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How root traits would be affected by soybean yield improvement? An examination of historical cultivars grafted with record-yield cultivar scion

Li, Shengyou, Wang, Wenbin, Cao, Yongqiang, Wang, Changling, Yan, Chunjuan, Dong, Lijie, Wu, Lishi, Xie, Futi, Song, Shuhong
Plant and soil 2019 v.439 no.1-2 pp. 19-30
biomass, breeding, cultivars, filling period, genetic improvement, grafting (plants), grain yield, photosynthesis, pot culture, root shoot ratio, roots, scions, shoots, soybeans, starch
BACKGROUND AND AIMS: During historical yield improvement in soybean, breeders have seldom considered selection for root traits, generally focusing selection on yield traits. Yet, it is not known how root traits of historical cultivars would be altered if their shoot functions and grain yields were largely improved. Here we investigated the influence of record-yield soybean cultivars L14 and Z35 as scions on root traits of historical cultivars. METHODS: A total of 11 cultivars, released in different decades, were used to graft with L14 or Z35 scions. Some morphological and physiological traits were measured in the pot-culture experiments. RESULTS: During grain-filling stage, the scions of L14 and Z35 had greater photosynthetic capacity, seed biomass and seed starch accumulation than those of other cultivars. Grafting of cultivars with L14 and Z35 scions resulted in significant decreases in root biomass, root-shoot ratio, root starch accumulation and root morphological traits compared with non-grafts or self-grafts. The genetic gain for these root traits of cultivars released from 1966 to 2006 increased by grafting record-yield cultivars scions, while that of grain yield and nutrient accumulation decreased. CONCLUSIONS: Our results revealed the uncoordinated improvement between roots and shoots during historical breeding in soybean.