pyricularia graminis-tritici from plant to seed and from seed to seedling in wheat genotypes with different degrees of blast resistance

Abstract: Transmission studies of Pyricularia graminis-tritici by wheat seed can help establishing pathogen tolerance standards in crops. Four genotypes, each one with different responses to blast, were inoculated with five volumes of fungal suspension (1,5x105 spores.mL-1), in order to obtain 0, 5, 10, 20 and 30% of plants inoculated in the experimental unit. The potential of transmission of P. graminis-tritici from plant to seed was evaluated by the incidence of the fungus in the seeds produced. Under controlled conditions, the transmission rate of the fungus from seed to seedling was evaluated. Blast incidence in field allowed a high incidence of P. graminis-tritici in the seeds, especially in the genotypes considered susceptible. The transmission of fungus from the seeds to seedlings occurred 7, 14 and 21 days after sowing, at low rates. There was a relationship between the presence of blast in field and the incidence of P. graminis-tritici in seeds produced by the genotypes BRS 264, VI 98053, CD 116 and CD 104. Inoculation of 5, 10, 20 and 30% of plants with fungus can generate a high incidence of the pathogen in field and in the seeds produced, but it doesn`t guarantee a high transmission rate from seed to seedling, which is low under controlled conditions.

摘要：针对小麦禾谷梨孢菌（Pyricularia graminis-tritici）通过小麦种子的传带研究，可为作物病原菌耐受性标准的制定提供理论支撑。本研究选取4个对稻瘟病抗性表现各异的小麦基因型，采用浓度为1.5×10^5孢子·mL^-1的真菌悬浮液，设置5种接种梯度以实现实验单元内0%、5%、10%、20%、30%的植株接种率。通过检测收获种子中的病原菌带菌率，评估该菌从植株向种子的传带潜力；并在可控环境条件下，测定其从种子向幼苗的传带效率。研究结果表明，田间稻瘟病发病程度较高时，收获种子中的小麦禾谷梨孢菌带菌率也随之升高，这一现象在感病基因型中尤为显著。播种后7、14、21天均可检测到病原菌从种子向幼苗的传带，但传带率均处于较低水平。基因型BRS 264、VI 98053、CD 116及CD 104的田间稻瘟病发病情况，与其收获种子中的小麦禾谷梨孢菌带菌率存在显著相关性。以5%、10%、20%、30%的植株接种率进行病原菌接种，可使田间及收获种子中的病原菌带菌率处于较高水平，但无法确保较高的种子-幼苗传带率——该传带率在可控环境条件下始终处于较低水平。