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Acta Agronomica Sinica ›› 2022, Vol. 48 ›› Issue (3): 565-571.doi: 10.3724/SP.J.1006.2022.14011


Improving seed number per pod of soybean by molecular breeding based on Ln locus

DU Hao1(), CHENG Yu-Han2, LI Tai1, HOU Zhi-Hong1, LI Yong-Li1, NAN Hai-Yang1, DONG Li-Dong1, LIU Bao-Hui1, CHENG Qun1,*()   

  1. 1School of Life Sciences, Guangzhou University, Guangzhou 510006, Guangdong, China
    2Beijing International Urban Agricultural Science and Technology Park, Zhong-Nong-Fu-Tong, Beijng 100083, China
  • Received:2021-01-19 Accepted:2021-06-16 Online:2022-03-12 Published:2021-07-13
  • Contact: CHENG Qun E-mail:duhao990303@163.com;chengqun0118@gzhu.edu.cn
  • Supported by:
    National Natural Science Foundation of China(32001508);National Natural Science Foundation of China(31930083);National Natural Science Foundation of China(31801384)


Molecular design breeding is one of the important methods to combine molecular genetics with conventional breeding, and to breed a series soybean variety with excellent traits. Although this method can shorten the breeding process to a large extent, it is rarely used in the artificial breeding process. Increasing production is one of the most important goals in the process of soybean breeding. Soybean is a typical short-day bean plant, which provides more than a quarter of plant protein for human and animals in the world. In the process of soybean breeding, increasing the yield is one of the main breeding objectives, among which the number of seeds per pod is one of the key traits to determine the yield per plant. In soybean, the number of seeds per pod was positively correlated with leaf shape, which was controlled by an allele Ln/ln. The broad leaflet (Ln) usually linked with no 4-seed pod, and narrow leaflet (ln) associated with 4-seed pod. Although Ln was potentially important for soybean yield, whether this locus could be used in molecular breeding had not been reported. In this study, we found that the narrow leaflet variety was always in high latitude, and the broad leaflet variety in low latitude. To improve soybean yield in low latitude, we developed the molecular marker of Ln. ln was substituted into broad leaflet varieties Willams 82 and Huaxia 3 by backcrossing. Our data provide an important theoretical and practical basis for molecular design breeding to improve soybean yield.

Key words: soybean, Ln, yield, the number of seeds per pod, molecular design

Fig. 1

Geographical distribution of different alleles of Ln variation A: the geographical distribution of Ln variation in China, red for Ln, blue for ln; B: the allele frequency of Ln in different regions. HR: Huanghuai region; NR: Northern region; SR: Southern region; NE: Northeast region."

Fig. 2

Leaf phenotypes of different soybean varieties A: the phenotype of DN50, SN14, HH43, SN88 leaves, the yellow lines represent the leaf width and the red lines represent the leaf length; B: the phenotype of HX3, HX5, BR21, and W82 leaves; bar: 1 cm; C: the length-width ratio of different leaves."

Table 1

Number of pod from 1-seed to 5-seed"

1-seed pod number
2-seed pod number
3-seed pod number
4-seed pod number
5-seed pod number
DN50 6±0.33 12±0.25 23±0.19 25±0.08 0
SN14 9±0.23 15±0.24 20±0.26 25±0.16 0
HH43 11±0.33 15±0.19 28±0.32 29±0.45 1±0.94
SN88 5±0.14 14±0.27 23±0.35 26±0.12 0
HX3 16±0.12 60±0.44 35±0.28 0 0
HX5 22±0.34 54±0.41 34±0.42 0 0
BR21 24±0.12 43±0.25 59±0.34 0 0
W82 18±0.32 39±0.32 61±0.83 2±0.88 0

Fig. 3

Electrophoresis of molecular makers of Ln A: the detection results of Ln. M: DL2000 maker; 1: the digested product of Ln; 2: the digested product of ln; 3: the digested product of Ln heterozygous. B: The genotype of Ln in different cultivars. 1-4: HX3, HX5, BR21, and W82; 5-8: DN50, SN14, HH43, and SN88; 9: the genotype of hybrid between W82 and HH43; 10: the genotype of hybrid between HX3 and HH43."

Fig. 4

Phenotype of ln mutant A: the phenotype of W82 and W82-ln leaves; B: leaves length-width ratio of W82 and W82-ln; C: the phenotype of HX3 and HX3-ln leaves; D: leaves length-width ratio of HX3 and HX3-ln; E: pod types occurring in W82 and W82-ln and pod types occurring in HX3 and HX3-ln, * represents the main type of pod number in the variety; F: total pod number of W82 and W82-ln; G: 4-seed pod number of W82 and W82-ln; H: grain weight per plant of W82 and W82-ln; I: total pod number of HX3 and HX3-ln; J: 4-seed pod number of HX3 and HX3-ln; K: grain weight per plant of HX3 and HX3-ln. **: P < 0.01."

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