The root-lesion nematode (Pratylenchus thornei) is a major pathogen of wheat in the subtropical grain region of eastern Australia. Experiments were conducted to learn whether soil desiccation can account for the rapid fall in peak P. thornei population densities noted in the field after wheat matures. The decline in population densities of P. thornei after growth of wheat was measured on progressive desiccation of soil with roots by fast and slow drying methods. The vertisolic soil of initial moisture content 45% w/w (or matric potential of pF 3.3) was dried in 5% decrements to an air-dried gravimetric moisture content of 15% (pF 5.6) taking 10.7 h for fast drying and 91.5 h for slow drying. After drying, live nematodes were extracted with Whitehead trays for 2 and 7 days and counted in four life stages (adults and juvenile stages J2, J3 and J4). Fast drying resulted in a sigmoidal decline in total P. thornei with only 5% of the population alive in soil at 15% moisture content, but slow drying had no significant effect on the population density. The percentage of nematodes extracted at 2 days compared with the total extracted over 7 days in undried soil (∼89% of total) declined quadratically on desiccation to be 48% (fast drying) and 78% (slow drying) at 15% moisture content. With fast drying, the proportion of adults and J2 decreased whereas the proportion of J4 increased as the soil dried. With slow drying, the proportion of J2 and J3 stages decreased while the proportion of J4 increased. Thus the J4 or pre-adult was the life stage most tolerant of soil desiccation. Time is required for P. thornei to go into a state of anhydrobiosis as a soil dries and this information can be used to model P. thornei survival in the field based on environmental parameters.
Chickpea (Cicer arietinum) is a major legume crop, with Australia being the second largest producer worldwide. Pratylenchus neglectus is a root-lesion nematode that invades, feeds and reproduces in roots of pulse and cereal crops. In Australia, chickpea and wheat (Triticum aestivum) are commonly grown in rotation and annual damage by P. neglectus accounts for large economic losses to both crops. Cultivated chickpea has narrow genetic diversity that limits the potential for improvement in resistance breeding. New collections of wild chickpea species, C. reticulatum and C. echinospermum, have substantially increased the previously limited world collection of wild Cicer germplasm and offer potential to widen the genetic diversity of cultivated chickpea through the identification of accessions with good resistance. This research assessed 243 C. reticulatum and 86 C. echinospermum accessions for response to P. neglectus in replicated experiments under controlled glasshouse conditions from 2013 and 2014 collection missions that were received, tested and analysed in two experimental sets.Multi-experiment analyses showed lower P. neglectus population densities in both sets of wild Cicer accessions tested than Australia's elite breeding cultivar PBA HatTrick at the significance level p < 0.05. Provisional resistance ratings were given to all genotypes tested in both experimental sets, with C. reticulatum accessions CudiB_008B and Kayat_066 rated as resistant in both Set 1 and Set 2. New sources of resistance to P. neglectus observed in this study can be introgressed into commercial chickpea cultivars to improve their resistance to this nematode.
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