The lesion nematode, Pratylenchus goodeyi, has been found to be a major problem of ensete (Ensete ventricosum) in Ethiopia, and is also recorded on banana and in association with the bacterial wilt disease caused by Xanthomonas campestris pv. musacearum. The implications of this bacterial/nematode complex are potentially serious for both crops, but especially for ensete, which is a starch staple for about 7 million people in Southern Ethiopia.

Experimental and commercial results are given of work on bacterial wilt (Pseudomonas solanacearum (E. F. Smith) E. F. Smith) in tomato. The use of resistant cultivars and a grafting technique was investigated. Resistant cultivars from Malaysia, Philippines and the USA were tested but no satisfactory results were obtained. The simple grafting technique overcame the disease in the hot wet climate of Brunei. The best stock donor found was Solarium torvum, while best quality fruits consistent with good yields were given by the Roma variety. The grafting method is now being recommended to farmers in the hope that Brunei can become self-sufficient in a commodity which at present is wholly imported.

No abstract

1. The desirability of employing the genetic variation present in diploid and tetraploid wild species for the improvement of the cultivated hexaploid species stimulated an investigation into the synthesis of various amphiploid forms in Avena.2. Five amphiploids at the hexaploid level have been produced, but the present investigation is limited to the amphiploids developed from the cross A. barbata (2n = 28)×.A. strigosa subsp. hirtula (2n= 14), their hybrids with the natural hexaploid species and with other amphiploid types.3. These amphiploids, like their parents, possessed black paleae, with hairs and a fairly strong geniculate awn on both the lower and upper grains. The bases of both the lower and upper grains possessed the articulation surfaces characteristic of A. fatua. Their hybrids with A. fatua were similar in spikelet morphology, but the A. sterilis type of spikelet was dominant in both the amphiploid 6x × A. sterilis and amphiploid 6x × A. byzantina. Partial dominance of the cultivated type base over the shedding type was evident in crosses with A. sativa and A. nuda but the naked caryopsis and multiflorous spikelet were recessive in the latter cross. In crosses between the A. barbata/A. hirtula 6x amphiploid and the A. abyssinica/A. strigosa 6x amphiploid (Cc 4387) the hybrid exhibited a reversal of dominance relationships, with the cultivated base type of Cc4387 being completely recessive to the shedding base.

No abstract