Physiological indices of two lines of hyacinth bean (Lablab purpureus (L.) Sweet), MEIDOU 2012 and NANHUI 23, were compared during a progressive course of water-withholding treatments. MEIDOU 2012 was shown to be a superior drought-tolerant genotype. A suppressive subtractive hybridisation library was then constructed by using drought-stressed MEIDOU 2012 roots and sequenced to screen for transcripts with differential abundance variations. In total, 2792 unigenes were assembled from 4064 drought-induced expressed sequence tags. Comparative analysis with other legume genomic sequences, including soybean (Glycine max (L.) Merr.), common bean (Phaseolus vulgaris L.) and lucerne (Medicago sativa L.), was performed, from which 338 unigenes associated with root growth and drought response were identified. Among these unigenes, 27 transcription factors were deduced by functional-domain prediction. The transcription levels of a GRAS and a WRKY transcription factor were confirmed to be responding sensitively to water stresses. Additionally, protein–protein interaction (PPI) networks were predicted for all drought-induced root-related unigenes with different stringency levels. A mitogen-activated protein kinase (MAPK4) and an EF-hand calcium-binding protein (CML24) module were pinpointed to be putative ‘master’ signalling hubs in these PPI networks. Detailed examination of these genomic resources would further reveal key regulators of Lablab drought tolerance.

Improvement of soybean [Glycine max (L.) Merr.] yield and photosynthesis physiology have been achieved over decades of cultivar breeding. Identification of the mechanisms involved in shoot-root interactions would be beneficial for the development of yield improvement breeding strategies. The objectives of this study were to investigate soybean shoot-root interactions with different-year released soybean cultivars and to evaluate their effects on grain yield and yield components. Soybean grafts used in this study were constructed with two record-yield cultivars Liaodou14 (L14) and Zhonghuang35 (Z35) and eleven cultivars released in 1966–2006 from the United States and Chinese. The grafting experiments were conducted as pot-culture experiments and repeated in 2014 and 2015. Our results showed that net photosynthesis rate (P_N) was positively correlated to both root activity and root bleeding sap mass (RBSM) during the R6 reproductive stage. Moreover, different year-released soybean shoots had all exhibited capabilities of changing the root activity and architecture of L14 and Z35 rootstocks to “generation”-specific patterns during all reproductive stages. However, these influences were independent of the photosynthetic strength. Yield analysis had demonstrated that high-yielding root systems (L14 and Z35 rootstocks) could cause more than 15% of yield increase in seven out of eleven common scions in a scion-genotype-dependent manner. For Williams-descendant cultivar scions, L14 and Z35 rootstocks promoted yields mainly by increasing the seed number (SN), but those scions of Amsoy-descendent cultivars showed mainly seed weight (SW) increases when grafted onto L14 and Z35 rootstocks. On the other hand, although most tested common rootstocks did not show significant influence over the final yields in record-yield L14 and Z35 scions, they were obviously capable of shifting the formation of yield components when compared to L14 and Z35 self-grafting controls. Taken together, soybean shoots could influence the root physiology and played a crucial role in the determination of yield potentials. Synergistically with shoots, soybean roots played a more supportive role during the realization of yield potentials through root activities and by balancing the formation of yield components. These findings provided interesting insightful information for developing new breeding strategies which aim to pyramid elite physiological and yield traits by selecting specific parental combinations.

Understanding the genetic basis of leaf sucrose content can provide a novel way in improving soybean yields. To identify the related QTLs, 190 materials of chromosome fragment substitution lines (CSSLs) were used in this study. The CSSLs were developed from the cross between the cultivated soybean Suinong 14 (SN14) and wild soybean ZYD00006. Only one QTL with a high logarithm of odds (LOD) score was detected in 2021 and 2022 among 3780 bin markers (combined by 580,524 SNPs) distributed in 20 chromosomes. Nine candidate genes were screened and Glyma.14G029100 was considered as the hub gene. A promoter difference and CDS mutant was found among the parents and the reference genome, which lead to the relative transcriptional level difference.. Our results lay the groundwork for further research into its genetic mechanism.