Distribution and Virulence Phenotypes of Soybean Cyst Nematode (Heterodera glycines) based upon Host Differentials in Jilin Province

 

Xiujuan Yan1,2, Jinwen Liu2, Mingshu Li2, Qiang Qiu2, Xiaofeng Zhu1 and Yuxi Duan1*

1Nematology Institute of Northern China, Shenyang Agricultural University, Shenyang 110161, China

2Soybean Research Institute, Jilin Academy of Agricultural Sciences Changchun 130124, China

*For correspondence: duanyx6407@163.com

Contributed equally to this work and are co-first authors

Received 02 December 2020; Accepted 18 December 2020; Published 25 January 2021

 

Abstract

 

Jilin is the dominant soybean production province in China. Soybean cyst nematode [Heterodera glycines] (SCN) is one of the most important yield-limiting factors in soybean production. Information about the distribution and virulence phenotypes of SCN in soybean fields are essential for optimizing varieties choice in the region. The distribution and virulence phenotypes of SCN in 141 soil samples from 38 cites (cities, counties and towns) across Jilin province were investigated. One hundred and four (73.76%) of the samples from all 38 cities (counties, towns) tested positive for SCN and SCN population densities were more than 5 cysts/100 mL soil in 53 samples from 27 cities (counties, towns). In those 53 samples, we identified 7 races and 12 Heterodera glycines (HG) types, with Race 3 and HG Type 7 being the most dominant genotypes. Of all the genotypes identified, Race10 and HG Type 1.7 were found for the first time in China, and HG Type 3.4.5.7 was the first reported worldwide. Thirty-eight SCN populations (34.5%) were virulent on plant introduction (PI) 548316 (#7) and 15 of them had female indices (FI) ≥ 10% on Pickett. PI 548316 and Pickett were not recommended as parents of breeding against cyst nematode in Jilin province. Peking-type resistance sources were preferred to pi88788-type in Jilin province. In addition, it was found neither the race nor HG scheme is sufficient for differentiating SCN populations in Jilin province, nor the combination of the two methods is recommended for studying the genetic diversity of SCN in Jilin province. That is, Pickett which was removed in HG scheme should be included not as an indicator line but just to separate different races from the same HG type. © 2021 Friends Science Publishers

 

Keywords: Parasite; Virulence phenotypes; Cyst isolation

 


Introduction

 

Soybean cyst nematode (SCN) is an obligate parasite, and its host specialization is obvious. The diversity of SCN is evaluated either by the race determination scheme (Golden et al. 1970; Riggs and Schmitt 1988) or HG Type classification scheme (Niblack et al. 2002).

The Race determination scheme was developed in 1970 (Golden et al. 1970); where four differential soybean lines including Pickett, Peking, PI 88788 and PI 90763 and the susceptible cultivar Lee 68 was used to characterize the heterogeneity of H. glycines. Based on this scheme, 16 potential races were proposed (Riggs and Schmitt 1988). Currently, it had become international scheme for classifying H. glycines virulence. Of the 16 races, race 11 and race 13 have not been found yet, and race 16 was reported only once. There are 13 races in the United States, including race 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14 and 15 (Kim et al. 1997; Xu et al. 2010). Nine races 1, 2, 3, 4, 5, 6, 7, 9 and 14 had been found in China with 1, 3 and 4 being the most widely distributed (Song et al. 2016). In 2017, a new SCN population (called race X12) was detected in Shanxi province, China (Lian et al. 2017). With more and more new SCN populations identified and reported, the race scheme became not sufficient to classify the virulence profile in SCN. Therefore, a new scheme for the virulence phenotype-HG Type classification was proposed (Niblack et al. 2002). HG Type testing enables more accurate management recommendations than the Race scheme does (Winter et al. 2006). Since the scheme was formally proposed at the national soybean cyst nematode conference in 2008, it has been widely accepted and used. Virulence phenotypes of H. glycines had been surveyed with HG Type in some U.S. states (Niblack et al. 2003; Zheng et al. 2006; Mitchum et al. 2007; Colgrove and Niblack 2008; Rzodkiewicz 2010; Acharya et al. 2016; Howland et al. 2018) and also in Korea (Kim et al. 2013). In China, the race scheme has always been used, and the application of HG scheme is relatively less (Wang et al. 2014; Chen et al. 2015; Cui et al. 2018).

In China, most soybeans are produced in Jilin province and the SCN disease spreads widely in this area. The lack of distribution and phenotypic diversity surveys hinder the efficient management of SCN. The only study on the distribution of SCN in Jilin province was reported in 1988 (Liu and Wu 1988); In the past 30 years, there was no report about SCN distribution and genetic diversity of SCN population in Jilin Province, which seriously restricted the progress of soybean resistance breeding against cyst nematode. There are only a few resistant varieties bred from limited resistant sources available on the market, e.g., Bainong 8, Bainong 9 and Bainong 10 derived from Peking. Once SCN disease breaks out, only a few resistant varieties would not be enough.

The objective of this study is to determine the distribution, density, as well as the diversity of virulence phenotypes of H. glycines in Jilin province, thus to provide theoretical foundation for introducing and breeding suitable resistant varieties in the region.

 

Materials and Methods

 

Soil sample collection

 

Soil samples were collected from soybean fields in Jilin province. A total of 141 fields from 38 cities (counties, towns) were sampled after harvest (Table 1) via multi-point random sampling within the circumference of the soybean roots. The soil samples were divided into two parts, one for counting to determine the density of the cysts, the other were planted with the SCN-susceptible soybean Jiyu 86 to increase population densities for studying virulence phenotypes of SCN.

 

SCN populations

 

Soil samples with population of more than 5 cysts/100 mL soil were further tested for distribution of virulence phenotypes by race scheme and HG Type scheme.

 

Soybean differential lines

 
The four indicator lines Pickett, PI 548402(Peking), PI 88788 and PI 90763 and susceptible cultivar Lee 74 were from Soybean Research Institute, Jilin Academy of Agricultural Sciences. The other indicator lines PI 548402, PI 437654, PI 209332, PI 89772 and PI 548316, were from Nematology Institute of Northern China, Shenyang Agricultural University.
 

Cyst isolation

 

The isolation of cyst was carried out as described previously (Liu 1995). In brief, 100 mL soil sample was mixed in 300 mL water in a 1000 mL measuring cup. Soil suspensions were mixed well by stirring. The floating particles and suspensions were filtered through 180-μm-pore and 450-μm-pore sieves, 3 times. The residue on a 180-μm-pore sieve was rinsed with a fine water flow into a beaker, filtered with a screen cloth, and dried. Each soil sample was prepared 3 times.

 

Preparation of egg suspension

 

Under a stereomicroscope, full cysts were placed in a Petri dish and crushed, releasing eggs and juveniles (J2). The eggs and juveniles (J2) were transferred to a breaker and diluted to a final density of 1×106·L-1.

 

Inoculation

 

Plastic cups (6.4-cm diameter, 17-cm high) with bottom punched were filled with sterilized soil and sand (1: 3). For germination, surface-sterilized seeds of each soybean line were placed on filter paper under dark conditions for 48 h. One 2–3 cm long soybean seedling was then sown into each pre-irrigated plastic cup. After 3 days, a 2-mL egg suspension was injected into a 3-cm hole around the root of the seedling. There were 5 replicate cups for each line. The cups were placed in large plastic boxes according to sample origin and these boxes were placed in a greenhouse at 27–29°C. Plants were watered daily.

 

Microscopic examination

 

After 30–35 days, the tops of the seedlings were removed. The soil and roots in the plastic cups were poured into a pot and then sprayed with a strong stream of water to dislodge the cysts. The cysts were isolated as described above and counted using a stereomicroscope.

 

Identification

 

Virulence differentiation of SCN population was based on the difference in reproductive ability on indicator lines. Based on the average number of cysts formed on the indicator lines, Female Indices (FI) was calculated, FI ≥ 10 meant ‘+’, FI < 10 meant ‘-’. Virulence phenotypes were identified by the race scheme and HG Type scheme. The formula of the female index (FI):

 

 

Statistical analysis

 

The correlation analysis among indicator lines was performed using IBM S.P.S.S. Statistics 21.

 

Results

 

Distribution and Density of SCN in Jilin province

 

Out of the 141 samples, 104 samples from all 38 cities (counties, town) were positive for SCN (73.76%) (Fig. 1). 100% of soil samples from Gongzhuling, Baishan, Yanji, Taonan, Tongyu and other 9 counties (cities) were positive for SCN.

Table 1: Densities of Heterodera glycines in Jilin province

 

Sampling point city (County)

Number of samples

Number of samples with SCN

Effective sample number ( ≥ 5cyst/100 mL soil)

Cyst density

(cysts/100 mL soil)

City

County(town)

 

Baishan

Baishan

5

2

0

0.4

 

Jingyu

2

2

2

15

 

Fusong

4

3

0

1.75

 

Changbai Korean Autonomous County

4

3

1

2

 

Tonghua

Meihekou

3

2

2

12.67

 

Liuhe

3

1

0

1

 

Liaoyuan

Dongliao

3

1

1

1.67

 

Dongfeng

3

1

0

0.67

 

Baicheng

Baicheng

3

3

3

14.67

 

Taonan

4

4

4

36.25

 

Tongyu

3

3

3

18.33

 

Daan

4

3

1

2.5

 

Siping

Gongzhuling

5

5

4

19.8

 

Shuangliao

3

3

3

11.33

 

Lishu

4

3

2

3.75

 

Yitong

4

2

0

1.5

 

Songyuan

Fuyu

4

3

1

2.5

 

Changling

4

3

1

3.25

 

Qian’an

4

3

1

2

 

Jilin

Jilin

2

2

2

15.5

 

Jiaohe

2

2

2

11.5

 

Huadian

4

2

0

1.25

 

Yongji

4

4

2

4

 

Panshi

3

3

3

12.67

 

Yanbian Korean Autonomous Prefecture

Dunhua

6

5

2

3.33

 

Wangqing

4

3

0

1.75

 

Antu

4

3

2

3.75

 

Helong

4

3

1

2.25

 

Yanji

3

3

0

2

 

Tumen

4

4

2

3.5

 

Hunchun

5

3

0

1.2

 

Longjing

3

3

3

13.67

 

Changchun

Yushu

4

2

1

2.25

 

Changchun

4

4

2

4.75

 

Dehui

4

3

0

1.75

 

Nongan

4

3

1

2.75

 

Jiutai

4

1

0

0.25

 

Shuangyang

4

1

1

1.25

 

Total/Average

141

104

53

6.33

 

 

The average cyst density of all soil samples was 6.33 cyst/100 mL. There were more than 10 cysts/100 mL soil in 24 soil samples from 11 cities (counties, towns), especially in samples from the cities of Taonan, Baicheng, Gongzhuling and Jilin, as well as Tongyu county. The cyst density in Taonan county was 28 cysts/100 mL soil. There were more than 5 cysts/100 mL soils in 53 soil samples from 27 cities (counties, towns).

 

Race identification

 

 

Fig. 1: Distribution of soybean cyst nematode (Heterodera glycines) in Jilin province

Virulence phenotypes of 53 populations with more than 5 cysts /100 mL soil were tested by race scheme. Seven races were identified, i.e., 1, 3, 5, 6, 9, 10 and 14 (Table 2). Race 3 was the most widely distributed, accounting for 62.26%, followed by race 1, accounting for 11.32%. Race 5 and 6 accounted for 9.43% respectively. The SCN in one soil sample was race 10, and one was race 14; of these, race 10 was first found in China.

HG Type

 

SCN virulence phenotypes in 53 soil samples with more than 5 cysts/100 mL soil were tested using HG Type scheme. We identified 12 HG Types 0, 2, 2.5, 2.7, 5.7, 7, 1.7, 1.3.7, 1.5.7, 2.4.7, 2.5.7, 3.4.5.7, (Table 2). HG Type 7 and 0 was predominant, accounting for 33.96% and 30.18%. Both HG Type 5.7 and HG Type 2.5.7 accounted for 7.55%. HG Type 2.5 and HG Type 2.7 accounted for 3.77% and 5.66%. The remaining types each accounted for 1.89%. HG Type 1.7 was first time recorded in China and HG Type 3.4.5.7 was the first found worldwide.

Table 2: Virulence phenotypes of Heterodera glycines in Jinlin province

 

 

No.

City

County(town)

Pickett

Peking(1)

PI88788(2)

PI90763(3)

PI437654(4)

PI209332(5)

PI89772(6)

PI548316(7)

Race

HG Type

West

1

Songyuan

Fuyu

3.31

-

2.71

-

1.51

-

0.60

-

5.72

-

7.83

-

0.90

-

6.63

-

3

0

2

Changling

3.55

-

1.66

-

7.58

-

4.98

-

1.90

-

7.82

-

2.61

-

19.67

+

3

7

3

Qian’an

7.47

-

2.67

-

6.93

-

3.47

-

0.80

-

7.73

-

4.00

-

25.87

+

3

7

4

Baicheng

Taonan

41.80

+

3.28

-

2.62

-

25.25

+

13.93

+

11.48

+

3.93

-

29.51

+

10

3,4,5,7

5

Taonan

18.22

+

4.12

-

2.82

-

2.17

-

0.43

-

16.70

+

4.34

-

37.96

+

6

5.7

6

Taonan

1.33

-

2.92

-

2.92

-

4.77

-

4.51

-

0.80

-

2.12

-

7.16

-

3

0

7

Taonan

8.41

-

1.68

-

6.25

-

5.29

-

2.16

-

2.16

-

4.33

-

8.65

-

3

7

8

Tongyu

3.77

-

2.08

-

0.19

-

2.26

-

5.66

-

4.91

-

5.09

-

23.58

+

3

7

9

Tongyu

0.98

-

3.58

-

5.21

-

4.56

-

4.56

-

2.28

-

5.86

-

6.51

-

3

0

10

Tongyu

8.20

-

3.61

-

7.87

-

4.92

-

1.97

-

5.25

-

2.62

-

6.56

-

3

0

11

Baicheng

4.61

-

1.05

-

1.05

-

1.26

-

1.05

-

3.14

-

0.84

-

1.68

-

3

5.7

12

Baicheng

11.78

+

11.36

+

3.93

-

7.02

-

1.45

-

15.50

+

2.48

-

30.37

+

9

1.5.7

13

Baicheng

4.86

-

2.13

-

3.04

-

2.74

-

3.95

-

9.12

-

2.43

-

27.66

+

3

7

14

Daan

14.60

+

2.54

-

12.38

+

1.59

-

0.63

-

13.33

+

4.44

-

20.95

+

5

2.5.7

East

15

Yanbian Korean Autonomous Prefecture

Longjing

13.24

+

11.35

+

1.89

-

2.16

-

1.08

-

1.62

-

0.00

-

13.24

+

9

1,7

16

Longjing

3.27

-

0.30

-

5.36

-

2.38

-

4.76

-

3.27

-

2.68

-

23.21

+

3

7

17

Longjing

2.32

-

0.70

-

3.25

-

2.55

-

2.32

-

2.32

-

2.55

-

3.02

-

3

0

18

Duhua

8.82

-

1.26

-

1.76

-

8.82

-

4.03

-

2.02

-

8.06

-

8.56

-

3

0

19

Duhua

7.21

-

4.08

-

0.31

-

0.94

-

0.00

-

3.45

-

7.21

-

15.05

+

3

7

20

Helong

12.70

+

2.78

-

2.78

-

7.14

-

7.54

-

7.94

-

2.38

-

9.13

-

6

0

21

Antu

11.18

+

13.21

+

4.47

-

12.60

+

3.25

-

7.72

-

6.71

-

34.96

+

14

1.3.7

22

Antu

7.59

-

1.31

-

11.26

+

2.36

-

4.97

-

2.36

-

0.79

-

32.46

+

1

2.7

23

Tumen

12.31

+

2.24

-

19.78

+

5.60

-

2.61

-

28.36

+

4.10

-

16.42

+

5

2.5.7

24

Tumen

0.56

-

2.52

-

3.36

-

2.80

-

4.48

-

5.04

-

4.48

-

15.41

+

3

7

Mid-region

25

Jilin

Jilin

36.04

+

1.90

-

2.17

-

2.44

-

1.36

-

34.42

+

2.17

-

27.37

+

6

5.7

26

Jilin

15.58

+

3.90

-

13.96

+

1.62

-

11.36

+

6.17

-

1.30

-

20.45

+

5

2.4.7

27

Jiaohe

3.27

-

1.76

-

1.01

-

2.26

-

0.75

-

1.01

-

2.76

-

31.91

+

3

7

28

Jiaohe

4.82

-

1.29

-

11.58

+

2.25

-

6.11

-

3.54

-

9.32

-

15.43

+

1

2.7

29

Yongji

7.51

-

3.18

-

2.31

-

4.34

-

2.60

-

8.96

-

2.02

-

6.07

-

3

0

30

Yongji

5.65

-

4.32

-

5.98

-

4.32

-

0.00

-

3.65

-

7.64

-

8.31

-

3

0

31

Panshi

1.61

-

0.64

-

16.40

+

1.29

-

0.64

-

4.82

-

2.89

-

19.61

+

1

2

32

Panshi

6.21

-

3.92

-

0.33

-

3.59

-

3.27

-

1.96

-

3.92

-

26.80

+

3

7

33

Panshi

3.79

-

2.84

-

4.73

-

4.42

-

3.15

-

5.99

-

4.73

-

38.49

+

3

7

34

Siping

Gongzhuling

7.24

-

4.91

-

7.49

-

7.75

-

7.49

-

5.94

-

1.55

-

14.21

+

3

7

35

Gongzhuling

7.07

-

10.61

+

5.14

-

5.47

-

7.07

-

9.32

-

7.72

-

28.94

+

3

7

36

Gongzhuling

3.97

-

3.44

-

4.76

-

3.44

-

4.23

-

6.88

-

7.94

-

9.79

-

3

0

37

Gongzhuling

7.31

-

6.15

-

15.77

+

3.46

-

5.77

-

6.92

-

4.23

-

25.00

+

1

2.7

38

Lishu

6.68

-

1.73

-

3.22

-

3.96

-

2.48

-

14.11

+

3.22

-

21.04

+

3

5.7

39

Lishu

2.25

-

2.46

-

2.66

-

3.89

-

2.25

-

0.41

-

3.69

-

30.12

+

3

7

40

Shuangliao

0.00

-

0.00

-

3.59

-

5.25

-

1.66

-

2.49

-

5.25

-

22.38

+

3

7

41

Shuangliao

0.27

-

0.00

-

2.73

-

6.01

-

1.37

-

3.28

-

2.46

-

3.55

-

3

0

42

Shuangliao

2.30

-

0.29

-

4.02

-

2.30

-

3.45

-

2.01

-

2.01

-

4.02

-

3

0

43

Changchun

Changchun

20.90

+

6.35

-

11.64

+

2.65

-

2.38

-

17.72

+

6.35

-

4.50

-

5

2.5

44

Changchun

3.61

-

4.26

-

6.56

-

4.92

-

7.21

-

9.18

-

4.92

-

33.44

+

3

7

45

Shuangyang

6.39

-

1.53

-

6.91

-

6.91

-

1.02

-

3.32

-

5.12

-

19.44

+

3

7

46

Yushu

2.97

-

2.97

-

6.53

-

4.75

-

1.19

-

7.72

-

5.93

-

6.82

-

3

0

47

Nong`an

12.15

+

0.00

-

3.43

-

4.36

-

0.62

-

4.36

-

4.36

-

7.79

-

6

0

48

Baishan

Jingyu

8.90

-

4.71

-

2.62

-

4.71

-

7.59

-

4.45

-

6.28

-

8.12

-

3

0

49

Jingyu

0.85

-

2.56

-

14.25

+

0.57

-

0.57

-

15.67

+

3.70

-

27.92

+

1

2.5.7

50

Changbai Korean Autonomous

3.77

-

3.77

-

3.19

-

0.00

-

5.80

-

1.45

-

1.74

-

7.25

-

3

0

51

Tonghua

Meihekou

13.33

+

4.67

-

4.00

-

5.33

-

4.00

-

5.67

-

0.33

-

22.00

+

6

7

52

Meihekou

17.59

+

6.19

-

16.29

+

0.98

-

4.89

-

3.26

-

0.33

-

33.55

+

5

2.5.7

53

Liaoyuan

Dongliao

2.67

-

0.00

-

13.07

+

2.67

-

0.27

-

12.27

+

4.27

-

6.40

-

1

2.5

Note: ‘+’: FI ≥ 10; ‘-’: FI < 10.

Virulence of SCN groups on indicator lines

 

33 SCN populations in this study were virulent on PI548316: 62.26% had a FI ≥ 10 on the indicator line (#7), 26.42% FI ≥ 10 on Pickett, 20.75% FI ≥ 10 on PI88788 (#2) and 18.87% FI ≥ 10 on PI209332 (#5). PI89772 had the most resistance: 100% populations had a FI < 10 on the line (#6). 3.78% had a FI ≥ 10 on PI 90763 (#3), PI 437654 (#4) and 7.55% on Peking (#1), (Table 2).

A highly significant positive correlation (P < 0.01) was found between the FI on PI 90763 (#3) and PI 437654 (#4), as were correlations among Pickett, PI 90763 (#3) and PI 209332 (#5). Pickett and PI 437654 (#4) were positively correlated (P < 0.05). PI 88788 (#2) and PI209332 (#5) were also positively correlated (Table 3). Additional correlation was found between Peking (#1) and PI548316 (#7) (Fig. 2).

Table 3: Correlation coefficients among soybean differential lines with resistance to Heterodera glycines based on female indices (FIs) from 53 populations in Jilin province

 

Correlation coefficients

Pickett

Peking

PI88788

PI90763

PI437654

PI209332

PI89772

PI548316

Pickett

1

.254

.038

.479**

.301*

.555**

-.099

.253

Peking

 

1

-.014

.202

.147

.106

.074

.295*

PI88788

 

 

1

-.168

.013

.282*

.002

.114

PI90763

 

 

 

1

.442**

.071

.179

.142

PI437654

 

 

 

 

1

-.098

-.041

.110

PI209332

 

 

 

 

 

1

.015

.224

PI89772

 

 

 

 

 

 

1

-.024

PI548316

 

 

 

 

 

 

 

1

* P < 0.05, ** P < 0.01

 

Table 4: Correspondence between race and HG Type

 

Race

HG Type

1

2

2.4

2.5

2.6

2.7

2.4.5

2.4.6

2.4.7

2.5.6

2.5.7

2.6.7

2.4.5.6

2.4.5.7

2.5.6.7

2.4.5.6.7

2

1.2

1.2.4

1.2.5

1.2.6

1.2.7

1.2.4.5

1.2.4.6

1.2.4.7

1.2.5.6

1.2.5.7

1.2.6.7

1.2.4.5.6

1.2.4.5.7

1.2.5.6.7

1.2.4.5.6.7

3

0

4

5

6

7

4.5

4.6

4.7

5.6

5.7

6.7

4.5.6

4.5.7

5.6.7

4.5.6.7

4

1.2.3

1.2.3.4

1.2.3.5

1.2.3.6

1.2.3.7

1.2.3.4.5

1.2.3.4.6

1.2.3.4.7

1.2.3.5.6

1.2.3.5.7

1.2.3.6.7

1.2.3.4.5.6

1.2.3.4.5.7

1.2.3.5.6.7

1.2.3.4.5.6.7

5

2

2.4

2.5

2.6

2.7

2.4.5

2.4.6

2.4.7

2.5.6

2.5.7

2.6.7

2.4.5.6

2.4.5.7

2.5.6.7

2.4.5.6.7

6

0

4

5

6

7

4.5

4.6

4.7

5.6

5.7

6.7

4.5.6

4.5.7

5.6.7

4.5.6.7

7

2.3

2.3.4

2.3.5

2.3.6

2.3.7

2.3.4.5

2.3.4.6

2.3.4.7

2.3.5.6

2.3.5.7

2.3.6.7

2.3.4.5.6

2.3.4.5.7

2.3.5.6.7

2.3.4.5.6.7

8

3

3.4

3.5

3.6

3.7

3.4.5

3.4.6

3.4.7

3.5.6

3.5.7

3.6.7

3.4.5.6

3.4.5.7

3.5.6.7

3.4.5.6.7

9

1

1.4

1.5

1.6

1.7

1.4.5

1.4.6

1.4.7

1.5.6

1.5.7

1.6.7

1.4.5.6

1.4.5.7

1.5.6.7

1.4.5.6.7

10

3

3.4

3.5

3.6

3.7

3.4.5

3.4.6

3.4.7

3.5.6

3.5.7

3.6.7

3.4.5.6

3.4.5.7

3.5.6.7

3.4.5.6.7

11

1.2

1.2.4

1.2.5

1.2.6

1.2.7

1.2.4.5

1.2.4.6

1.2.4.7

1.2.5.6

1.2.5.7

1.2.6.7

1.2.4.5.6

1.2.4.5.7

1.2.5.6.7

1.2.4.5.6.7

12

1.3

1.3.4

1.3.5

1.3.6

1.3.7

1.3.4.5

1.3.4.6

1.3.4.7

1.3.5.6

1.3.5.7

1.3.6.8

1.3.4.5.6

1.3.4.5.7

1.3.5.6.7

1.3.4.5.6.7

13

1

1.4

1.5

1.6

1.7

1.4.5

1.4.6

1.4.7

1.5.6

1.5.7

1.6.7

1.4.5.6

1.4.5.7

1.5.6.7

1.4.5.6.7

14

1.3

1.3.4

1.3.5

1.3.6

1.3.7

1.3.4.5

1.3.4.6

1.3.4.7

1.3.5.6

1.3.5.7

1.3.6.8

1.3.4.5.6

1.3.4.5.7

1.3.5.6.7

1.3.4.5.6.7

15

2.3

2.3.4

2.3.5

2.3.6

2.3.7

2.3.4.5

2.3.4.6

2.3.4.7

2.3.5.6

2.3.5.7

2.3.6.7

2.3.4.5.6

2.3.4.5.7

2.3.5.6.7

2.3.4.5.6.7

16

1.2.3

1.2.3.4

1.2.3.5

1.2.3.6

1.2.3.7

1.2.3.4.5

1.2.3.4.6

1.2.3.4.7

1.2.3.5.6

1.2.3.5.7

1.2.3.6.7

1.2.3.4.5.6

1.2.3.4.5.7

1.2.3.5.6.7

1.2.3.4.5.6.7

 

Discussion

 

Fig. 2: Heat map for correlation between indicator lines

 

In a previous survey conducted in 1988, SCN was distributed over 83% of Jilin province, especially in the counties of Zhenlai, Yushu, Tongyu and Jingyu and in Baicheng city (Liu and Wu 1988). A total of 38 (100%) cities (counties, towns) were infested with SCN in this study. Taonan, Baicheng, Gongzhuling, Jilin city and Tongyu county are the hotspots for SCN distribution (Fig. 1), the same as previous survey, except Jilin city. Significantly, SCN was not detected in Jilin and Longjing cities in the survey conducted in 1988 and cyst density of sample from Gongzhuling increased, possibly due to the long-term cultivation of soybeans and the lack of disease resistant varieties in these regions. As shown in Fig. 1, the density of SCN was the highest and widely distributed in the western of Jilin Province, which may be due to the most of saline-alkali land, followed by the middle part, the lowest in the east.

According to similarities of cellular resistance response in tests, soybean resistance to SCN was classified into two main types: the PI 88788-type, including PI 209332 and PI 548316; and the Peking-type, including PI 90763, PI 89772 and perhaps, PI 437654 (Endo 1965; Kim et al. 1987; Halbrendt et al. 1992; Mahalingham and Skorupska 1996). The results of this study are similar to and different from those of previous studies. The resistance of PI 209332 was similar to that of PI 88788 and PI 548316 (Anand 1992). H. glycines reproduction on these three differentials was significantly positively correlated (Zheng et al. 2006; Colgrove and Niblack 2008; Acharya et al. 2016). In this study, PI 209332 (#5) and PI88788 (#2) had positive correlation on FI (P < 0.05), but not PI 548316 (#7) (Fig. 2). What's interesting was that significant correction was found between PI 548316 and Peking in this study. PI 548316, originally assigned to PI88788-type, now was classified into the Peking-type. Differentials PI 90763 (#3) and PI 437654 (#4) exhibited significant positive correlations on FI (P < 0.01), but not Peking. PI 90763 and PI 437654 were not classified into the Peking-type now. An observation of a stage-related effect of resistance on juvenile development supports that the resistance response may be different between the types (Halbrendt et al. 1992). In addition, Pickett is considered to be the progeny of Peking and may carry similar resistance genes. However, in this study, Pickett and PI 90763 (#3), PI 437654 (#4), PI 209332 (#5) were found to have significant positive correlation but not Peking. This result may be due to the high genetic diversity of the field population. Pickett should be used to distinguish the virulence phenotypes of SCN field populations in Jilin province.

Virulence phenotypes of H. glycines populations were evaluated by race scheme and HG Type scheme. A total of 7 races and 12 HG Types were identified, and race 10 and HG Type 1.7 were first recorded in China. In 1988, race 10 was first discovered in Arkansas (Riggs and Schmitt 1988). In 1996, the race was also identified in Ohio (Willson et al. 1996). HG Type 3.4.5.7 was first found worldwide.

If Jilin Province is divided into eastern, western and central regions, race 1, 3, 5, 6 are distributed in all the three regions in common. Race 1 is dominantly distributed in the mid-region, while the other three races are common. Race 9 was found sporadically in the east and west, but not in the central Jilin Province. Race 10 and 14 distributed in one sampling point in the West and East respectively.

A population`s HG Type name can clearly show invalid indicator plants. Any cultivar that has a similar FI ≥10 should not be used in a field that has an H. glycines population that is compatible with that indicator line. In this student (Table 2), due to FI ≥10 on PI 548316 and Pickett in most of populations, the use of PI 548316 and Pickett as resistant parents should be minimized in Jilin province. The use of PI 88788 (#2) should be also reduced in the west. PI 89772, PI 437654 and PI 90763 are better sources for resistance to SCN. Recently, multi resistant varieties, such as Kangxian 3 (Cao et al. 2014), Dongnong L-10 (Wu et al. 2016), ZDD24656, a variety derived from PI 437654 and ZDD2315 (Lian et al. 2017), Andou 162, a descendant of Franklin, Bedford and Hartwig (Wang et al. 2019), Zhonghuang 26 and Zhonghuang 54, varieties derived from PI 437654 (Wang and Wang 2016) can be used as source of resistance.

When comparing the two schemes, the same race corresponded to multiple HG types, e.g., race 3 corresponded to HG Type 7 and HG Type 5.7 in this study. Additionally, the same HG type may also correspond to multiple races, e.g., HG Type 7 corresponded to race 3 and race 6, and HG Type 5.7 also corresponded to race 3 and race 6 in this study. In a previous study (Wang 2015), HG Type 2.7 corresponded to race 1 and race 5. We considered the SCN population with HG Type 2.7 (race 1) in this study was different from the population with HG Type 2.7 (race 5) in the previous study (Wang 2015). Possibly, that was the same as the population with HG Type 2.7 (race 1) in the previous study. In this way, neither scheme could completely distinguish the virulence phenotypes of SCN populations. HG Type testing is internationally accepted because it is relatively accurate and easily expandable as new soybean germplasm is released and deployed (Winter et al. 2006). The resistant line PI 438489B (Yue et al. 2001) was added to the set of differentials used in the HG Type test in 2007 (Mitchum et al. 2007). However, as the number of identified hosts increases, HG type testing will become more complex. Currently, HG Type + Race are used in SCN research fields (Han et al. 2015; Lin et al. 2016).

Although there is no one-to-one correspondence between race and HG type, there are some corresponding relationships (Table 4). Theoretically, 128 HG types are possible with HG Type testing. Each race corresponded to 16 HG types, and each two races corresponded to the same HG type, e.g., race 3 and race 6 corresponded to the same 16 HG Types. Accordingly, in theory, 256 different SCN virulence types are possible with the combination of the two methods, but the lack of characterization of them. More trials are needed for further validation. According to this study, the combination of the two methods was suitable for the study of genetic diversity of SCN in Jilin province. Pickett which was removed in HG scheme should be included not as an indicator line but just to separate different races from the same HG type in Jilin province.

 

Conclusion

 

In this study, 104 soil samples from 38 cites (cities, counties and towns) were positive for SCN across Jilin province 7 races and 12 HG types were identified, with Race 3 and HG Type 7 being the most dominant genotypes. PI 90763, PI 437654 and PI89772 were recommended as excellent sources against cyst nematode. It suggests that Peking-type resistance sources were preferred to pi88788-type in Jilin province. The combination of the race and HG scheme is recommended for studying the genetic diversity of SCN in Jilin province. That is, Pickett should be included not as an indicator line but just to separate different races from the same HG type.

 

Acknowledgement

 

We acknowledge the financial supports of the National Key Research and Development Program of China (Grant No. 2018YFD1000905).

Author Contributions

 

Xiujuan Yan and Yuxi Duan conceived and designed the experiments; Qiang Qiu and Xiaofeng Zhu collected soil samples; Xiujuan Yan, Jinwen Liu and Mingshu Li performed the experiments; Jinwen Liu analyzed the data;Xiujuan Yan and Jinwen Liu wrote the paper.

 

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