小麥根系性狀關聯性定位與環境基因型交感分析

Abstract

小麥是世界上重要的糧食作物之一，主要種植在溫帶環境，最適生長溫度約為15至25℃。受到極端氣候的影響，小麥生長可能面臨高溫逆境的傷害。目前小麥耐熱的研究以地上部性狀為主，根系對於高溫的反應及植株耐熱的貢獻程度仍不是很清楚。本研究首先調查小麥自然種源的根系性狀變異程度，透過238個小麥品系的苗期最大根長與57,398個SNPs的全基因體關聯性分析結果，我們在染色體6A、6B及6D各偵測到一個顯著區間。藉由探勘同源基因與小麥根系組織表現量的資訊，這3個區間內共發現10個基因在其他物種具有調控根系發育的功能。接著，我們挑選53個根長差異懸殊的小麥品系，在16度生長箱環境下，每3天調查品系的根長與總根長性狀，並繪製生長速率曲線。利用人為判斷與K-means方式對53個品系的生長速率分群，結果顯示K-means方式較人為判斷準確且有效率。小麥幼苗期的總根長是由5個根系結構所組成，這53個品系的根系結構具明顯不同的生長速度，此特性是否會影響小麥水分、養分的吸收及利用，將需要更多的實驗證明。最後，為了分析根系結構對溫度變化的反應，我們挑選20個根長差異極大的品系，以Turface作為栽培介質，在2022年的4月、6月及7月 (月均溫分別為25.7℃、33.1 ℃與36.6℃) 的溫室環境下種植。利用GGE biplot及AMMI兩種方法分析20個品系的根系性狀與溫度的交感程度，結果顯示7個品系的根系具有較佳的穩定性與較高的性狀值。總結本論文的研究成果，除了提供種源及遺傳資訊可應用在分子輔助選種，生長箱與溫室試驗則呈現不同遺傳背景的小麥品系，在控溫及多個溫度下的根系結構變化過程。期望未來能結合田間試驗，評估在高溫逆境下根系結構變化與產量的關係。

Wheat is primarily grown in temperate environments, with an optimal temperature range between 15 and 25°C. However, extreme weather conditions, particularly high-temperature stress, can negatively impact wheat cultivation. While current research on wheat heat tolerance mainly focuses on above-ground traits, the contribution of root traits to plants heat tolerance is unclear and should not be overlooked. This study utilized 238 wheat accessions and 57,398 SNPs for a genome-wide association analysis of maximum root length (MRL). Significant regions were identified on chromosomes 6A, 6B, and 6D. Candidate genes within these regions were further investigated for their orthologous gene function and expression profiles in root tissue. Ten candidate genes were identified across the three regions, showing relevance to root tissue expression, and their orthologous genes were related to root development and growth. 53 wheat accessions showing extreme long and short root length were selected for further investigation. Plants were grown at 16°C, MRL and total root lengths was phenotyped every three days. The growth rate was calculated and plotted for each trait, and classification of the 53 accessions based on a similar growth pattern was performed using both manual judgment and K-means clustering method, the results showed K-means method generated superior classification. Wheat root system architecture (RSA) could be categorized into five components, significant growth differences in each composition was observed among the 53 accessions, providing valuable information to study the variation of RSA and water and nutrient uptake efficiency in the future. To analyze how wheat RSA variation responds to various temperatures, 20 accessions with substantial differences in root length were grown in a greenhouse in April, June, and July of 2022, the average daily temperatures were 25.7℃, 33.1℃, and 36.6℃, respectively. Most accessions exhibited the highest trait values in June, with the lowest in April. GGE biplot and AMMI analysis results showed seven varieties had better stability and higher trait values across three growing conditions. In summary, this study identified wheat germplasm and candidate genes associated with regulating maximum root length, these genetic information can be utilized in marker-assisted breeding. The growth chamber and greenhouse experiments detailed the root growth variation among diverse cultivars and their responses to different temperatures. We look forward to conduct experiments in the field to reveal the relationship between RSA variation and wheat yield.