Abstract
The life cycle of the soybean cyst nematode lasts approximately 21-24 days at temperatures ranging from 23 °C to 25 °C. Mean temperatures above 25 °C are often found in Goiás State and in other Brazilian regions. Thus, the aim of the present study is to assess the penetration and cycle duration of Heterodera glycines Type 0- (race 3) in nematode-resistant and susceptible soybean cultivars grown in greenhouse under controlled conditions. The study was conducted at soil temperatures ranging from 23.9 °C to 31.1 °C using two soybean cultivars that were assessed in ten different periods; each assessment was conducted in six plants. The herein used soybean cultivars were BRS Valiosa RR and BRSGO 8860RR, which were, respectively, susceptible and resistant to the nematode. Root staining assessments were performed 2, 4, 6, 9, 12, 15, 18, 21, 24 and 30 days after inoculation (DAI). Besides the root staining assessments, the females and eggs were also assessed through extraction using the sieving and flotation method, at the 30th DAI. Heterodera glycines J2 penetration was similar in both the susceptible and the resistant cultivars throughout the assessment period. It indicates that the nematode penetration was not affected by resistance. The Heterodera glycines cycle at soil temperature ranging from 23.9 °C to 31.1 °C and at room temperature ranging from 27.0 °C to 36.3 °C was complete in 15 days, in both the susceptible and the resistant cultivars. A similar number of J2 has penetrated the roots of both cultivars and greater penetration intensity was found from the 6th to the 15th DAI. The peak J3, J4 and female formation period in the resistant cultivar was later than that observed in the susceptible cultivar.
Highlights
The nematode Heterodera glycines Ichinohe (1952), known as soybean cyst nematode, is one of the main pathogens affecting soybean crops in the main countries producing this oilseed
The aim of the present study is to assess the penetration and cycle duration of Heterodera glycines Type 0- in resistant and susceptible soybean cultivars grown in greenhouse under controlled conditions, as a way to help better understanding the soybean cyst nematode behavior under Brazilian climate conditions
Four seeds of soybean cultivars resistant to Heterodera glycines BRSGO 8860RR and susceptible to Heterodera glycines BRSGO Valiosa RR were seeded in previously autoclaved 0.3 liter-capacity ceramic pots containing a mixture of soil and sand at the ratio 1:1
Summary
The nematode Heterodera glycines Ichinohe (1952), known as soybean cyst nematode, is one of the main pathogens affecting soybean crops in the main countries producing this oilseed This nematode was first detected in Brazil in the 1991/92 harvest (Lima et al, 1992; Lordello et al, 1992; Monteiro & Morais, 1992). It is found in approximately 150 Brazilian counties, covering an area bigger than 3.0 million hectares (Dias et al, 2010). In the absence of a host plant, the cyst is able to survive in the soil for more than eight years (Lordello, 1984; Dias et al, 2010; Embrapa, 2011)
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