Prospects of breeding for blast disease resistance in the oil palm (Elaeis guineensisJacq.)
SummaryBreeding for nursery blast resistance in the oil palm can reduce blast from around 50% to 1–6% loss, when a parent is carrier of dominant resistant gene(s). At such low blast levels, most of the costly agronomic methods to reduce blast incidence, need not be used.Plant material originating from the arid regions in Nigeria is more blast susceptible than that from the rain forest areas.
A comparative study of the cytological and reproductive behaviour of wheat and triticale subjected to two temperature regimes
SummaryA comparison was made of the meiotic stability and reproductive behaviour ofTriticale hexaploide cv. Rosner andT. aestivum cv. Pitic in response to two temperature regimes (15° and 30°C) imposed continuously from premeiosis to maturity. Mean frequencies of MI open bivalents, univalents, and lagging chromosomes at AI were significantly higher in Rosner than in Pitic. Such irregularity would appear to arise from the asynchronous disjunction of chromosomes between Metaphase I and Anaphase I, resulting in meiotic disturbances and a high frequency of abnormal microspores. Despite such abnormalities, floret fertility was equivalent to that observed in Pitic, and the proportion of aneuploids recovered in the progeny, although greater than expected in wheat, was much lower than would be predicted. It is suggested that there is a strong certation effect in the transmission of aneuploid microspores and that the irregularities observed during microsporogenesis do not apply directly to megasporogenesis.No appreciable effect of temperature on meiotic chromosome behaviour during microsporogenesis was observed in either wheat or Triticale. In Triticale, high temperatures (30°C) substantially reduced spikelet fertility, and in contrast, low temperature (15°C) increased the frequency of aneuploids.
Rhizoctonia Solani as a Parasite of Fungi
SUMMARYRhizoctonia solani Kuhn, an important soil-inhabiting parasite of cultivated plants, also parasitizes fungi. Except for Ambylosporium botrytis of the Fungi Imperfecti, only species of Phycom...