Abstract:

Photosynthesis plays an important role in determining crop’s yield. Photosynthetic gas-exchange parameters have been widely used to reflect the photosynthetic capacity of plant. The present study was conducted to identify QTLs associated with gas-exchange parameters in soybean. Pot experiments were carried out in two successive years to evaluate 184 recombinant inbred lines (RILs) derived from a cross between Kefeng 1 and Nannong 1138-2 for photosynthetic rate, stomatal conductance, intercellar CO₂ concentration and transpiration rate at R6 growth stage. The RILs showed transgressive segregation for these parameters, their broad heritability was lower-middle, ranging from 0.48 to 0.60, and significant correlations were observed among them. In total, fifteen QTLs located on seven linkage groups (LG) were identified, six of which expressed stably in two environments. The percentage of variation explained by these QTLs ranged from 4.80% to 12.30%, and with LOD scores from 2.25 to 6.31. Three QTLs for photosynthetic rate were placed on LG C1, E and O respectively, among which the QTL qPnC1.1 (flanked by markers sat_311 and sct_191) was detected in both years; four QTLs for stomatal conductance were placed on LG C1, D2, E and I, respectively, among which QTLs qSCD2.1 (flanked by sat_296 and sat_277) and qSCI.1 (flanked by satt726 and satt330) expressed stably in both years; five QTLs for intercellular CO₂ concentration were placed on LG C1, D2, E, I and O, respectively, among which QTLs qCiI.1 (flanked by satt726 and satt330) and qCiO.1 (flanked by satt94 and sat_291) were detected in both years; three QTLs for transpiration rate were placed on LG C2, H and O, respectively, among which QTL qTrO.1 (flanked by BE801128 and satt345) was detected in both years. It was found that in many cases some QTLs for different traits were located in the same regions of LG. A total of four genomic regions were detected controlling different parameters: the marker interval sat_311–sct_191 on LG C1 for photosynthetic rate and stomatal conductance simultaneously, with positive alleles from Nannong 1138-2; the marker interval sat_172–satt268 on LG E for photosynthetic rate, intercellular CO₂ concentration and stomatal conductance simultaneously, with positive alleles from Kefeng 1; the marker intervals sat_296–sat_277 on LG D2 and satt726–satt330 on LG I for stomatal conductance and interncellular CO₂ concentration simultaneously, with positive alleles from Nanong 1138-2 for the former marker interval, while from Kefeng 1 for the latter one. Compared with other studies, we did not find common QTL that could express stably across different genetic materials, which suggested that the genetic mechanism of photosynthetic gas-exchange parameters is complex in soybean, and further studies need to be performed with more soybean mapping populations in the future.

Key words: Soybean, Photosynthesis, Gas-exchange parameter, RIL population, QTL analysis