Leaf morphology is an important component of plant type, which can not only affect light penetration, light absorption, CO2 fixation and photosynthetic efficiency, but also change the canopy structure of the population, optimize light distribution, improve light energy utilization efficiency and promote air permeability. Therefore, reasonable leaf morphology has important production and theoretical significance for improving crop yield.
Recently, the soybean research center of the Institute of Cereals and Oil Crops published a research paper entitled "QTL and candidate genes for heterophylly in soybean based on two populations of recombinant inbred lines" online in the Frontiers in Plant Science. This study combined analysis of QTL mapping based on high-density genetic linkage map, data mining of deep resequencing of parents and differential expression at gene transcription level of multiple populations to research the genetic characteristics of soybean heterophylly, mine relevant QTL, predict candidate genes and explore relevant mechanisms.
This study was based on the high-yield and widely suitable soybean variety Jidou 17, which was released by the Institute of Cereal and Oil Crops, with typical heterophylly characteristics of "narrow top and round bottom" (i.e., the lower leaves are typical oval leaves, the leaf width gradually narrows from bottom to top, and the upper leaves are typical lanceolate leaves), and which was crossed with the round leaf variety Jidou 12 and the lanceolate variety Suinong 14 to construct a high-generation recombinant inbred line (RIL). Two high-density genetic linkage maps were constructed by simplified genome sequencing with f2:6 generation RILs of two populations as materials. For the first time, the ratio (RLS) of the upper leaf shape (LSUP) to the basal leaf shape (LSDOWN) was used to quantify the heterophylly phenotype of plants. Combined with the phenotypic identification in the field for two consecutive years, 8 QTLs related to heterophylly were discovered, of which 4 QTLs located on chromosomes 1, 18, 19 and 20 were major QTLs that had been stable for many years.
By deep resequencing, genomic data of 3 parents with an average depth of 17× was obtained. Four heterophyte-related candidate genes Glyma.01G151800, Glyma.18G279500, Glyma.19G194300 and Glyma.20G116200 were identified in combination with gene function annotation and tissue expression. RT-qPCR analysis showed that the difference in the expression level of the top buds of the candidate genes at different developmental stages caused the heterophylly of Jidou 17.
Researcher ZHANG Mengchen, researcher YANG Chunyan of Institute of Cereal and Oil Crops, and Dr. LIU Chunji of Australian CSIRO are the corresponding authors. Researcher CHEN Qiang and researcher LIU Bingqiang are the co-first authors. This research was supported by the National Modern Agricultural Industry Technology System (CARS-04-PS06), the National Natural Science Foundation of China (31471522), the Hebei Soybean Modern Seed Industry Science and Technology Innovation Team (21326313D-4), and the Natural Science Foundation of Hebei Province (C2020301020).
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