Australasian Association of Nematologists

Root lesion nematode 1996: tolerance, resistance and management strategies

Sharyn Taylor, SARDI, Waite Campus, Vivien Vanstone, University of Adelaide, Waite Campus and Andrew Ware, PISA, Minnipa Research Centre

Tolerance and yield loss were determined in field trials by comparing yields in untreated plots with plots treated with nematicide. Resistance to Pratylenchus neglectus was determined in field trials by assessing numbers of nematodes in soil from all plots at sowing and immediately prior to harvest. As the nematicide also acts as an insecticide, all pulse and medic varieties at field sites were sprayed with insecticide during the season to eliminate any effects of insect damage. Data are presented as either nematodes per 200 grams of soil or per gram of soil.

Cereal tolerance/yield loss

A trial was established at Sandilands on Yorke Peninsula (YP) to determine tolerance and resistance of wheat, barley, oat and triticale varieties to P. neglectus. Field pea, faba bean, chickpea, vetch, canola and medic varieties were also included in this trial and will be discussed in the following section. Although initial nematode numbers at the Sandilands site were low (average of one P. neglectus per gram of soil at sowing) a yield loss of 13-17% was observed in the most intolerant wheat varieties Machete, 11/9 and Beulah. Buckley, Franklin, Carrolup, Wallaroo, Ouyen and Yallaroi were moderately intolerant with a yield loss of 9-11%. The most tolerant cereal varieties were Excalibur, Muir, Spear, Trident, Galleon, Chebec, Yanac, Frame, Bettong and Krichauff (Table 1).

In addition to the Sandilands site, two smaller cereal tolerance trials were sown on Upper Eyre Peninsula (EP) by Andrew Ware. One site (Condada) had pure P. neglectus (average of three P. neglectus per gram of soil at sowing) and a second site (Minnipa) had high levels of P. thornei (average of four P. thornei per gram of soil at sowing). The most intolerant varieties at the Condada P. neglectus site were Echidna and Machete with losses of 25% and 21%, respectively. The most tolerant varieties were Excalibur, Krichauff and Schooner (Table 2). Similar rankings were obtained from the Sandilands site, although some exceptions did occur, with Tahara and Echidna having higher yield loss on Eyre Peninsula. Sites and seasonal conditions will affect magnitude of yield loss caused by nematodes.

The most intolerant variety at the P. thornei site was Stiletto with a loss of 14%. Barunga Excalibur, Frame and Krichauff were moderately intolerant. Echidna, Tahara, Potoroo, Chebec and Schooner appeared most tolerant (Table 2). Although Machete appeared tolerant in this trial, previous research has indicated this variety is intolerant to P. thornei. These rankings were different to those obtained for P. neglectus, indicating the variation in tolerance response to the nematode species.

Pulse, oilseed and medic tolerance/yield loss

Some varieties of canola were intolerant, with visual responses observed early in the season, and yield losses of 28% in Karoo and 10% in Rainbow. Narendra, Oscar, the breeders’ lines BLN800 and BLN900 and Hyola 42 were more tolerant (Table 3).

Although pulses were sprayed for Heliothis, a heavy infestation still occurred and yield losses may have been over-estimated especially for faba beans, chickpeas, peas and vetch. The yields of chickpeas were very low at this site, because of contamination with regenerating medic. For these reasons all pulses require further investigation.

Table 1. Yield loss in cereal varieties caused by P. neglectus, Sandilands,
Yorke Peninsula, 1996 (pre-sowing 1 nematode/g soil)

Crop	Variety	Untreated yield (t/ha)	Yield loss (%)		Crop	Variety	Untreated yield (t/ha)	Yield loss (%)
Wheat Wheat Wheat Wheat Barley Oat Oat Wheat Durum Barley Oat Oat Wheat Wheat Wheat	Machete 11/9 Beulah Buckley Franklin Carrolup Wallaroo Ouyen Yallaroi Schooner Echidna Bandicoot Bowie Barunga Tatiara	3.1 3.5 3.4 4.1 3.8 3.2 2.6 3.6 3.2 3.4 3.6 2.5 3.6 2.9 3.5	17 14 13 11 11 11 10 9 9 8 7 7 7 7 6		Triticale Oat Wheat Triticale Oat Wheat Triticale Wheat Wheat Barley Barley Wheat Wheat Oat Wheat	Tahara Euro Janz Abacus Potoroo Excalibur Muir Spear Trident Galleon Chebec Yanac Frame Bettong Krichauff	3.4 3.6 3.8 3.4 4.1 3.8 3.2 4.2 3.6 3.8 3.6 3.2 3.9 3.4 4.1	6 5 4 4 4 3 3 2 0 0 0 0 0 0 0

Table 2. Yield loss caused by P. neglectus (pre-sowing 3 nematodes/g soil) and P. thornei (pre-sowing 4 nematodes/g soil), Upper Eyre Peninsula, 1996.

	P. thornei (Minnipa)		P. neglectus (Condada)
Variety	Untreated yield (t/ha)	Yield loss (%)	Untreated yield (t/ha)	Yield loss (%)
Echidna Machete Janz Tahara Stiletto Chebec BT Schomburgk Euro Potoroo Frame Barunga Excalibur Krichauff Schooner	1.5 1.2 1.3 1.3 1.2 1.2 1.3 1.5 1.7 1.3 1.2 1.4 1.3 1.5	0 1 5 0 14 0 2 5 0 8 9 9 7 0	1.1 1.1 1.2 1.3 1.5 1.3 1.3 1.4 1.5 1.5 1.3 1.5 1.6 1.6	25 21 17 14 11 11 10 9 7 6 5 5 4 1

Table 3. Yield loss in pulse, oilseed and medic varieties caused by P. neglectus, Sandilands, Yorke Peninsula, 1996 (pre-sowing 1 nematode/g soil).

Crop	Variety	Untreated yield (t/ha)	Yield loss (%)		Crop	Variety	Untreated yield (t/ha)	Yield loss (%)
Chickpea Chickpea Faba bean Canola Vetch Pea Chickpea Canola Pea Faba bean Canola Vetch Canola	Amethyst Tyson Ascot Karoo Languedoc Bluey Desavic Rainbow Laura Fiord Dunkeld Blanchefleur Narendra	0.3 0.7 2.2 1.1 1.7 1.4 0.8 1.4 1.8 2.8 1.5 1.5 1.5	43 37 28 27 17 16 14 10 10 9 8 7 7		Canola Chickpea Canola Canola Pea Pea Pea Chickpea Canola Pea Pea Vetch Faba bean	Oscar Kaniva BLN800 BLN900 Early Dun Alma Glenroy Dooen Hyola 42 Bonzer Dundale Popany Icarus	1.7 1.0 1.5 1.7 2.5 2.5 1.8 0.6 1.7 2.0 2.4 1.1 1.7	6 5 5 5 3 2 0 0 0 0 0 0 0

Cereal resistance

Nine wheat varieties were sampled in September/October from SARDI Field Crop Evaluation Secondary and Waite Wheat Breeding trials. Four sites were assessed for P. neglectus and one for P. thornei. Rankings at these sites were similar to those obtained for the Sandilands and Condada sites (Figure 3a). Excalibur, 11/9, Krichauff and RAC655 contained significantly fewer nematodes than Spear or Machete: 64% fewer P. neglectus (Figure 1a) and 58% fewer P. thornei (Figure 1b). P. thornei numbers were much higher than those for P. neglectus.

Figure 1a. Multiplication of P. neglectus on wheat (data from 5 reps at four sites: Streaky Bay, Minnipa, Kalanbi, Walker Flat). LSD 5% = 4.7

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Figure 1b. Multiplication of P. thornei on wheat (data for 5 reps at one site: Nunjikompita).
LSD 5% = 36.1

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Durum varieties and lines from trials established by Brenton Brooks (Waite Wheat Breeding) were assessed for P. neglectus at three sites (Walker Flat, Roseworthy, Minnipa) in September/
October, and values compared with Spear. Durums were similar to Spear, although Kamilaroi contained significantly more nematodes (Figure 2). All varieties hosted similar numbers of nematodes, although further testing is required.

Figure 2. Multiplication of P. neglectus on durum wheat (4 reps at 3 sites). LSD5% = 1.9

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At the Sandilands site, initial P. neglectus numbers were low. Most varieties showed relatively low rates of nematode multiplication and many appeared to reduce P. neglectus numbers from the initial level of one nematode per gram of soil. In general the wheat varieties were the most susceptible, followed by oat and barley varieties. Excalibur and Krichauff wheat and Abacus, Muir and Tahara triticale were the most resistant varieties tested. Rankings from the Condada site were very similar but final nematode levels were much higher (Figure 3a). These rankings support previous research by Vanstone. Samples from the P. thornei site are still to be assessed.

Pulse, oilseed and medic resistance

Most pulse, oilseed and medic varieties showed low rates of nematode multiplication at the Sandilands site. Chickpea and canola varieties were the most susceptible: Desavic supported the highest nematode population, which was equivalent to the highest multiplication in the cereals (Buckley). Of the canola varieties, Hyola 42 had the lowest yield loss (Table 3) but was the most susceptible (Figure 3b) indicating that it is very tolerant. Canola plots will be re-sampled at the start of the 1997 season to determine if nematode levels have decreased over summer as a result of possible biofumigation action of canola roots and stubble break down. Vetch, pea and faba bean varieties were more resistant. With the exception of the medics, these field data support pot tests by Vanstone, indicating that canola, chickpea and vetch are more susceptible than pea or faba bean. Numbers obtained from medics at this site were lower than indicated from previous data, so further field tests are required.

Rotations and management

Rotation trials at Lameroo and Pinnaroo (established by Trent Potter, SARDI, Struan) were assessed for P. neglectus. Chebec barley and Janz wheat were sampled following a range of rotational crops. Cereal grown after faba bean, pea or peaola (poorer hosts to P. neglectus) was infected with 49% fewer nematodes than cereal after medic, chickpea or vetch (which are better hosts). The previous crop had more effect on nematode numbers in the wheat than in the barley, probably as Janz is more susceptible than Chebec (Figure 3a). Final samples from two rotation/tillage trials and two tillage/fertiliser trials on EP are yet to be assessed.

In a P. thornei trial and a P. neglectus trial on EP, the application of high rates of phosphorus (50kg P/ha) to Machete significantly reduced the magnitude of yield loss caused by the nematodes. At the P. thornei site, very high levels of nematodes (pre-sowing 33/gram of soil) caused a yield loss of 33%, which was reduced to 14% (significant at 5% level) with the application of high phosphorus. P. neglectus (pre-sowing 1/gram of soil) caused a 12% yield loss which was reduced to 6% (significant at 5% level) with the application of high phosphorus.

Figure 3a. Multiplication of P. neglectus on cereals, Sandilands (YP) and Upper Eyre Peninsula, 1996. (Sandilands mean of 2 replicates, Eyre Peninsula mean of 6 replicates).	Figure 3b. Multiplication of P. neglectus on pulses, oilseeds and medics, Sandilands, 1996. (Mean of 2 replicates; data for Desavic and Hyola 42 based on one replicate only).

Conclusions

Krichauff, Excalibur and triticales are consistently both more tolerant and more resistant to P. neglectus than other cereals in field trials.

11/9 appears to be more resistant to P. neglectus, although may be relatively intolerant.

Franklin is more susceptible and more intolerant to P. neglectus than other barley varieties.

Frame, Galleon and Chebec appear tolerant to P. neglectus and are recommended where CCN is a problem.

Desavic chickpea and canola varieties appear more susceptible to P. neglectus (although further information on the potential of canola as a biofumigant is required).

For P. neglectus, Karoo was the most intolerant canola and Hyola 42 was the most tolerant.

Faba bean and pea varieties are more resistant to P. neglectus than other crops.

Acknowledgments

This work is supported financially by the Grains Research and Development Corporation. Trials on EP were established, managed and sampled by Andrew Ware and staff at Minnipa Research Centre. Allan Mayfield managed and harvested the trial at Sandilands. The Waite Wheat Breeding Unit assisted with cereal trials, and some samples were assessed from SARDI Field Crop Evaluation trials on EP. Finally, we sincerely thank the many farmers who make land available for field trials.

	January 1997: contents	January 1997: project summaries