Oat grain quality (grain weights per 1000 seeds and groat percentages) was found to be an effective measure of the environmental stress imposed on an oat variety at a particular geographical and climatic centre. The results of various oat trials conducted across NSW show that the environment has an effect on the maturation and filling of the oat grain. The results compiled by the Author suggest that northern NSW (i.e. the summer rainfall zone) could be further sub-divided into 5 climatic regions, from east to west, for the purpose of recommending oat varieties. Glen Innes, at an elevation of 1,128m and latitude 29° 42” S. on the New England Tablelands, proved to be the ideal climate for developing high groat percentage and large grain size. A sixth climatic zone, located in Leeton, NSW (uniform rainfall zone), at elevation at 152m and latitude 34° 33” S., was the second most favourable centre, but required irrigation for full grain development.

Introduction

The environment in which oat varieties are bred and tested can have a significant effect on the final grain quality, in terms of weight and groat percentage. Both of these oat grain parameters are critical in determining how the harvested grain crop will be utilised.

High oat grain quality for the farmer means a crop variety that yields high volumetric weight and high groat percentage. The 1000-grain weight, or seed size of an oat variety, can be low if the yield per ha is high. In general, oat cultivars belonging to the Avena sativa group, with high protein percentage, have been lower in grain yield than those with medium to low protein (Frey, 1992). Frey, however, found no correlation between grain yield and grain protein concentration in some lines from a cross with A. sterilis, which has high-protein genes.

Milling suitability is a different requirement, often in conflict with the grower’s needs, although they may not be aware or informed of this. Larger grains, like those of Belar (Guerin, 1965), a low yielding oat, are favoured by millers. So is Cooba (Mengersen, 1963), which is a high yielder in southern areas, but a lower yielder in the northern, rust and frost liable areas of NSW. The fact that millers pay more for certain varieties may sway the farmer into growing low yielding or unadaptable varieties. The registered seed grower of such varieties, even if they are better informed, are unlikely to advise against the variety they are selling if it is unsuited to the farmers' needs. Farmers thus get locked into growing a variety often for a small temporary cash advantage, ignoring potential long-term profits for the farm, where value is added to the grain in terms of wool, lambs and beef.

Testing of high-vigour varieties

Testing environments

Trials were conducted at several locations in NSW representing 6 different climates and environments. Northern NSW (i.e. the summer rainfall zone) was further sub-divided into 5 climatic zones, from Glen Innes in the east to Tamworth, Gunnedah, Curlewis, Narrabri in the west. A sixth climatic zone, located in Leeton, NSW (uniform rainfall zone), at elevation at 152m and latitude 34° 33” S., was also used as a trial site. Leeton is an irrigated region in the southern rainfall area of the Riverina of NSW.

Methods used

Grains harvested from the trials were assessed for hectolitre weight (i.e. weight per 1000 grains) and for groat percentage. About 40 distinct oat varieties and selections were assessed for grain quality over a 5 year period.

Trial results

Testing in 6 different climatic zones demonstrated that 1000-grain weight and groat percentage were varietal characteristics. There were, however, separate components of quality which develop independently, depending on the location of the crop grown, and the season.

Glen Innes, at an elevation of 1,128m and latitude 29° 42” S. on the New England Tablelands, proved to be the ideal climate for developing high groat percentage and large grain size.

Table 5.1 shows that Garry, Acacia and VRAF.VRSF No. 23 excel in hectolitre weight, but of these VRAF.VRSF No. 23, a parent of the High-vigour cross, 28 x 23, has the highest groat percentage.

Table 5.2, in giving the mean 1000 grain weights of Bundy and Belar, shows an increasing environmental stress (reduction of hectolitre weight) from east to west across the state, that is, from the Tablelands to the Western Plains of NSW. An exception to this trend was where the High-vigour cross produced their highest groat percentage at Narrabri in 1961, the warmest site and season of all those contrasted. These values were 75.8% for P4315 (cultivar inventory number 38), 75.0% for P4314 (cultivar inventory number 39) and 74.2% for P4316 (cultivar inventory number 46). Under these conditions they also exceeded Cooba in hectolitre weight.

Table 5.3 shows the results of grain quality tests on the High-vigour lines in F₇ generation over 3 sites. In making the F₄ directed bulk, Blackbutt, from an F₃ bulk, there is a tendency to produce a higher weight grain within this High-vigour cross (Cross A). Within Cross C, however, the reverse trend is shown, which is not surprising as 0614 x B, G5, has an even larger grain than Orient (Palestine x Dawn), the largest grained Australian oat variety and very susceptible to grazing and frost damage.

A range of seeds from both the High-vigour cross as well as conventionally bred varieties, are presented in Figure 5.1, 5.2 and 5.3.

Recommnedations for extension

For greater efficiency in the breeding and recommendation of oat varieties to farmers, northern NSW (within the summer rainfall zone) can be divided into at least 5 distinct sub-zones between 29°S and 32°S latitude. The central division (32°S to 34°S latitude) of uniform rainfall has 5 sub-zones, as is the case with the southern division (34°S latitude to the Victorian border). In the case of wheat breeding, rainfall isohyets are used for varietal recommendations. In the case of oats, a winter crop in Australia with greater vernalisation requirements than wheat, which is a purely grain crop, isohyets of the length of the frost-free period (Commonwealth Bureau of Meteorology, 1965) correlate more closely with oat yields and quality.

Table 5.1 Grain quality, as groat (gt %), of Australian cultivars and accession lines.

^a New England Tablelands, NSW; ^b Murrumbidgee Irrigation Area, NSW; ^c Liverpool Plains, NSW. Trials were conducted during 1959; ^d later reselected in 1961 as P4319 for extensive yield testing and released to farmers as Blackbutt in 1974; kg/hl = kg/hectolitre (weight in kilograms per unit volume); Wt = weight of 1000 seeds (groat + hull) in grams.

Table 5.2 Oat grain quality, as weight in grams of 1000 seeds (groat + hull) and as groat %, of cultivars at four sites in Northern NSW^a.

^a wt = weight of 1000 seeds (groat + hull) in grams. gt% = groat percentage, ^b 1961, ^c 1963, ^d averages of seed weight of 2 cultivars common to all sites and years. Grain finishing stress increases from east to west, from moist to dry climates.

Table 5.3 Grain quality of mainly High-vigour oats (Cross C and Cross A, 28 x 23), F₇ generation testing.

^a grams/1000 seeds; ^b groat percentage. Tests made at the NSW Department of Agriculture, Agricultural Research Station, Glen Innes. Note large grain size of 871 family and of 0614 x B, F₂. Grain samples were from yield trials conducted at Tamworth, Gunnedah and Narrabri in 1963.

Figure 5.1 Grain shape and sizes of the parents of the High-vigour cross.

Figure 5.2 Grain shape and sizes of the High-vigour varieties and lines (Blackbutt, Carbeen and P4315) alongside conventionally bred cultivars.

The NSW Department of Agriculture High-vigour selections have been proven in some cases to combine grain quality per se with milling and dual-purpose characteristics. These findings indicate the potential of these lines for current oat breeding programs in the winter rainfall areas and in summer rainfall countries on the eastern sides of continents, like China and the eastern sides of North and South America.

Conclusions

The results presented in this chapter suggest that northern NSW could be divided into 5 climatic regions, from east to west, for the purpose of recommending oat varieties. Glen Innes, at an elevation of 1,128m and latitude 29° 42" S on the New England Tablelands, proved to be the ideal climate for developing high groat percentage and large grain size. A sixth climatic zone, located in Leeton, NSW, at elevation at 152m and latitude 34° 33" S., was the second most favourable centre, but required irrigation for full grain development.

At least three oat breeding and testing centres are needed for NSW: Glen Innes, Tamworth and Temora. Frost and grazing resistant oat varieties are greatly needed to implement sound rotation of crops, early fallowing to kill wild oats (Avena fatua), rather than heavy reliance on herbicides, which are bringing out resistances in this weedy species, and early sowings of oats in February and March to prevent erosion and allow flexibility in the management of livestock.

The grain quality tests reported in this chapter may become increasingly significant particularly in the light of the relatively recent discoveries of the effects of oats on human and animal health and the indispensable role of oat bran, formerly not so highly regarded.

References

Commonwealth Bureau of Meteorology. 1965. The Climate and Meteorology of Australia, Bulletin No. 1.

Frey, K.J. 1992. Setting and achieving oat breeding goals to meet specialised and new end uses. 4^th International Oat Conference, Adelaide.

Guerin, P.M. 1965. Bundy – The breeder’s report: A new mid-season oat variety for northern NSW. Agricultural Gazette NSW 76: 667-669.

Mengersen, F. 1963. Choosing oats for grazing and grain in Southern NSW. Agricultural Gazette NSW 12, 678-683.