Novel strategies for genetic improvement of disease resistance in perennial ryegrass

多年生黑麦草(PRG)是英国牲畜的主要饲料。安德森网斑是PRG的一种严重的真菌疾病，英国处于高风险或中等风险。在第一次收获中，产量效应可以超过每公顷1T DM(英国植物育种者协会推荐名单)。现有的二倍体品种中，抗性较好的品种较少，英国培育的高糖草品种抗性较差。使用杀菌剂不是一个可行的选择。减少使用HSG品种会导致销量下降，而进口品种的销量会增加，这些品种抗性较高，但没有高糖含量，从而提高了反刍动物的营养效率。该项目将英国唯一拥有的饲草和豆类种子生产和批发公司(Geral Holdings Ltd)与英国主要的饲用植物育种和遗传学研究组织(IBERS、Aberystwyth University)组成一个联合体，拥有技术和商业经验，以提供具有HSG特征的新的抗网斑病PRG品种。Ibers，Aberystwyth大学将利用一种新的回交策略，辅以基因组选择，培育抗网斑病的HSG品种。这将提高抗病杂交种恢复先前农艺性状和HSG性状的速度。在黑麦草育种计划中，这是以前没有做过的。新的抗网斑病黑麦草品种将有助于GHL保持和增加在英国和海外的市场份额。我们已经鉴定出具有高抗网斑病能力的生态型。它们将首先与AberWolf杂交，AberWolf是一个高性能、低网斑病抗性的HSG品种。将对F1后代进行抗病表型评估，并使用4000分子标记SNP芯片进行基因分型。这使我们能够确定净斑病抗性的数量性状基因座(QTL)。其次，开发了预测模型，以求出农艺性状和牧草品质性状的基因组估计育种值。这将使我们能够选择抗病和HSG性状的最佳候选者。将对F1植株进行多交，以确保抗病性状的分离。到第五年，将完成与经常性的HSG亲本的另外三轮回交。种子将从第三年起留作在德文郡的小规模田间试验，用于剩下的两年。这些田间试验还将包括一系列具有高或低水溶性碳水化合物(WSC)含量的敏感和抗性材料，以供比较和作为对照。这些严格的试验将确保到项目结束时，除了AberHSG品种在产量、WSC和消化率方面的有益特性外，我们还将拥有具有更高净斑点抗性的种群。将开展一系列活动来宣传这项工作，从而促进这些新品种在农场上的快速推广。这包括与种子分销商、顾问和农民的沟通。这项技术将在各种畜牧展上展示，如果可能的话，包括示范田。GHL还将为农民生产出易于遵循的管理指南。

Perennial ryegrass (PRG) provides the majority of forage for livestock in the UK. Drechslera andersonii or net blotch is a serious fungal disease of PRG, and the UK is at high or medium risk. Yield effects can be over 1t DM per hectare in the first cut (British Society of Plant Breeders - Recommended List). Few current diploid varieties have good resistance, and the UK bred high sugar grass (HSG) varieties show poor resistance. Fungicide use is not a viable option. Reduction in the use of HSG varieties will lead to decreasing sales and increase in imported varieties with higher resistance, but without the high sugar content, which improves ruminant nutrition efficiency. The project brings together the only UK owned forage grass and legume seed production and wholesale company (Germinal Holdings Ltd), and the major forage plant breeding and genetics research organisation within the UK (IBERS, Aberystwyth University) in a consortium that has the skills and commercial experience to deliver new net blotch resistant PRG varieties with HSG characteristics. IBERS, Aberystwyth University will breed net blotch resistant HSG varieties using a novel backcross strategy aided by genomic selection. This will increase the speed with which disease resistant hybrids recover previous values of agronomic and HSG traits. This has not been done before in a ryegrass breeding programme. New net blotch resistant HSG ryegrass varieties will help GHL maintain and increase market share in the UK and abroad. We have identified ecotypes with high net blotch resistance. They will initially be crossed with AberWolf, a high performing HSG varieties with low net blotch resistance. The F1 progeny will be assessed phenotypically for disease resistance, and genotyped with a 4000 molecular marker SNP chip. This allows us to identify quantitative trait loci (QTLs) for net blotch resistance. Secondly, prediction models have been developed to derive genomic estimated breeding values for agronomic and forage quality traits. This will enable us to select the best candidates for disease resistance as well as HSG traits. A polycross of the F1 plants will be performed to guarantee segregation of the disease resistance traits. By year 5 three further rounds of backcrossing with the recurrent HSG parent will have been completed. Seed will be set aside from year 3 for small scale field trials in Devon for the remaining two years. These field trials will also include a wide range of susceptible and resistant material with high or low water soluble carbohydrate (WSC) content for comparison and as controls. These rigorous trials will ensure that by the end of the project, we will have populations with much higher net blotch resistance in addition to the beneficial properties of AberHSG varieties in terms of yield, WSC and digestibility. A range of activities will be undertaken to publicise this work, and thus facilitate fast on-farm uptake of these new varieties. This includes communication with seed distributors, advisors and farmers. The technology will be demonstrated at various livestock shows, including demonstration plots, where possible. GHL will also produce easy to follow management guidelines for farmers.