ITEMS FROM AUSTRALIA

 

THE UNIVERSITY OF SYDNEY

PBI Cobbitty and Department of Crop Sciences, Private Bag 11, Camden, NSW, 2570; and Sydney, 2006, Australia.

F. Afshari, H.S. Bariana, J. Bell, G.N. Brown, K.S. Gosal, S. Haque, R.A. McIntosh, H. Miah, R.F. Park, C.R. Wellings, and A. Zakeri.

The 1999 wheat crop in Australia was one of the largest on record, despite drought conditions in South Australia. The main problems were failure to reach adequate protein levels for prime hard segregation, the usual spate of frosting and sprouting, higher than usual levels of black point, and a leaf rust epidemic in Western Australia.

Rust pathogenicity surveys.

A leaf rust epidemic in Western Australia caused losses of about A$20 M. This epidemic involved susceptible varieties, and new pathotypes were not involved. In Eastern Australia, considerable rusting of long-season wheats was caused by mutant pathotypes virulent for Lr17b (present in the Australian cultivar Harrier, as well as Norin 10, Brevor 14, and several European wheats and their derivatives) and Lr13. In New South Wales and Queensland, the Lr26-virulent pathotype 1041,2,3,(6),(7),9,11 was common.

A localized stem rust epidemic in Western Australia occurred on certain susceptible wheats and the cultivar Westonia, which has Sr9g. This epidemic was caused mainly by the 'old' pathotype 34-2,7 which is virulent for Sr9g.

Wheat stripe rust occurred in very low levels in Eastern Australia, and reports of concern were limited to a few early flowering fields in Queensland, prior to increases in spring temperatures. Despite this, two isolates of cultures virulent for Yr17 (VPM1), designated 104 E137A- Yr17+, are quite distinctive from the Yr17 pathotype occurring in New Zealand (234 E139A- Yr17+). Several Australian wheats carry Yr17, and at least some may be too susceptible to the new pathotype for continued production; others should have additional adult plant resistance.

The new barley grass stripe rust first identified in 1998 continued to spread throughout most of Eastern Australia. A group of related barleys appear to be moderately susceptible to this rust, and its potential as a barley pathogen must now be addressed. We do not see it as an immediate threat to wheat.

Host resistance studies.

Seedling-resistance genes derived from the Carstens V and Spaldings Prolific stripe rust differentials were located on chromosomes 2A and 2B, respectively. Both the Spaldings Prolific gene and Yr27 (Selkirk gene) show close repulsion linkage with Lr13. Collaborative studies with researchers in Canada have shown that a stripe rust-resistance gene derived from T. vavilovii is Yr10. In this stock, Yr10 is associated closely with a unique gliadin allele.

Germ plasm screening and enhancement.

More than 30,000 lines were tested as seedlings and/or in field tests for all Australian breeding groups. Two generations of backcrossing to a wide range of breeding lines were achieved.

THE UNIVERSITY OF SYDNEY

IA Watson Wheat Research Centre, Narrabri, 2390, NSW Australia.

K. Mrva and Daryl Mares.

Late maturity alpha-amylase (LMA) in wheat.

Some of the Veery lines (CIMMYT) used in breeding programs in Australia are prone to LMA; that is they have unacceptably high levels of alpha-amylase (low falling number) in harvest-ripe grain in the absence of preharvest sprouting. Veery 1, Veery 5, and Veery 7 samples from trials in 1999 had falling numbers less than 260 sec, whereas the other Veery lines and locally adapted cultivars had falling numbers between 350 and 480 sec (Table 1). These results were consistent with previous observations suggesting that Veery 1, 5, and 7 were similar to genotypes such as Spica, Mentana, and Lerma 52, which have low falling numbers over a wide range of environments. These lines contrast with another set of LMA-prone genotypes that produce low falling number only if exposed to cool temperatures during the mid-phase of grain development. This set includes Suneca, derived from Spica, and Kennedy, derived from Veery 5. One explanation for these observations would be that the other parents in the pedigrees of Suneca and Kennedy contribute a gene(s) that modifies the expression of LMA.

Preharvest sprouting.

Sprouting was widespread in New South Wales in 1999 and also affected crops in Queensland and Western Australia. Black point also was prevalent and, as in 1998, we established that grains affected by black point sprouted more readily than sound grains from the same sample. This observation has important implications for the development of tolerant genotypes to screen for sprouting tolerance and sprouting risk assessment.

Crosses between locally adapted cultivars and the white-grained, sprouting-tolerant genotype AUS1408 have produced two groups of genotypes that have different levels of sprouting tolerance. The first group appears to have recovered all the tolerance, or grain dormancy, of AUS1408 and has maintained consistent performance in germination and spike-wetting tests over several seasons. Unfortunately, these lines are susceptible to crown rot and black point, and further work is underway to determine whether any linkage exists. The second group has an intermediate and more variable level of tolerance. Genotypes in this group appear to have lost one of the two major genes controlling dormancy in AUS1408 but, nevertheless, provide some measure of protection, particularly when compared with current Australian commercial cultivars.