Linkage of downy mildew resistance genes Pd 1 and Pd 2from Allium roylei Stearn in progeny of its interspecific hybrid with onion (A. cepa L.)

Summary Male meiosis of the interspecific hybrid between Allium roylei and A. cepa is undisturbed relative to its parents. Based on meiotic data, A. roylei is concluded to be a closer relative of A. cepa than A. fistulosum. Segregation ratios for downy mildew resistance among BC₁ and F₂ progenies from the F₁ between A. roylei and A. cepa indicate the presence of two dominantly inherited, weakly linked nuclear resistance genes, Pd ₁ and Pd ₂, in A. roylei (recombination frequency 0.32±0.03). Presumably Pd ₁ and Pd ₂are the first genes described in Allium residing in one linkage group. The prospects of exploiting A. roylei in onion breeding seem very promising.     

Location-Specific and Across-Location Selections for Seed Yield in Populations of Common Bean, Phaseolus vulgaris L.

Two populations of common bean, Phaseolus vulgaris L., were used to make three independent location-specific selections at Palmira, Quilichao, and Popayán, Colombia. Also, three across-location selections were made by alternating generations between Palmira and Popayan, between Quilichao and Popayán, and among Palmira, Quilichao, and Popayán. The seven highest yielding lines selected from each environment and population along with 14 parents and two checks were evaluated for seed yield, seed weight, maturity, and reaction to an-thracnose, angular leaf spot, and common bacterial blight. Mean squares due to evaluation and selection environments, selected lines, and their interactions were significant for all traits. Mean yields of selected lines were higher than the mean of parents in both populations. Among location-specific selections, lines yielded higher at their respective selection site. Moreover, selections made at Popayán were higher yielding than those made at Quilichao or Palmira when tested across locations and years. Use of Popayán, a relatively wetter and cooler site, either alone or in combination with other locations resulted in higher yield, higher seed weight, and higher resistance to anthracnose. On the average, location-specific selections were lower yielding than the across-location selections. Among across-location selections, those selected between Palmira and Popayán were the highest yielding in both populations. Selections at Palmira and across all three locations resulted in greater stability.     

Inheritance of resistance to Fusarium wilt in Indian lentil germplasm (Lens culinaris Medik.)

Summary Three lentil genotypes resistant to Fusarium oxysporum f.sp. lentis viz. Pant L 234, JL 446 and LP 286 were crossed with two susceptible ones. The hybrid plants were all resistant in the eight crosses evaluated. Segregation pattern for wilt reaction in F₂, BC(P₁), BC(P₂) and F₃ generations in field and glasshouse conditions indicated that resistance to Fusarium wilt is under the control of two dominant duplicate genes in Pant L 234 and two independent dominant genes with complementary effects in JL 446 and LP 286. A third dominant gene complementary to the dominant genes in JL 446 and LP 286 is present in two susceptible lines. Allelic tests suggest the presence of five independently segregating genes for resistance. Duplicate dominant genes in Pant L 234 are non-allelic to two dominant genes with complementary effects in LP 286 and JL 446 and the third gene complementary to the two genes in JL 446 and LP 286 in susceptible lines JL 641 and L 9–12. Gene symbols among parental genotypes have been designated.     

Natural variation within the genus Beta and its possible use for breeding sugar beet: A review

Summary Sugar beet is a relatively young crop, which supposedly has a narrow genetic base. Natural variation occurring in primitive beet varieties and in wild Beta species has been used for breeding sugar beet. This paper reviews information on desirable characteristics in Beta germplasm and the attempts made for the introgression of such characters into commercial breeding material. After an introduction on the availability of germplasm and the possibilities of hybridisation, attention is focussed on the mating system (especially male sterility), on morphological and physiological characteristics, including yield and sugar content, and on resistances to diseases and pests.     

Transfer of resistance to race 2 of Plasmodiophora brassicae from Brassica napus to cabbage (B. Oleracea spp. Capitata). IV. A resistant 18-chromosome B1 plant and its B2 progenies

Summary The somatic karyotype and meiotic chromosome behavior were studied in an 18-chromosome B₁ plant derived from backcrossing a triploid (Brassica napus x B. oleracea ssp. capitata) F₁ hybrid to cabbage. It is considered that cabbage chromosomes no. 1 and no. 7 were substituted by two shorter B. napus chromosomes. Meiotic disturbances were more apparent during the late stages of second division. Seed fertility of this plant was largely restored in the second backcrosses with both cabbage and broccoli. 18-chromosome B₂ plants resistant to race 2 of Plasmodiophora brassicae were recovered among the progenies.Contribution no. J. 725 from the Research Station, Research Branch, Agriculture Canada, St-Jean, Québec J3B 6Z8.     

Screening for resistance to broomrape (Orobanche cernua) in cultivated sunflower

Racial evolution of sunflower broomrape (Orobanche cernua) has been very rapid in Spain during recent years, in which resistance has been overcome several times and there has been an important increase in areas infested with this parasitic angiosperm. In order to find resistance to a highly virulent population of sunflower broomrape that could be used directly in breeding programmes, three different sets of cultivated plant material composed of 429 entries were tested by artificial inoculation. All evaluated inbred lines from Moden, Canada, were fully susceptible. Out of the 240 P.I. accessions tested, only 10 segregated for resistance to broomrape, the rest being susceptible. From the 160 USDA breeding lines evaluated, 5% were resistant and 19% segregated for resistance to O. cernua. These lines traced back mainly to crosses of RHA 274 and RHA 801 with Russian, Turkish and Romanian hybrids. The origin of P.I. accessions that segregated for resistance were primarily derived from the former USSR and from Romania.     

鸡传染性法氏囊病超强毒901株的分离和鉴定

从暴发鸡传染性法氏囊病死亡率６３．５１％的病死鸡中，分离出一株ＩＢＤ病毒９０１株，经检测，９０１株是一株ＩＢＤＶ超强毒株，可使３１日龄健康雏鸡７１．４％死亡，１０日龄ＳＰＦ鸡胚和３０日龄ＳＰＦ雏鸡１００％死亡。死亡鸡再现了自然暴发ＩＢＤ的典型病变。     

Adaptation of quinoa (Chenopodium quinoa) to Northern European agriculture: studies on developmental pattern

The inheritance of resistance to clubroot, caused by Plasmodiophora brassicae in Brassica oleracea was studied in the F₁, F₂and backcross progenies of three crosses between resistant and susceptible doubled haploid lines. Fresh weights of affected (CW) and healthy (HRW) parts of the root system were measured and R = ln((HRW+0.5)/(CW+0.5)) was used as a measure of resistance. R was shown to have a normally distributed error term with a constant standard deviation over the entire scale. Analysis of means indicated the presence of two complementary resistance genes in one of the crosses. In the other two crosses analysis of means also indicated two-locus interactions, in these cases reducing the cumulative effects of loci homozygous for resistance or for susceptibility alleles. The numbers of segregating resistance genes in these two crosses could not be determined. The presence of epistatic interactions precluded analysis of variance; therefore in this case the measurements were not more informative than the symptom grades analyzed in a previous study.R showed a high rank correlation (-0.85) with symptom grades assigned to the same plants. The results of genetic analyses of R were generally in agreement with those obtained earlier using symptom grades. Symptom grades can therefore be regarded as a reliable measure of symptom development, despite their more subjective nature.     

培养时间和接种密度对咖啡短体线虫繁殖和形态的影响

采用胡萝卜片培养短体线虫技术,测试不同培养时间和接种密度对咖啡短体线虫(Pratylenchus coffeae)繁殖和形态的影响。结果表明,在25℃培养条件下,每片胡萝卜(厚10 mm,直径3 cm)接种25头线虫雌虫,线虫的数量随培养时间的延长而增加,前3周线虫的繁殖系数为6.24,线虫的群体数量增长缓慢;第3~6周线虫的繁殖系数略有增高,为8.99;第6~9周其繁殖系数高达17.88,线虫群体数量快速增长;之后,线虫群体数量增速下降,其繁殖系数降为1.42。在接种不同密度线虫的实验中,线虫的群体数量均显著增长,其繁殖系数在不同接种密度处理中差异不显著;随机挑取10头雄虫与雌虫,比较不同线虫密度对线虫形态特征的影响,结果表明,线虫密度除对雌虫的b值(体长/头顶至食道腺与肠连接处长)有显著影响外,对雄虫和雌虫的其他形态特征测量值均无显著影响。     

Utilization of alien genes to enhance Fusarium head blight resistance in wheat – A review

Fusarium head blight (FHB) is a destructive disease of wheat worldwide. Sources of resistance to FHB are limited in wheat. Search for novel sources of effective resistance to this disease has been an urgent need in wheat breeding. Fusarium head blight resistance has been identified in relatives of wheat. Alien chromatin carrying FHB resistance genes has been incorporated into wheat through chromosome addition, substitution, and translocation. Relatives of wheat demonstrate a great potential to enhance resistance of wheat to FHB.