An understanding of the attributes required for long-term yield is very important in selecting the right lucerne cultivar. New cultivars have been bred in Australia that possess these attributes. Similarly, the attributes of contemporary North American cultivars now cater better for our needs. The attribute values listed in Table 2.1 indicate that they vary widely between cultivars. The objective in selecting the right lucerne is to match those attributes with the needs of the enterprise involved and the paddock to be sown.
Table 2.1 lists the cultivars available in Queensland in 2001. The cultivars are listed according to winteractivity level and each cultivar is given a rating for winter activity and resistance to the three lucerne aphids, the main root and crown diseases, and leaf diseases. Root disease susceptibility is rated and those with low resistance are only recommended for well-drained soils. From this table, the cultivar can be chosen that best suits the farmer’s needs. If cultivars have similar characteristics, the choice comes down to either local experience or personal preference.
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*This table is a summary of information supplied by seed companies in 2001.
Table 2.1 Characteristics of lucerne cultivars available in Queensland
Notes on Table 2.1
- Key to abbreviations: SAA — spotted alfalfa aphid; BGA — bluegreen aphid; PA — pea aphid;
CCR — Colletotrichum crown rot; PRR — Phytophthora root rot; St E Lep — a leaf damage rating for Stemphylium
and Leptosphaerulina leaf diseases - Pest/Disease ratings: HR — highly resistant, R — resistant, MR — moderate resistance,
LR — low resistance, S — susceptible, N — no information available from seed company.
Cultivars listed in order of increasing winter growth potential from 3 (very slow growth) through 6 (moderate
growth) to 10 (very active growth).
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.Long-term yield of lucerne depends on:
- genetic ability to produce dry matter;
- persistence, which is determined by factors including resistance to diseases and pests, grazing tolerance and management.
All the contemporary commercial cultivars are high yielding, although there is variation in seasonal yield. Highly winter-active cultivars produce about 200/0 of their total annual yield in the winter months, whereas semi-dormant cultivars produce only about 100/o of their total yield in winter. The winter-active cultivars also produce more total dry matter in the first two years after sowing.
The major diseases affecting lucerne yield and persistence in Queensland are caused by fungi. They are: crown rot caused by Colletotrichum trifolii; root rot caused by Phytophthora medicaginis; and the leafspotting diseases caused by Stemphylium vesicarium and Leptosphaerulina trifolii.
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