21. Not until 1947 was a rust-resistant variety developed at the Central Experimental Farm in Ottawa. 22. Unfortunately, no resistant varieties have yet been found. 23. Resistant varieties accumulate and finally treatment failure occurs.24. Now, it is typical to replace areas that have been infected with resistant varieties of sugarcane. 25. Genetically modified crops engineered to resist herbicides are now more available than conventionally bred resistant varieties . 26. Resistant varieties are available but not commonly used.27. Infection-resistant varieties of the plant are being developed. 28. Fill in the gaps in containers with some of the new, frost-resistant varieties now in local nurseries. 29. The alternative is to plant resistant varieties . 30. In 1993, a National Taro breeding program, with the focus on breeding Taro varieties resistant varieties , commenced.
