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ARET, Annual Report 2001, p. 54-5.

Nematode resistance screening programme in fire and sun-air cured tobacco

ANON.
ARET, Agricultural Research and Extension Trust, Lilongwe, Malawi
Meloidogyne javanica is the most common root knot nematode in Malawi. Yield losses from nematodes infestation when in combination with soil borne diseases are usually heavy. Five South African introductions: NOD 8, NOD 12, NOD 31, NOD 90 and OD 697 were crossed with MW 86-57 in the glasshouse during the 2000/01 season at Kandiya. Malawi Western and MW 86-57 were the fire-cured controls while NOD 12 and NOD 31 were used as the nematode resistant checks. Seed was sown in nematode infested soil in small pots. "S" mixture was applied at sowing using cup number 5. After six weeks, 4 lines from the reciprocal crosses with scores of less than 2.0 together with M. Western were transplanted into two big pots with sterilised soil. No fertilisation was done at or after transplanting to avoid affecting nematode populations. Immediately after supplying, potted seedlings were inoculated with nematodes around the root zone of each plant. At flowering, healthy plants were selfed. At harvesting, each selfed plant was uprooted to check. root galls. Plants with nematode scores of less than 2.0 in a scale of 0 to 10 were selected for further screening in the field. 0 denoted no root galling and 10 meant all plants selected had root galls. None of the breeding lines tested under nematode pressure showed any resistance. One of the resistant checks under test, NOD 31 also did not show any signs of resistance. It exhibited only 25% resistance. NOD 12 another resistant check had shown 80% resistance. The fire and sun-air cured controls: MW 86-57 and M. Western succumbed to nematodes. A number of them died before the last score was taken. Screening was to be repeated in the glasshouse in winter as the performance of the test materials was not satisfactory.