Determination of genetic variation is important to the plant breeders for development of high yielding variety. The aim of the current study was to investigate the genetic diversity of nine tamarind cultivars, out of nine four flowering cultivars using random amplified polymorphic DNA (RAPD) markers. Ten Random amplified polymorphic DNA (RAPD) primers were used to assess the genetic diversity in four flowering cultivars and five non-flowering of tamarind trees. The average genetic similarity level among the four flowering cultivars and five non-flowering accessions grouped into six clusters groups at 0.76%. RAPD profiles of all the tamarind were compared and a total of 58 scorable bands were produced with seven primers ranging from one for OPG-13 to twelve for OPA-R15. Genotypes which were morphological closely related were found to be unrelated at the molecular level. A sizeable amount of intrapopulation diversity recorded in the present study which can be utilized in hybridization programmes to efficiently introgress the desirable trait of interest.
A study on the seasonal variations in the population structure of Haemonchus contortus and Trichostronglyus colubriformis was conducted for a period of 12 months in a typical large scale sheep farm on improved pasture in Peninsular Malaysia which has a wet tropical climate. Successive groups of helminth-free tracer lambs were grazed for 4 weeks together with naturally infected sheep and were necropised for worm counts 2 weeks after their removal from the pasture. The monthly populations of H. contortus fluctuated slightly except in May and August during which more worms were found in the tracer animals. The numbers of T. colubriformis were comparatively high from October to December 1992 and again in March 1993, low during April and June 1992. Small numbers of hypobiotic larvae of H. contortus were detected in the tracer animals. Development and survival of infective larvae of H. contortus and T. colubriformis on pasture were investigated by spreading faeces containing eggs on grass plots in October 1993, February and May 1994. Development of the eggs to the infective larvae occurred within one week and their survival times were 7 weeks in the 3 experiments. The potential for control by rotational grazing is discussed.
The host–parasite relationships of several notoedrid and teinocoptid mites of two Malaysian bats, Cheiromeles torquatus (the hairless bat) and Cynopterus brachyotis (the common fruit bat), were studied.C. torquatus is parasitized by five species of Notoedres (family Sarcoptidae)—N. alexfaini, N. longisetosus, N. elongatus, N. rajamanickami and N. cheiromeles. Two, N. alexfaini and N. longisetosus, are responsible for generalized mange, which affects mainly the trunk. The three remaining species produce small, discrete lesions, each having a distinctive morphology and polarity.Notoedres elongatus causes papilliform swellings, usually over the bony parts of the wing. It inhabits deep burrows in the swellings, which consist largely of hyper-plastic connective tissue heavily infiltrated with round cells. The lesions produced by N. rajamanickami resemble those of N. elongatus, except that they are located on the head in the neighbourhood of the vibrissae and are not elevated. N. cheiromeles dwells in cupules in the stratum corneum on various parts of the body, including the wings. These cupules are formed as a result of an intense hyper-keratosis in the immediate vicinity of the mites.The reaction of the skin of Cynopterus brachyotis to the teinocoptid mite, Teino-coptes asiaticus (family Teinocoptidae), expresses itself chiefly as an extensive acanthosis. There is little or no thickening of the stratum corneum except on the lips of the epidermal cupule in which the anterior end of the mite rests. The dermis underlying the mite undergoes moderate fibroblastic proliferation.We would like to thank Mr Lim Boo Liat of the Institute for Medical Research, Kuala Lumpur, and Mr Eric Alfred of the National Museum, Singapore, who very kindly allowed us to examine material from their collections. Mr Lim also assisted in other ways and proved to be a genial and helpful host when we visited his laboratory at the IMR. We are also most grateful to Professor John Harrison, who so generously provided us with space in his department.
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