scholarly journals Co-Occurrence of Defoliating and Non-Defoliating Pathotypes of Verticillium Dahliae in Field-Grown Cotton Plants in New South Wales, Australia

Plants ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 750
Author(s):  
Duy P. Le ◽  
Aphrika Gregson ◽  
Thao T. Tran ◽  
Rodney Jackson
Keyword(s):  
Verticillium Dahliae ◽  
New South ◽  
New South Wales ◽  
Cotton Production ◽  
Major Constraint ◽  
South Wales ◽  
Cotton Plants ◽  
Pot Trials ◽  
Germination Traits ◽  
Highly Virulent

Verticillium wilt (VW) is a major constraint to cotton production in Australia and worldwide. The disease is caused by a soilborne fungus, Verticillium dahliae, a highly virulent pathogen on cotton. Commonly, V. dahliae is designated into two pathotypes: defoliating (D) and non-defoliating (ND), based on induced symptoms. In the previous two survey seasons between 2017 and 2019, stems with suspected VW were sampled for the confirmation of presence and distribution of D and ND pathotypes across New South Wales (NSW), Australia. A total of 151 and 84 VW-suspected stems sampled from the 2017/18 and 2018/19 seasons, respectively, were subjected to pathogen isolation. Of these, 94 and 57 stems were positive for V. dahliae; and 18 and 20 stems sampled respectively from the two seasons yielded the D pathotype isolates. Two stems from the 2017/18 season and one stem from 2018/19 season yielded both D and ND pathotype isolates. We also successfully demonstrated the co-infection of both pathotypes in pot trials, which was driven predominantly by either of the pathotypes, and appeared independent on vegetative growth, fecundity and spore germination traits. Our study is the first report of the natural co-occurrence of both D and ND pathotypes in same field-grown cotton plants in NSW, to which a challenge to the disease management will be discussed.

Long-term changes in the numbers of Helicoverpa punctigera (Lepidoptera: Noctuidae) in a cotton production landscape in northern New South Wales, Australia

2016 ◽  
Vol 107 (2) ◽  
pp. 174-187 ◽  
Author(s):  
G.H. Baker ◽  
C.R. Tann
Keyword(s):  
New South ◽  
New South Wales ◽  
Habitat Type ◽  
Bt Cotton ◽  
Cotton Production ◽  
Bt Resistance ◽  
South Wales ◽  
Eastern Australia ◽  
Long Term Changes

AbstractTwo noctuid moths, Helicoverpa punctigera and Helicoverpa armigera, are pests of several agricultural crops in Australia, most notably cotton. Cotton is a summer crop, grown predominantly in eastern Australia. The use of transgenic (Bt) cotton has reduced the damage caused by Helicoverpa spp., but the development of Bt resistance in these insects remains a threat. In the past, large populations of H. punctigera have built up in inland Australia, following autumn-winter rains. Moths have then migrated to the cropping regions in spring, when their inland host plants dried off. To determine if there have been any long-term changes in this pattern, pheromone traps were set for H. punctigera throughout a cropping landscape in northern New South Wales from 1992 to 2015. At least three generations of moths were caught from spring to autumn. The 1st generation (mostly spring migrants) was the most numerous. Trap captures varied between sites and decreased in time, especially for moths in the 1st generation. Nearby habitat type influenced the size of catch and there was some evidence that local weather also influenced the numbers of moths caught. There was no correlation between trap catches in the cropping region and rainfall in the inland. In addition, there was little evidence that Bt cotton has reduced the abundance of H. punctigera at landscape scale. The apparent decline in the number of presumably Bt susceptible moths arriving each spring in the cropping regions from inland habitats is of concern in relation to the management of Bt resistance.

Pre-season soil establishment of legume inoculant rhizobia is not effective for the nodulation of lupin and faba bean crops in acidic soils

2001 ◽  
Vol 41 (8) ◽  
pp. 1149 ◽  
Author(s):  
J. Evans ◽  
P. Eberbach ◽  
D. Luckett ◽  
S. Cormack
Keyword(s):  
Faba Bean ◽  
Rhizobium Leguminosarum ◽  
New South ◽  
New South Wales ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Legume Seed ◽  
South Wales ◽  
Pot Trials ◽  
Bradyrhizobium Sp

In soils with a resident population of symbiotically effective rhizobia in sufficient number that legume inoculation is not a requirement for successful legume cropping, greater flexibility may be exercised in the use of legume seed dressings that are toxic to rhizobia. Inoculating crops antecedent to legume crops has been suggested as a method for pre-establishing effective inoculant rhizobia in soil. The extent to which this strategy (pre-inoculation) would remove the need for inoculating legume seed (conventional inoculation) was tested for Bradyrhizobium sp. (Lupinus) and Rhizobium leguminosarum bv. viciae with crops of lupin (Lupinus angustifolius) and faba bean (Vicia faba), respectively. In the glasshouse, in pasteurised sand and red kandosol, the numbers of B. sp. (Lupinus) in the rhizospheres of wheat (Triticum aestivum), canola (Brassica campestris) and clover (Trifolium subterraneum) increased 300–10000-fold over a 14-week period, reaching numbers similar to that achieved on L. angustifolius. These increases were not greatly affected by chemical seed dressings commonly applied to the crops: on wheat, Vincit C and Baytan C; on canola and subterranean clover, Lemat. In the sandy soil, the nodulation of lupin following pre-establishment of rhizobia, drying and mixing of soil, was not improved by conventional inoculation; in the red kandosol nodulation was increased only marginally by conventional inoculation. The results with the glasshouse pot trials warranted further investigation in the field. Under field conditions, when B. sp. (Lupinus) was pre-established with wheat, on a red kandosol in south-western New South Wales, the number of these bacteria surviving in the dry soil at the end of the wheat phase was much lower than in the glasshouse study. In the following season, the nodulation of lupin sown without inoculant, and dependent only on pre-established rhizobia, was significantly reduced, as compared with that on conventionally inoculated lupin. An exception occurred where the lupin was dry-sown 3 weeks before rain, in which case nodulation was comparatively poor even with conventional inoculation. Reduced nodulation was generally consistent with initially fewer rhizobia in the lupin rhizosphere. However, the numbers of rhizobia were eventually similar to those found with conventional inoculation. In the third year, in autumn, B. sp. (Lupinus) was abundant in the soil in all treatments and there were no differences in lupin nodulation between treatments. Similarly, introducing R. leguminosarum bv. viciae on wheat, in an acidic red kandosol in south-western New South Wales, failed to provide as much nodulation of faba bean as was achieved with conventional inoculation. The maximal dry matter of the bean crop was also significantly lower with pre-inoculation as compared to conventional inoculation.

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