Wider ratio' octads (8:0, 0:8, 7:1 and 1:7) regularly occurred in wild-type( +) x white ascospore(w;) crosses of the Pasadena strains of Ascobolus. Control crosses showed that phenocopies and false octad clusters were absent or rare; no reversion from w to + occurred, but mutation from + to to was found at a number of loci, with nearly all 0 + : 8w and many 2 + : 6w octads in + x w crosses arising from mutation, not conversion. Nearly all 8 + : Ow, 7 + : \w and 6 + : 2w octads appeared to arise by conversion.The finding of genuine wider ratio octads implies hybrid-DNA formation at corresponding sites in both pairs of non-sister chromatids in the same bivalent, which conflicts with models of the synaptinemal complex requiring that only two of the four chromatids pair intimately at any point. Octad types arising from hybrid-DNA formation at corresponding sites in both pairs of non-sister chromatids were described and formulae were derived for their frequencies. The lack of genuine wider ratio octads in several other Ascobolus studies was shown to be explicable quantitatively in terms of their conversion frequencies.'Corresponding-site interference' is defined as interference between the two pairs of non-sister chromatids of a bivalent in hybrid-DNA formation at exactly corresponding sites. Formulae based on observed octad frequencies were derived for calculating coincidence values for this kind of interference. Corresponding-site interference was found to be weak, with coincidence values differing between crosses with high and with low conversion frequencies.

Work done byCoconut Research Institute, Sri Lanka, on the genetics and breeding of the coconut palm from 1930 to 1980 is described. It involves studies on: mass selection methods, selection differential, progeny trials, inbreeding depression, estimation of genetic parameters, construction of selection indices and varietal hybridization. Two improved varieties CRIC 60 and CRIC 65 have been produced. An isolated seed garden was established for the large scale production of seed of the improved varieties. INTRODUCTION The Coconut Research Scheme in Sri Lanka was established in 1929, under the Coconut Research Ordinance, No. 29 of 1928. There were three divisions then: technology, genetics and soil chemistry. There was only one scientific officer attached to each division. The genetics division functioned from 1930. Subsequently, the Coconut Research Scheme was upgraded and enlarged into the Coconut Research Institute (CRI) in 1951 with more divisions and scientific staff. The present report covers the work done by CRI on coconut breeding from 1930 to 1980. Those who were in charge of the Division during this period are indicated below. The emphasis on the nature of breeding work varied with the Heads of Division: Pieris concentrated on mass selection, Raghavan on a progeny trial; Liyanage on genetic parameters, controlled pollination and production of improved varieties; Manthriratne on assessment of performance of hybrids.

An analysis of yield data from 31 tea clones grown in replicated trials at four locations revealed the presence of significant genotype-environment interactions. Joint regression analysis showed that a significant proportion of these interactions could be attributed to differences in the linear response of each genotype (clone) to the range of environments. However, estimates of the deviations from regression were also significant, indicating the presence of some unpredictable variation.The response of each individual clone was estimated by computing the regression coefficient of individual yield on environmental mean yield at each location. The clones used in this study had regression values ranging from 0-19 to 2-08, indicating considerable genotypic difference in response to environmental change. Genetic variation in adaptation was also found to be present. Clones of the Assam type were found to possess general adaptation whereas the one clone of Indo-Chinese origin was specifically adapted to low-yielding environments.Some known features of several tea clones are explained on the basis of the linear regression model and a more scientific basis is provided for the recommendations of clones for different districts. The implications of genotype-environment interactions in practical tea breeding and selection are also discussed.

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A total of 39 mutants at the grey-3, grey-4 and grey-5 spore colour loci in Sordaria brevicollis have been investigated for conversion pattern by crossing them with wild type and counting aberrant asci. Twenty-one of the mutants were obtained with ICR170 and all showed postmeiotic segregation only rarely (0-8 % of the aberrant asci); two showed conversion predominantly to wild type (class A) and the other 19 predominantly to mutant (class B). Six mutants were obtained with ethylmethane sulphonate and one with nitrosoguanidine, and they all showed postmeiotic segregation frequently (14-54% of the aberrant asci) and conversion usually about equally frequently in each direction, though with considerable diversity between mutants (class C). Eleven UV-induced mutants comprised one of class B and ten of class C. There was considerable variation in aberrant ascus frequency between alleles, but conversion pattern seemed to be independent of this frequency.