Sub clover root diseases 1 What we did

Sub clover root diseases 1. What we did a) The issue: - 29 M ha of sub clover pastures affected by root disease - Complex of 4+ pathogens particularly impacting autumn-winter gap b) What we did: - Practical flexible chemical & cultural options for producers to manage root diseases across autumn-winter feed gap - Understanding of factors influencing expression of root disease - Predicta B tests that are applicable for sub clover pastures

2. What we found (outputs to date) 1. Environment drives epidemics (temp, soil moisture, soil type, nutrition) 2. First DNA soil test probe for Aphanomyces established 3. Rhizobium inoculation (increase nodulation but no effect on disease) 4. Avoid continuous heavy grazing (decrease root disease, increase nodulation and plant size) 5. Greater % clover (less grass) (reduce root disease across pathogens) 6. Seed fungicides (Increase germination and survival by up to 30%) 7. Complete fertilizer (increase shoot productivity by up to 1. 5 fold) 8. Fungicide sprays (reduce disease up to 30%; spectacular field examples) 9. First Aphanomyces resistance [Dalkeith, Riverina, York (Antas, Leura)] 10. Cultivation (reduce root disease & increase productivity up to 75% or more) 11. Disease-resistant/tolerant cultivars (increase productivity by 4 -5 fold)

3. Key farmer messages to date 1. Maintaining high clover content reduces disease 2. Reseeding using fungicides improves establishment 3. Improving nutrition increases productivity of diseased clover 4. Fungicide sprays can sometimes be spectacular 5. Cultivation increases productivity for years 6. FUTURE: Long term: disease-resistant/tolerant cultivars

4. Economic on-farm benefits Chemical & cultural treatments have potential to give flexibility in managing soil-borne diseases over autumn-winter feed gap period On-farm benefits: Up to 23% increase in subclover productivity are achievable

5. Unanswered questions (opportunities) FUTURE: Long term critical need for cultivars with both ‘field tolerance’ + ‘resistance’ to soil-borne pathogens (yet missing) Why now need to find and develop resistant/tolerant cultivars • Formal resistance screening ceased in 1999 • No resistance screening in current pre-breeding & breeding projects (except RIRDC) • Resistances of recently released cultivars largely unknown (‘duty of care’) • Sub clover breeding/selection is ‘blind’ from disease resistance perspective • See naturally selected tolerant/resistant clover ecotypes across Australia • No search for disease tolerance (except Phytophthora races, AWI project)

Screen in presence of total pathogen complex (+ races) identifies both disease ‘field-tolerance’ and disease ‘resistance’ A 4 -5 FOLD INCREASE IN AUTUMN-WINTER PASTURE PRODUCTIVITY IN SEVERELY DISEASED PASTURES IS OBTAINABLE