Dr. Stephen Allen, CSD plant pathologist, discusses this seasons disease rankings.

Steve Allen has just completed this year’s round of disease ranking trials. Before we go into some of the details of that Steve, you might make a comment about what is the disease ranking system that we use.

The disease ranking systems have been developed to get away from arbitary descripters like good, fair or poor resistance. The idea is to come up with a quantitative ranking system which would rank varieties and give a relative position in terms of how resistant they were or how susceptible they are. So in the case of fusarium resistance ranking we have a standard Sicot 189 and everything is compared to that. If something with a ranking of 200 is twice as good or twice the plant survivors as they do in Sicot 189. In the case of verticillium wilt ranking, the standard is Sicala V-2 and again it comes into the 100, so if something has got a rank above 100 it is better than Sicala V-2, if something is lower than 100 its not as good as Sicala V-2 and again its quantitative.

You have actually just had the FUSCOM meeting and there was some discussion at that meeting about changing the ranking system or whether it in fact did need changing. Have you got any comments as to why people are suggesting that there might need to be some change?

It is reflecting some of the disease pressure in some of the resistance ranking trials. In some of those trials the survival in standard Sicot 189 is a bit less than 5%. We find when you have got such heavy disease pressure that the rankings can be all over the place and I guess that’s the concern. The other concern is in terms of when varieties are close to 100 or between 80 and 120 or under 120 the rankings are consistent across a whole range of disease pressures where, as with the high resistance lines at very high levels of disease pressure you can get some results that fluctuate a bit more but I think, a sub-committee has been formed by FUSCOM and its going to look into that and what ever the result is there will be a system that ranks varieties quite quantatively.

We will find out soon enough but there may be some changes to the ranking system for next season?

I am sure that it will not happen for the next season but in the next few years there could be changes, yes.

This years trial results, could you make some comments about the F-ranks of some of the new Bollgard II® varieties that will be released this season?

The results are looking quite good, we are getting a few numbers now. I should point out in ranking it’s the number in brackets that’s important indicating the number of trials where we have got comparisons and if you look at the Sicot 71 Family which is certainly performing well, the conventional standard has been 108 based on 18 trials. The Sicot 71B is much the same 120, based on 6 trials. The Sicot 71RR, 111 based on 3 trials and the Sicot 71BR stack, 110 on 6. It is fairly consistant across the whole range of conventional and transgenic varieties. With the Sicala 43, it’s the conventional line has a resistance ranking of about 68 which is not very good but the Sicot 43B is up on that close on 80 based on 4 trials and remarkably the Sicot 43BR stack of the Sicala 43 is 128 based on 4 which is significantly better than other members of that family.

If we go to the Sicot 80, the conventional Sicot 80 has had a well established rank of 116 based on 21 trials. The Sicot 80B is very similar 112 based on 4 and it is a bit disappointing that the Roundup® ready version of the Sicot 80 which probably be a dryland consideration maybe it is not such an issue but is 71 based on 3 so certainly the resistance that’s present in the conventional Sicot 80B isn’t present in the Sicot 80RR.

Verticillium is still a major concern to many people, particularly in the mainstream varieties such as the Gwydir and the Namoi and further South. Any comments about how those new varieties might perform in terms of verticillium ranking?

Yes we have got two or three seasons results for the V-ranks, the verticillium ranking and basically in all cases the Bollgard II® or the transgenic versions are as good as the conventionals and that in all cases is round about the level of Sicala V-2. It has been noticed that in actual fact the Bollgard II® and Bollgard II® Roundup Ready® versions are maybe even a bit up on the conventional versions of the various varieties. So that is encouraging.

Steve, the other point would be that we obviously have areas now with very high disease incidence in some parts, particularly in the Darling Downs for Fusarium. Have you got any comments on some of the varietal performance and management of some of the very best variety choices for growers in that situation?

It has been quite remarkable this last year where Sicot F-1 has become available and its got the highest ranking at 209 based on 18 different trials and where farmers have used that and combined that with a later planting, the end of October, there have been some remarkable results and certainly before our field trials on the Downs this year where farmers have identified Fusarium problem fields have gone through with that strategy of a higher ranked variety plus a late planting date they have got incredible results in terms in some cases less than 5% disease in established Fusarium sites which is always hard to believe.

There is obviously a lot of information available to growers and a lot to crunch through. Is there any way growers can find out some of that more detailed information on F-ranks and V-ranks?

Yes, the data has just been made available and its going up on the web now so within the next few days or a week or so it will be fully available on the web. That is one option. We will be talking about it at the winter meetings this next few weeks as we go around the various areas and the Extension Team and myself are only a phone call away.

Further Information: 
Dr Stephen Allen, Robert Eveleigh, John Marshall,  Craig McDonald, David Kelly or James Quinn