Soybean cyst nematode (NCS), Heterodera glycines Ichinohe, is one of the main crop pests, due to the damage it can cause and the enormous ease of dissemination and ability to survive in the soil. It was detected in Brazil for the first time in the 1991/1992 harvest. It is currently present in 10 states (Minas Gerais, Mato Grosso, Mato Grosso do Sul, Goiás, São Paulo, Paraná, Rio Grande do Sul, Bahia, Tocantins and Maranhão). However, there are still many properties free from the pathogen, located in municipalities considered infested. Therefore, prevention remains important. This practice also helps to prevent the introduction of new breeds into already infested properties.
The spread of NCS occurs mainly through the transport of infested soil. This can occur through agricultural equipment, poorly processed seeds that contain soil particles, wind, water and even birds that, when collecting food from the soil, can ingest the cysts together. It is important to raise awareness among producers about the need to clean agricultural equipment after it has been used in other areas, to avoid contamination of the property. The transit of machinery, equipment and vehicles has been the main agent for dispersing the pathogen in the country. Growing perennial grasses (pasture or other) in a small strip on each side of the road can delay the introduction of NCS to nearby crops. The acquisition of processed seeds, free from soil particles, is also essential to prevent the entry of nematodes. Within the property, the spread of NCS can be reduced by adopting direct seeding.
NCS penetrates the roots of the soybean plant and hinders the absorption of water and nutrients. Symptoms appear in reboleiras (Photo 1) and their intensity varies according to the type of soil, the susceptibility of the soybean cultivar used and the population density of the parasite in the soil. In general, it causes reduced size and number of pods, chlorosis and low productivity. In many cases, parasitized plants end up dying. The root system is reduced and infested by tiny female nematodes (Photo 2). These females have a slightly elongated lemon shape. Initially they are white in color and later acquire a yellow color. After being fertilized by the male, each female produces 100 to 250 eggs, storing most of them inside her body. When the female dies, her body transforms into a hard structure called a cyst (Photo 3), dark brown in color, full of eggs (Photo 4), highly resistant to deterioration and desiccation and very light, which detaches from the root and goes to the ground. The cyst can survive in the soil, in the absence of a host plant, for more than eight years. Therefore, it is practically impossible to eliminate the nematode in the areas where it occurs. In moist soil, with temperatures of 20 oC to 30 oC, the second stage juvenile (Photo 5) hatches and, if it finds the root of a host plant, penetrates and the cycle is completed in three to four weeks. The range of host plant species for NCS is limited, with soybean (Glycinemax), beans (Phaseolus) and lupine (Lupinus albus). Most cultivated species, such as corn, sorghum, rice, cotton, sunflower, castor beans, sugar cane, wheat, as well as other grasses, do not multiply it. NCS also does not reproduce in the most common weeds in Brazilian soybean crops.
When the NCS appeared in Brazil, the losses it caused in soybean production were very high. In some cases, they reached 100%. Currently, due to the use of crop rotation and, mainly, due to the use of resistant cultivars, they have been much lower. In each harvest, they can be estimated at around 5%-10%.
In general, replacing soybeans, in a summer crop, with a non-host species (corn, cotton, rice, among others) provides a reduction in the nematode population in the soil sufficient to guarantee the cultivation of susceptible soybeans for another year. However, the rotation must continue in sequence, as the population grows again at risk levels. In the case of summer cultivation for two or more consecutive years with non-host species, as long as the soil pH is at the levels indicated for the region, in most cases, susceptible soybeans can be cultivated in the area in the following two years, without risk of loss. In this case, as a safety measure, it is recommended to carry out an assessment of the cyst population in the soil before the second soybean cultivation. Regarding winter cultivation, in areas infested by NCS, it is recommended to use only non-host plant species (grasses, crucifers, sunflowers, mucunas, sunn hemp, etc.). The cultivation of host species in winter, such as soybeans, beans, lupins, etc., keeps the nematode population high. NCS reproduces in soybeans germinated from grains lost during harvest (“guaxa” or “tiguera” soybeans), increasing the inoculum for the next harvest. Therefore, the presence of “tiguera” should not be allowed in infested areas, a practice also required to comply with the sanitary void.
When NCS was detected in Brazil, all soybean cultivars in use, except ‘IPAGRO 21’, were susceptible. The IPAGRO 21 cultivar, despite being resistant, was not adapted for cultivation in infested areas (Minas Gerais, Goiás, Mato Grosso and Mato Grosso do Sul). To further face this challenge, public and private soybean genetic improvement companies had to resort to North American soybean germplasm and began to include NCS resistance genes in “elite” Brazilian cultivars. Five years later, the first resistant cultivar (BRSMG Renascença) was released for cultivation in Minas Gerais. Subsequently, BRSMT Pintado, BRSMT Piraíba, BRSMT Matrinxã, BRSMG Liderança, M-SOY 7901, M-SOY 8001, among others, appeared. Currently, more than 80 resistant soybean cultivars are available (Table 1). However, the genetic variability exhibited by the NCS in the country (breeds 1, 2, 3, 4, 4+, 5, 6, 9, 10, 14 and 14+) greatly hinders the development of such cultivars and also reduces their useful life.
Most NCS-resistant soybean cultivars available in Brazil are only suitable for races 1 and 3. For the Central-West region, where races with a greater number of parasitism genes are frequent (races 2, 4, 5, 6, 9 and 14), there is a lack of resistant cultivars. Even for races 1 and 3, there are no cultivars adapted for all growing regions. There has also been difficulty in obtaining early resistant cultivars, which are generally less affected by Asian rust (Phakopsora pachyrhizi) and that allow a second crop (corn or cotton) in the area. Another major challenge is preserving the resistance of cultivars. With the availability of resistant cultivars, farmers begin to practice monoculture. This enormous selection pressure generated on pathogen populations results in the selection of other races, which “break” the resistance of cultivars. To avoid the problem, the ideal is to adopt a rotation system, which involves non-host crops, susceptible soybeans and resistant soybeans.
Adequate soil management in areas infested with NCS (higher levels of organic matter, base saturation within that indicated for the region, distribution of potassium in sandy soils, balanced fertilization, supplementation with micronutrients and absence of compacted layers) is also important, as it increases the soybean's tolerance to damage and favors the action of the nematode's natural enemies (fungi, bacteria, mites, other nematodes, etc.).
| Table 1. Brazilian soybean cultivars resistant to NCS. Embrapa Soja, May 2015. | ||
| Breeder | Cultivar | Race* |
| Agroeste | AS 3820IPRO | 1,3,6,9 and10 |
| Brasmax | Strong RR | 3 |
| Brasmax | IPRO tip | 3 MR 14 |
| Coodetec | CD 217 | 3 |
| Coodetec | CD237RR | 3 |
| Coodetec | CD242RR | 3 |
| Embrapa | BRS 231 | 1 and 3 |
| Embrapa | BRS 262 | 1 and 3 MR 14 |
| Embrapa | BRS 263 [Different] | 1 and 3 MR 14 |
| Embrapa | BRS 7980 | 1 and 3 MR 5 |
| Embrapa | BRS Invernada | 1 and 3 |
| Embrapa | BRS Jiripoca | 1 and 3 MR 14 |
| Embrapa | BRS 295RR | 1 and 3 |
| Embrapa | BRS 399RR | 3 and 14 |
| Embrapa | BRS 8890RR | 1 and 3 MR 5 |
| Embrapa | BRSGO 7360 | 3 |
| Embrapa | BRSGO Araçu | 1 and 3 |
| Embrapa | BRSGO Chapadões | 1,2,3,4,5,6,9,10 and 14 |
| Embrapa | BRSGO Edeia | 3 |
| Embrapa | BRSGO Ipameri | 3 and 14 |
| Embrapa | BRSGO Raíssa | 1 and 3 |
| Embrapa | BRSGO 7561RR | 1 and 3 |
| Embrapa | BRSGO 8460RR | 1 and 3 |
| Embrapa | BRSGO 8660RR | 3 |
| Embrapa | BRSGO 8661RR | 1,2,3 and 14 |
| Embrapa | BRSGO 8860RR | 3 MR 14 |
| Embrapa | BRSMG 715A | 3,4,4+,6,9,10 and 14 |
| Embrapa | BRSMG 810C | 1 and 3 |
| Embrapa | BRSMG 724CRR | 3 |
| Embrapa | BRSMG 811CRR | 3 |
| Embrapa/Fund. MT | BRSMT Pintado | 1 and 3 MR 14 |
| MT Foundation | FMT Tabarana | 3 |
| MT Foundation | FMT Tucunaré | 1 and 3 |
| FT Seeds | FT Esperança | 1 and 3 MR 14 |
| IAC | Foster | 1 and 3 MR 14 |
| Monsoy | M-SOY 8001 | 1 and 3 |
| Monsoy | M-SOY 8200 | 1 and 3 |
| Monsoy | M-SOY 8757 | 3 |
| Monsoy | M6707RR | 1 and 3 |
| Monsoy | M7639RR | 3 |
| Monsoy | M 7739 IPRO | 1 and 3 |
| Monsoy | M 8133 IPRO | 1 and 3 |
| Monsoy | M 8330 IPRO | 1 and 3 |
| Nidera | The 4725RR | 3 |
| Nidera | NS 7490RR | 3 |
| Nidera | NS 8393RR | 3 |
| Nidera | NS 8490RR | 3 |
| Pioneer | P 98N82 | 3 |
| Pioneer | P 95Y21 | 3 |
| Pioneer | P 95Y51 | 1 and 3 |
| Pioneer | P 95Y72 | 3 |
| Pioneer | P97Y07 | 3 |
| Pioneer | P 98Y11 | 1 and 3 |
| Pioneer | P 98Y12 | 3 |
| Pioneer | P 98Y30 | 3 |
| Pioneer | P 98Y70 | 3 |
| Soy Tech | ST810RR | 1 and 3 |
| Syngenta | NK 7059RR | 3 |
| Syngenta | NK 7074RR | 3 |
| Syngenta | Syn 1157RR | 3 |
| Syngenta | Syn 1180RR | 3 MR 2,4,14 |
| Syngenta | Syn 1182RR | 3 MR 1 |
| Syngenta | Vmax | 3 and 14 |
| Syngenta | Vmax RR | 3 and 14 |
| TMG | TMG 4182 | 1,2,3,4,5,6,9,10 and 14 |
| TMG | TMG 4185 | 1,3,4,6,9,10 and 14 MR 2 and 5 |
| TMG | TMG 113 RR | 3 |
| TMG | TMG 115RR | 1 and 3 MR 14 |
| TMG | TMG 117RR | 1 and 3 |
| TMG | TMG 121RR | 1 and 3 MR 14 |
| TMG | TMG 123RR | 1 and 3 |
| TMG | TMG 132RR | 1 and 3 |
| TMG | TMG 133RR | 1 and 3 |
| TMG | TMG 1168RR | 3 and 14 |
| TMG | TMG 1174RR | 1 and 3 |
| TMG | TMG 1175RR | 1 and 3 |
| TMG | TMG 1176RR | 1 and 3 |
| TMG | TMG 1179RR | 1 and 3 |
| TMG | TMG 1180RR | 3 |
| TMG | TMG 1188RR | 3 and 14 |
| TMG | Tapir 82RR | 3 MR 14 |
| TMG | TMG 2181IPRO | 3 |
| Military man | W 831 | 3 |
| Military man | W 851 | 3 |
| Military man | W 855 | 3 |
| Military man | W 888 | 3 |
| Military man | W 901 | 3 |
Table 1. Brazilian soybean cultivars resistant to NCS. Embrapa Soja, May 2015.
Breeder
Cultivar
Race*
Agroeste
AS 3820IPRO
1,3,6,9 and10
Brasmax
Strong RR
3
Brasmax
IPRO tip
3 MR 14
Coodetec
CD 217
3
Coodetec
CD237RR
3
Coodetec
CD242RR
3
Embrapa
BRS 231
1 and 3
Embrapa
BRS 262
1 and 3 MR 14
Embrapa
BRS 263 [Different]
1 and 3 MR 14
Embrapa
BRS 7980
1 and 3 MR 5
Embrapa
BRS Invernada
1 and 3
Embrapa
BRS Jiripoca
1 and 3 MR 14
Embrapa
BRS 295RR
1 and 3
Embrapa
BRS 399RR
3 and 14
Embrapa
BRS 8890RR
1 and 3 MR 5
Embrapa
BRSGO 7360
3
Embrapa
BRSGO Araçu
1 and 3
Embrapa
BRSGO Chapadões
1,2,3,4,5,6,9,10 and 14
Embrapa
BRSGO Edeia
3
Embrapa
BRSGO Ipameri
3 and 14
Embrapa
BRSGO Raíssa
1 and 3
Embrapa
BRSGO 7561RR
1 and 3
Embrapa
BRSGO 8460RR
1 and 3
Embrapa
BRSGO 8660RR
3
Embrapa
BRSGO 8661RR
1,2,3 and 14
Embrapa
BRSGO 8860RR
3 MR 14
Embrapa
BRSMG 715A
3,4,4+,6,9,10 and 14
Embrapa
BRSMG 810C
1 and 3
Embrapa
BRSMG 724CRR
3
Embrapa
BRSMG 811CRR
3
Embrapa/Fund. MT
BRSMT Pintado
1 and 3 MR 14
MT Foundation
FMT Tabarana
3
MT Foundation
FMT Tucunaré
1 and 3
FT Seeds
FT Esperança
1 and 3 MR 14
IAC
Foster
1 and 3 MR 14
Monsoy
M-SOY 8001
1 and 3
Monsoy
M-SOY 8200
1 and 3
Monsoy
M-SOY 8757
3
Monsoy
M6707RR
1 and 3
Monsoy
M7639RR
3
Monsoy
M 7739 IPRO
1 and 3
Monsoy
M 8133 IPRO
1 and 3
Monsoy
M 8330 IPRO
1 and 3
Nidera
The 4725RR
3
Nidera
NS 7490RR
3
Nidera
NS 8393RR
3
Nidera
NS 8490RR
3
Pioneer
P 98N82
3
Pioneer
P 95Y21
3
Pioneer
P 95Y51
1 and 3
Pioneer
P 95Y72
3
Pioneer
P97Y07
3
Pioneer
P 98Y11
1 and 3
Pioneer
P 98Y12
3
Pioneer
P 98Y30
3
Pioneer
P 98Y70
3
Soy Tech
ST810RR
1 and 3
Syngenta
NK 7059RR
3
Syngenta
NK 7074RR
3
Syngenta
Syn 1157RR
3
Syngenta
Syn 1180RR
3 MR 2,4,14
Syngenta
Syn 1182RR
3 MR 1
Syngenta
Vmax
3 and 14
Syngenta
Vmax RR
3 and 14
TMG
TMG 4182
1,2,3,4,5,6,9,10 and 14
TMG
TMG 4185
1,3,4,6,9,10 and 14 MR 2 and 5
TMG
TMG 113 RR
3
TMG
TMG 115RR
1 and 3 MR 14
TMG
TMG 117RR
1 and 3
TMG
TMG 121RR
1 and 3 MR 14
TMG
TMG 123RR
1 and 3
TMG
TMG 132RR
1 and 3
TMG
TMG 133RR
1 and 3
TMG
TMG 1168RR
3 and 14
TMG
TMG 1174RR
1 and 3
TMG
TMG 1175RR
1 and 3
TMG
TMG 1176RR
1 and 3
TMG
TMG 1179RR
1 and 3
TMG
TMG 1180RR
3
TMG
TMG 1188RR
3 and 14
TMG
Tapir 82RR
3 MR 14
TMG
TMG 2181IPRO
3
Military man
W 831
3
Military man
W 851
3
Military man
W 855
3
Military man
W 888
3
Military man
W 901
3
*Information on cultivar resistance was obtained from publicity materials from respective breeders.
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