Plant regeneration from anther culture in Canadian cultivars of flax (Linum usitatissimum L.)

The effect of culture of anthers at 35 °C for one to four days prior to culture at 25 °C in darkness, genotype, anther orientation on callus induction and shoot regeneration in anther culture of flax was investigated. The influence of type and concentrations of cytokinins in the regeneration medium on shoot regeneration was also investigated. The results suggested that culture of anthers at 35 °C prior to continuous culture at 25 °C in darkness did not significantly improve the percentage of anthers producing calli. However, culture of anthers at 35 °C for one day significantly increased the overall efficiency of regeneration compared to no culture temperature treatment. Genotypic effects were significant for the percentage of anthers producing calli and the overall efficiency of regeneration. Anther orientation showed no significant differences. The regeneration medium containing 4.5 μM zeatin had significantly higher percentage of calli forming shoots than the same basal medium containing 0.01 μM TDZ. The importance of these findings for flax breeding was discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of resistance to Fusarium wilt (race 2) in chickpea

The inheritance of resistance to Fusarium wilt (race 2) of chickpea was studied in a set of three crosses, i.e. ‘WR315’בC104’ (resistant × susceptible), ‘WR315’בK850’ (resistant × tolerant) and ‘K850’בGW5/7’ (tolerant × tolerant) in order to investigate the number of genes involved, their complementation and to find out whether resistant segregants are possible in a cross between two tolerant cultivars. Tests of F₁, F₂ and F₃ generations of these crosses under controlled conditions at ICRISAT, Patancheru, India, indicated involvement of three loci (two recessive and one dominant alleles). The homozygous recessive form at the first two loci conferred resistance whereas susceptibility occurred when the first two loci were in the dominant form. A dominant allele at the third locus can complement the dominant alleles at the other two loci to confer tolerance. Occurrence of resistant segregants in a cross between two tolerant cultivars was observed.     

Monogenic resistance in tomato to Fusarium oxysporum f. sp. lycopersici race 3

Summary Resistance to fusarium wilt, incited by Fusarium oxysporum (Schlecht.) f. sp. lycopersici (Sacc.) Snyder & Hansen race 3 in tomato (Lycopersicon esculentum Mill.) was discovered in LA 716, a L. pennellii accession. A resistant BC₁F₃ breeding line, E427, was developed from LA 716. E427 was crossed with the susceptible cv. Suncoast and F₁, BCP₁, BCP₂ (to Fla 7155, a susceptible parent) F₂, F₃, and BCP₂S₁ seeds were obtained. Segregation for resistance following root dip inoculation over three experiments indicated a single dominant gene controlled resistance. Five of the 12 BCP₁S₁'s segregated more susceptible plants, whereas one of the 12 segregated more resistant plants than expected (P<0.05). Three of 23 F₃ lines segregated more susceptible plants than expected while 1 of the 23 had more resistant plants than expected (P<0.05). Segregation in all other lines fit expected ratios. Five of the 23 F₃'s were homozygous resistant which was an acceptable fit to expectations (P=0.1–0.5). The gene symbol I ₃ is proposed for resistance to race 3 of the wilt pathogen. Deviations from expected ratios in data reported here and for other breeding lines indicate an effect of modifier genes and/or incomplete penetrance. Plant age at inoculation and seed dormancy did not affect results.Florida Agricultural Experiment Station Journal Series No. 8101.     

High frequency of plant regeneration from anther culture in flax, Linum usitatissimum L.

The effects of induction medium compositions on flax anther culture were investigated in order to improve the efficiency of callus induction and plant regeneration. Anthers were inoculated onto the modified MS medium supplemented with five different combinations of plant growth regulators. The medium containing the combination of 2mg/l 2,4- dichlorophenoxy-acetic acid (2,4-D) and 1 mg/1 6-benzylaminopurine (BAP) produced a significantly higher number of calli forming shoots/100 responded anthers and a significant increase in overall efficiency of regeneration than the same basal medium containing 1 mg/1 a-naphthalene-acetic acid (NAA) and 2 mg/1 BAP (CK). Among the five levels of thiamin hydrochloride tested, the modified MS medium containing 10 mg/1 thiamin hydrochloride significantly increased the number of calli forming shoots/100 responded anthers and the overall efficiency of regeneration compared with the same basal medium containing 0.1 mg/1 thiamin hydrochloride. Maltose concentration had a significant effect on the percentage of anthers producing call, the number of calli forming shoots/100 responded anthers and the overall efficiency of regeneration. The medium containing 6% or 9% maltose produced the highest overall efficiency of regeneration among the five levels of maltose evaluated. Sucrose concentration significantly affected the number of calli forming shoots/100 responded anthers and the overall efficiency of regeneration, and dramatically affected the frequency of microspore-derived plants and the frequency of spontaneous chromosome doubling in microspore-derived plants. The efficiency of doubled haploid line production obtained in this study appears adequate for applied breeding programmes.     

Comparison of genetic diversity of flax (Linum usitatissimum L.) between Canadian cultivars and a world collection

This study reports results of phenotypic measurements of genetic diversity in the world collection of flax maintained by Plant Gene Resources of Canada (PGRC) and compares the range of diversity in the world collection with the diversity observed in 19 Canadian registered flax cultivars. Morphological and seed‐oil characters were used to describe the phenotypic diversity in 2331 flax accessions. The plants were grown by PGRC at Saskatoon, Saskatchewan, Canada, in 1998 and 1999. The comparison between the Canadian cultivars and the world collection was based on single characters, as well as on character complexes by application of an existing intraspecific classification for the species. Considering single quantitative or qualitative character expressions, the Canadian cultivars represented a wide range in diversity for the species. The variation of characters Canadian plant breeders have selected for (e.g. plant height, seed weight, seed colour, petal colour, oil content) was reduced further than those characters not focused on by plant breeders (e.g. dotting of the sepals, style colour, ciliation of capsule septa, oil quality characters). A comparison of diversity based on the intraspecific classification proposed for flax by Kulpa and Danert, who described 28 botanical varieties, showed that all Canadian cultivars belong to two botanical varieties. This study demonstrates the usefulness of agrobotanical characterization of genebank collections for plant breeding and illustrates the application of the traditional method of intraspecific classification for comparison of gene pools.     

Inheritance of resistance to Oidium liniSkoric in linseed (Linum usitatissimum L.)

Summary Resistance to powdery mildew (Oidium lini) in each of the four linseed cultivars, viz., LC 216, LC 255, LC 256 and LC 269 was found to be conditioned by one dominant gene. Crosses between the resistant parents indicated that the same gene was present in all the cultivars and is designated as Ol.     

PEG介导的棉花枯萎病菌原生质体转化体系的建立

 通过酶解尖孢镰刀菌萎蔫专化型（Fusarium oxysporum f. sp. vasinfectum）FOV1和FOV4菌株幼嫩菌丝的细胞壁产生原生质体,PEG8000介导外源DNA随机插入的方法,分别获得具有抗潮霉素及荧光信号的转化子27个和39个,转化效率（以单位质量的DNA的转化子数计）分别为1350 mg^-1和1950 mg^-1。选取FOV1和FOV4菌株的代表性转化子各3株,经过5代继代培养后,其产孢量、荧光稳定性和致病性均无明显变化。因此,可以认为棉花枯萎菌原生质体的这种转化方法是一种比较稳定高效的遗传转化体系。     

香蕉枯萎病菌4号小种致病力分化的初步研究

自2003年6月至2010年1月,我们通过采集或交流的方式共得到海南、广东、福建、云南和广西等省区的35个市县的56个Fusarium oxysporum f.sp. cubense Race 4菌株,并通过盆栽伤根淋灌法接种巴西蕉苗,系统性地评价了56个Race 4菌株的致病力。实验结果表明：供试的56个Race 4菌株表现出了很明显的致病力分化,其中,强致病力的菌株有29个、中致病力的有9个、弱致病力的有18个,分别占供试菌株的51.79%、16.07%、32.14%。     

胡麻枯萎病生防放线菌的抗菌活性研究

为了筛选对胡麻枯萎病有较好抗性的放线菌,试验对胡麻根围土壤进行了筛选,最终得到1株对胡麻枯萎病病原菌尖孢镰刀菌有较强拮抗作用的放线菌GS2-1.分别测定了它对不同地区分离得到的151株尖孢镰刀菌的抗性,发酵液对孢子和菌丝的抑制作用,研究了其最佳发酵条件,并对发酵液中的抑菌活性物质进行了初步提取和生物活性测定,最后对其在...     

胡麻枯萎病病原尖孢镰刀菌生态生物型的划分研究

通过酯酶同工酶技术将来自中国主要胡麻产区内蒙古、山西、河北、甘肃的17个枯萎病菌株划分4个酯酶型，同时对部分菌株采用人工室内接种同一胡麻材料后的病情进行分析，考察菌株问的致病性。结果表明：同一地区的菌株属于同一酯酶型，同一地区的菌株间的致病性差异不显著，不同地区菌株问的致病性差异显著。     

香蕉枯萎病诱导抗性研究

以防御酶为指标,研究香蕉枯萎病的诱导抗性,以期开发香蕉枯萎病的生防制剂。分别接种串珠镰刀菌、饱和石灰水、无菌水处理组培香蕉苗,7天后接种尖孢镰刀菌,测定过氧化物酶（POD）、超氧化物歧化酶（SOD）、过氧化氢酶（CAT）活性。结果表明：串珠镰刀菌和饱和石灰水对香蕉枯萎病株POD酶有一定影响,但在3~6 min均未达到5%的显著水平;25℃反应15 min,串珠镰刀菌处理SOD的活力（22.967）高于石灰水（18.171）和无菌水（14.322）;2种处理CAT酶的活力曲线略高于对照,但处理间的差异不明显。说明串珠镰刀菌、饱和石灰水能在一定程度上诱导抗性的产生。研究旨在为香蕉枯萎病诱导抗性提供一定的理论依据。     

Apium graveolens PI 181714 is a source of resistance to Fusarium oxysporum f. sp. apii race 4 in celery (A. graveolens var. dulce)

Celery has little genetic diversity and is highly susceptible to the new fungal pathogen Fusarium oxysporum f. sp. apii (Foa) race 4. After screening an Apium graveolens germplasm collection for resistance to Foa race 4, we crossed celery cv. 'Challenger', which is Foa race 2-resistant but Foa race 4-susceptible and A. graveolens PI 181714, which is Foa races 2- and 4-resistant but non-celery type. After selfing F₁s, we screened the F₁S₁ for race 4-resistance and celery-type and then selfed selected F₁S₁. Greenhouse and field trials indicate that three selected F₁S₂ families (76–8-4, 76–8-27 and 76–8-36) are suitable as germplasm for celery breeders for resistance to Foa race 4. A F1S3 76–8–36-124 is either fixed or nearly so for resistance to Foa races 4 and 2. Furthermore, quantitative PCR indicates that PI 181714 is resistant, rather than tolerant, to Foa races 4 and 2, and that this resistance has been introgressed into F1S3 76–8–36-124.     

Inheritance of rust resistance genes and molecular markers in microspore-derived populations of flax

The inheritance patterns of rust resistance genes and molecular markers in microspore‐derived populations of flax were investigated. Plants were produced from anther culture of F₁ plants from two crosses. Microspore‐derived plants in anther culture of flax were identified using molecular markers. Two rust resistance genes and three out of six molecular markers were inherited in expected Mendelian ratios in microspore‐derived populations. Distorted segregation for the other three molecular markers was shown to be the result of over‐representation of genomic fragments from the more responsive parent in the F₁ donor plant. The implication of this study in relation to androgenesis and flax breeding using anther culture is discussed.     

Screening of Kabuli chickpea germplasm for resistance to Fusarium wilt

A total of 1915 Kabuli chickpea lines were screened in a wilt sick plot containing Fusarium oxysporum f.sp. ciceri race 0 at Béja, Tunisia. Complete resistance was found in 110 lines and this result was confirmed by a laboratory screening method. Principal components analysis showed that > 80% of the variation of the resistant lines was explained by hundred seed weight and days to maturity. Cluster analysis divided the resistant lines into four groups: 21 had high seed weight (48.25 ± 3.81 g) and early maturity (95.09 ± 2.50 d), 24 had high seed weight (46.84 ± 2.10 g) and late maturity (117.00 d), 34 had low seed weight (22.35 ± 4.72 g) and early maturity (92.97 ± 3.97 d) and 31 had low seed weight (19.62 ± 5.37 g) and late maturity (112.09 ± 4.51 d). This revised version was published online in July 2006 with corrections to the Cover Date.     

Two genes and linked RAPD markers involved in resistance to Fusarium oxysporum f. sp. Ciceris race 0 in chickpea

The inheritance of resistance to fusarium wilt race 0 of chickpea and linked random amplified polymorphic DNA (RAPD) markers were studied in two F₆:₇ recombinant inbred line (RIL) populations. These RILs were developed from the crosses CA2156 × JG62 (susceptible × resistant) and CA2139 × JG62 (resistant × resistant), and were sown in a field infected with fusarium wilt race 0 in Beja (Tunisia) over 2 years. A1:1 resistant to susceptible ratio was found in the RIL population from the CA2156 × JG62 cross, indicating that a single gene with two alleles controlled resistance. In the second RIL population (CA2139 × JG62) a 3:1 resistant to susceptible ratio indicated that two genes were present and that either gene was sufficient to confer resistance. Linkage analysis showed a RAPD marker, OPJ20600, linked to resistance in both RIL populations, which is present in the resistant parent JG62.     

Screening for resistance in wild Lycopersicon species to Fusarium oxysporum f.sp. lycopersici race 1 and race 2

Wild Lycopersicon accessions were screened for resistance to the Fusarium wilt disease caused by Fusarium oxysporum f.sp. lycopersici (Fol) race 1 and race 2. In total, four isolates of each race were used. Among 17 accessions of six Lycopersicon species tested, a wide genetic variation for wilt resistance was observed. Most accessions were highly susceptible, some showed intermediate resistance, but one accession of L. cheesmanii (G1.1615 = PI 266375) and two accessions of L. chilense (G1.1556 and G1.1558) were highly resistant to Fol races 1 and 2. The resistance in the latter three accessions equalled or was higher than the resistance determined by the known I-genes, that have been widely used in breeding programmes. These newly found resistant accessions provide breeders with more opportunities for Fusarium disease resistance and may contribute to our understanding of Fusarium disease resistance gene organisation and evolution.     

西瓜枯萎病菌遗传分化研究

本试验利用21个RAPD随机引物对50个西瓜枯萎病菌系进行了RAPD扩增,研究了病菌遗传多样性。结果表明,对供试菌系扩增出134条带,其中多态性带113条,占总带数的84.3%。菌系间的遗传相似系数变化在0.45~0.93之间,多数菌系间的同源程度较低。基于RAPD标记聚类分析表明,50个菌系划分为6个RAPD群(RAPDgroups,简称RGs),即RGⅠ,RGⅡ,RGⅢ,RGⅣ,RGⅤ和RGⅥ。其中RGⅠ和RGⅡ各含有一个菌系,分别来自秦皇岛和新疆;RGⅢ和RGⅤ包括2个菌系,分别来自秦皇岛、承德和廊坊、沧州;RGⅣ包括唐山、石家庄、邯郸和新疆菌系;其余的菌系属于RGⅥ。分类结果进一步说明西瓜枯萎病菌间存在着较大的遗传分化。     

不同黄瓜材料对枯萎病的抗性评价

以危害我国黄瓜的优势枯萎病生理小种4为供试菌源,运用室内苗期人工接种和田间成株期病圃检测2种方法对43份黄瓜材料进行了枯萎病的抗性评价,苗期接种筛选出抗病材料7份,中抗材料16份,感病和高感材料20份。其中抗(含中抗)材料占53.5%,感病材料占46.5%。欧洲血缘的抗病(中抗以上)材料占39.5%;华北和日本血缘的抗和中抗材料占13.9%。成株期田间病圃的鉴定结果与苗期接种基本一致,符合率达86.7%。说明苗期接种结果准确,接种方法可靠。同时还表明了黄瓜种质资源中蕴藏着对改良枯萎病抗性有利用价值的基因资源,其中欧洲黄瓜抗源较丰富,华北和日本类型的黄瓜枯萎病抗源相对匮乏。     

棉花枯萎病菌生理小种的分子指纹分析

以我国棉花枯萎菌３个生理小种的２６个代表菌株及国外３ 个不同生理小种菌株进行随机扩增多态性ＤＮＡ（ＲＡＰＤ）分析，共产生了１４０个ＲＡＰＤ分子标记，其中８７８％ 具有多态性。通过聚类分析将供试菌株划分为６个ＲＡＰＤ组，确定了不同小种间的亲缘关系，为确立我国棉花枯萎菌生理小种在国际上的分类地位提供了可靠的分子证据。