ITEMS FROM CANADA

MANITOBA

AGICULTURE AND AGRI-FOOD CANADA

Cereal Research Centre, 195 Dafoe Rd, Winnipeg, Manitoba, Canada, R3T 2M9.

 

Some characteristics of AC Elsa spring wheat reselected for improved tolerance (SuperElsa) to wheat streak mosaic virus. [p. 39-41]

Steve Haber, Ron DePauw, Julian Thomas, and John Noll; and Dallas L. Seifers, Kansas State University, Hays, KS.

As reported here last year (Haber and Seifers 2001), SuperElsa (an unofficial, internal designation) was selected as an apparently true-breeding line from individual AC Elsa plants that had responded with very mild symptoms to seedling infection with WSMV.

Back-assay titrations (Table 1) were used to determine whether improved tolerance or resistance (or both) were associated with superior performance in SuperElsa under WSMV disease pressure. SuperElsa sustained higher infectious virus titres at 18 C than did AC Elsa, even though it had markedly milder symptoms and smaller losses (Fig. 1; Haber and Seifers 2001). At 24 C, by contrast, SuperElsa sustained lower infectious virus titres than AC Elsa. Thus, SuperElsa appeared to combine greater tolerance at 18 C with greater resistance at 24 C. Indeed, in contrast to all other lines tested so far (Table 1; Haber and Seifers 2001), SuperElsa appeared to have the unusual trait of being more resistant (sustaining lower titres of infectious virus) at 24 C than at 18 C (Seifers et al. 1995).

Table 1. Back-assay titration to susceptible Tomahawk winter wheat test seedlings to determine relative levels of infectious virus.
 Dilution of infectious sap  Laura (suseptible check)  Pai Toborichi (tolerant check)  AC Elsa  AC Elsa (reselected line)  KS95H103 (Wsm1 source)
 Infectious titre at 18 C; mean number (three trials) of infected test plants / 10.
 25  5.6  10.0  4.3  6.7  0.0
 50  6.8  9.7  5.3  7.2  0.0
 100  4.2  6.8  4.8  6.9  0.0
 200  3.1  4.2  1.7  5.3  0.0
 400  1.2  1.4  2.3  4.1  0.0
 800  0.9  0.6  1.4  0.6  0.0
 1,600  0.3  0.3  0.0  0.3  0.0
 3,200  0.3  0.0  0.0  0.3  0.0
  Infectious titre @ 24 C: mean number (three trials) of infected test plants / 10
 25  9.1  9.0  6.8  5.8  10.0
 50  7.8  8.9  7.9  5.7  9.7
 100  6.7  8.2  7.0  5.5  9.6
 200  3.4  4.5  4.7  2.5  8.9
 400  2.8  3.4  4.7  0.9  5.8
 800  1.9  0.3  1.3  0.4  4.5
 1,600  0.3  0.9  0.3  0.0  2.1
 3,200  0.0  0.0  0.0  0.0  1.0

In the first year of agronomic trials (conducted at Swift Current and Indian Head, Saskatchewan, and Morden, Manitoba) SuperElsa performed much like AC Elsa in the absence of WSMV disease pressure (Table 2a). Agronomic traits such as height, lodging, maturity, yield, and test weight were similar. Mean seed size (1000-kernel weight) was similar for AC Elsa and SuperElsa when averaged for the three sites but the TKW of SuperElsa varied less among the test sites than did that of AC Elsa or the other tested lines (Table 2b). Seed harvested from the Swift Current site was analyzed for cereal-quality parameters, and this initial analysis (Table 2c) indicated that SuperElsa had acceptable quality traits.

Table 2a. Agronomic traits of SuperElsa compared with AC Elsa and selected Canada western red spring wheat checks.
 Genotype  Mean relative yield (3 sites) *  Relative maturity (3 site mean) **  Relative height (3 sited mean) ***
 SuperElsa  95.2  3.5  2.8
 AC Elsa  96.4  3.5  3.0
 AC Barrie  99.6  4.8  3.3
 AC Cora  90.6  3.0  3.0
 AC Cadillac  90.6  4.5  3.8
 AC Superb  101.7  3.8  3.0
 * Grain yield based on an moving mean and adjusted for control varieties and
replication effect.
** Time to maturity rated on a scale of 1 (very early) to 6 (very late).
*** Plant height rated on a scale of 2 (short) to 6 (tall).

Table 2b. Characteristics of harvested seed of SuperElsa compared with AC Elsa and selected Canada western red spring wheat checks. TKW = 1,000-kernel weight.
 Genotype
 Swift Current
TKW (g)
 Indian Head
TKW (g)
 Morden
TKW (g)
 3-site mean
TKW (g)
 Test weight
3-site mean
(kg/hl)
 SuperElsa  27.0  27.8  27.5  27.3  74.7
 AC Elsa  28.3  34.0  28.0  29.6  74.4
 AC Barrie  31.7  35.3  26.7  31.4  75.3
 AC Cora  26.9  31.4  23.9   27.2  73.0
 AC Cadillac  33.3  37.0  28.6  33.0  77.0
 AC Superb  35.1  40.3  29.1  34.9  75.6

Table 2c. Quality traits of SuperElsa compared with AC Elsa and selected Canada western red spring wheat checks (data only from Swift Current).
   Genotype    Flour yield (%)  Protein (%)  Mixograph dough-quality parameters
 Mixing development time  Peak height  Peak bandwidth energy  Total energy  Bandwidth energy
 SuperElsa  70.7  15.6  2.0  0.199  0.131  55.5  31.0
 AC Elsa  69.9  15.3  2.1  0.161  0.097  48.4  30.7
 AC Barrie  72.3  15.4  2.1  0.191  0.100  57.0  27.9
 AC Cora  68.0  15.0  2.3  0.163  0.089  49.2  26.6
 AC Cadillac  71.0  14.8  2.1  0.187  0.111  51.6  28.9
 AC Superb  70.7  14.8  2.2  0.188  0.100  55.5  27.1

To determine if SuperElsa had arisen from AC Elsa by a fortuitous out-crossing event or seed mixture, these two lines were compared by an AFLP analysis (Fig. 2). The pattern of bands in SuperElsa did not show clear differences from that of AC Elsa with the exception of one band at ~ 130 bp; this band was present in AC Elsa and absent in SuperElsa.

We now are examining the inheritance of tolerance/resistance in SuperElsa and how it interacts with other sources of resistance. Larger-scale field experiments followed by assessments of grain quality will determine if SuperElsa might provide effective protection in the near term against severe losses from WSMV outbreaks.

References.