Weith Sean K, Jahufer M Z Zulfi, Hofmann Rainer W, Anderson Craig B, Luo Dongwen, Ehoche O Grace, Cousins Greig, Jones E Eirian, Ballard Ross A, Griffiths Andrew G
AgResearch, Grasslands Research Centre, Palmerston North, New Zealand.
Faculty of Agriculture and Life Sciences, Lincoln University, Lincoln, New Zealand.
Front Plant Sci. 2022 Sep 20;13:953400. doi: 10.3389/fpls.2022.953400. eCollection 2022.
White clover () is integral to mixed pastures in New Zealand and temperate agriculture globally. It provides quality feed and a sustainable source of plant-available nitrogen (N) N-fixation through symbiosis with soil-dwelling bacteria. Improvement of N-fixation in white clover is a route to enhancing sustainability of temperate pasture production. Focussing on seedling growth critical for crop establishment and performance, a population of 120 half-sibling white clover families was assessed with either N-supplementation or N-fixation inoculation with a commercial strain (TA1). Quantitative genetic analysis identified significant ( < 0.05) family additive genetic variance for Shoot and Root Dry Matter (DM) and Symbiotic Potential (SP), and Root to Shoot ratio. Estimated narrow-sense heritabilities for above-ground symbiotic traits were moderate (0.24-0.33), and the strong ( ≥ 0.97) genetic correlation between Shoot and Root DM indicated strong pleiotropy or close linkage. The moderate ( = 0.47) phenotypic correlation between Shoot DM under symbiosis vs. under N-supplementation suggested plant growth with mineral-N was not a strong predictor of symbiotic performance. At 5% among-family selection pressure, predicted genetic gains per selection cycle of 19 and 17% for symbiotic traits Shoot DM and Shoot SP, respectively, highlighted opportunities for improved early seedling establishment and growth under symbiosis. Single and multi-trait selection methods, including a Smith-Hazel index focussing on an ideotype of high Shoot DM and Shoot SP, showed commonality of top-ranked families among traits. This study provides a platform for proof-of-concept crosses to breed for enhanced seedling growth under symbiosis and is informative for other legume crops.
白三叶草（）是新西兰混合牧场以及全球温带农业不可或缺的一部分。它能提供优质饲料，并通过与土壤中栖息的细菌共生实现植物有效氮（N）的可持续固定。提高白三叶草的固氮能力是增强温带牧场生产可持续性的一条途径。着眼于对作物建立和表现至关重要的幼苗生长，对120个半同胞白三叶草家系群体进行了评估，分别采用了施氮或接种商业菌株（TA1）进行固氮处理。数量遗传学分析确定了地上部和根部干物质（DM）、共生潜力（SP）以及根冠比的显著（<0.05）家系加性遗传方差。地上部共生性状的估计狭义遗传力适中（0.24 - 0.33），地上部和根部干物质之间的强（≥0.97）遗传相关性表明存在强多效性或紧密连锁。共生条件下地上部干物质与施氮条件下地上部干物质之间的中等（=0.47）表型相关性表明，利用矿质氮的植物生长并非共生表现的有力预测指标。在5%的家系间选择压力下，共生性状地上部干物质和地上部共生潜力每选择周期的预测遗传增益分别为19%和17%，突出了在共生条件下改善早期幼苗建立和生长的机会。单性状和多性状选择方法，包括侧重于高地上部干物质和地上部共生潜力理想型的史密斯 - 黑兹尔指数，显示出各性状中排名靠前的家系具有共性。本研究为进行概念验证杂交以培育共生条件下幼苗生长增强的品种提供了一个平台，对其他豆科作物也具有参考价值。
