Present status of genetics of rust resistance in flax

Summary Present knowledge of host genes conferring resistance to rust in flax and their genetics are reviewed. There are at least 34 genes conferring resistance to rust occurring in seven groups, namely, K, L, M, N, P, D and Q. Expression of these host genes is affected by temperature, genetic background and by the inhibitor gene present in certain rust strains. Recombination analysis indicates that genes within each of the M and N groups are probably closely linked and that of the L group are genetically complex. When testcross progeny between two genes of the L group were screened, susceptible and modified recombinants were recovered. Some of these susceptible recombinants yielded rare resistant revertants in their progeny. Mechanism of such reversion is not defined but appears to follow a definite pattern. It is also indicated that some of the recombinants represent new specificity. A molecular approach of cloning host genes in flax is described.     

Male-sterility in the grain amaranth (Amaranthus hypochondriacus ex-Nepal) variety Jumla

Summary Twenty naturally occurring male-sterile plants were recovered from a normal population of the grain amaranth, variety Jumla. The identification of the male-sterile plants is possible during anthesis and after flowering. The male-sterility in this variety is conditioned by a single recessive nuclear gene ms.This research was supported by Grant No. AMA-KE-4-83-22 (CRG GRANT) from the National Academy of Science, USA. Reprint requests to V.K. Gupta.     

The inheritance of flowering time in garden stock (Matthiola incana R.Br.)

Summary The inheritance of flowering time (FT) in a cross between early-flowering (P1) and late-flowering (P2) Matthiola incana genotypes, was investigated. The distribution of FT in F1, F2 and BC1 generations indicated an additive genetic control with partial dominance of earlines alleles, particularly with regard to double-flowered plants. Single-flowered plants flowered earlier than double-flowered plants, averaged within both parental lines; however, the mean difference between singles and doubles was 16 days for P1 as compared with 6 days for P2. This flower-doubleness related delay in FT was found to be heritable, by analysis of F3 family means. The implications of these results on the breeding of stock cultivars is discussed.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1138-E, 1993 series.     

棉花黄萎病抗性的分子研究进展

本文综述了棉花黄萎病菌的分子鉴定，棉花黄萎病抗性的遗传基础，分子标记在棉花抗黄萎病方面的应用，棉花黄萎病抗性基因的克隆及转化等方面的研究进展。     

Noise and Interference in Two Way CATV

The funneling effect of noise is the main difficulty in two way CATV modification works. This paper discusses the source of noise and interference, the mechanism to form noise funneling, the regularities of distribution, the characteristics of the spectrum, etc. The purpose is to find the way of reducing funnel noise. The invading noise has the greatest effect on the upstream of two way CATV system, which mainly comes from the indoor of the users. The increase of the number of cable modem will not obviously make greater funneling noise. The cable connectors are the main source of producing and invading noise in outdoor cable network, which is a threat to the safty of the whole upstream channel.     

Genetic control of fertility in the oil palm (Elaeis guineensis Jacq.)

Summary A study was conducted on the segregating populations from tenera × tenera, tenera x fertile Pisifera crosses and tenera selfings. Pisifera palms were categorised as (1) fertile Pisifera palms if producing mature ripe bunches regularly under natural conditions, and (2) partially female sterile pisifera palms if producing a few or no bunches in several years.Based on observations on the segregation patterns of the fruit forms (dura, tenera and pisifera) and bunch production patterns, a genetic model was formulated to explain the genetic basis of fertility in the oil palm. Fertility in the oil palm is shown to be controlled by a single gene which is linked to the gene controlling fruit form. Chi-square tests confirmed that the model agreed with the segregating ratios of fruit form and fertility observed.The implications of this finding with regard to oil palm breeding and improvement, and the potential of the fertile pisifera palm for increasing palm oil yields in plantations are discussed.     

Genetics of Resistance in Vicia sativa L. to Orobanche crenata Forsk.

The genetics of resistance of common vetch (Vicia sativa L.) to broomrape (Orobanche crenata Forsk.) was studied for two years by using the P₁, P₂, F₁, BC¹, BC₂, F₂ F₃, and F₄ generations obtained from crosses between resistant and susceptible lines. Resistant lines were selected by screening a world collection m a naturally infested plot. Resistance was tested both under field and greenhouse conditions. The best index to measure resistance was the number of emerged broomrapes per host plant. The results fit the additive-dominance model. The main component of the variation was additivity; dominance and interaction effects seemed to depend on the environment. When dominance is expressed, a low number is dominant over a high number of broomrapes per host plant.     

棉花抗病核不育两用系的培育及应用研究

１９７８ 年开始选用含棉花核雄性不育基因ｍ ｓ１４的两用系４７３Ａ、抗枯萎病品种陕棉９ 号及抗枯黄萎病品种中棉所１２, 通过杂交转育、病圃与非病圃、可育株与不育株的双重交叉选择, 成功地培育出抗枯萎耐黄萎和抗枯萎抗黄萎的核不育两用系抗Ａ１ 和抗Ａ２。并对其抗性遗传、抗性与产量的配合力及其利用情况进行了研究, 以抗Ａ１ 和抗Ａ２ 作母本已选配成３ 个杂交种应用于生产。     

Genetics of parthenocarpy in tomato under a low temperature regime: II Cultivar ‘Severianin’

Summary Genetics of parthenocarpy in cv Severianin was tested under natural low-temperature conditions under which only seedless fruits were produced. Results were consistent with the hypothesis that two recessive genes are involved in the expression of parthenocarpy under low-temperature conditions. One gene, pat-2, has major effects on the expression of parthenocarpy. A second gene, mp, in the homozygous form, influences expression of pat-2 in both the homozygous and heterozygous conformation and may be present in non parthenocarpic phenotypes. Linkage tests, using 26 morphological marker genes, located pat-2 between solanifolia, sf (chromosome 3 site 111) and baby-lea syndrome, bls (chromosome 3 L site 74) close to sf. The location of the minor gene for parthenocarpy, mp, was not detected.     

High genetic diversity of Fusarium circinatum associated with the first outbreak of pitch canker on Pinus patula in South Africa

The disease known as pitch canker results from infection of Pinus species by the fungus Fusarium circinatum. This fungus also causes a serious root disease of Pinus seedlings and cuttings in forestry nurseries. Pinus radiata and P. patula are especially susceptible to the pathogen, but there are no records of pitch canker on P. patula in established plantations. To date, only planting material of this tree species in nurseries or in plantations at the time of establishment have been infected by F. circinatum. Symptoms of pitch canker have recently emerged in an established P. patula plantation in South Africa and this study sought to determine whether the symptoms were caused by F. circinatum. Isolates from cankers were identified as F. circinatum using morphology and DNA-based diagnostic markers. Microsatellite markers were then used to determine the genetic diversity of a collection of 52 isolates. The entire population included 17 genotypes representing 30 alleles, with a greater number of genotypes collected from younger (three- to six-year-old) than older (12- to 19-year-old) trees. Both mating types of F. circinatum were present, but no evidence of sexual recombination was inferred from population genetic analyses. This is the first record globally of pitch canker on P. patula trees in managed plantations. It is of significant concern to South Africa, where P. patula is the most important Pinus species utilised for plantation forestry.