Resistance at the TM-2 locus in the tomato to tomato mosaic virus

Summary There are three known tomato mosaic virus (TMV) resistance factors, Tm-1, Tm-2 and Tm-2 ², in the tomato. Tm-2 ² is currently the most widely utilised in glasshouse cultivars. Both Tm-2 and Tm-2² can induce systemic necroses in response to virus infection. These are considered to be hypersensitive resistance reactions in view of the low virus concentrations in affected plants and because sub-inoculation usually fails to infect all plants possessing the same resistance gene. The literature relating to TMV resistance at the Tm-2 locus in the tomato is reviewed.Virulent strains may readily establish when Tm-1 or Tm-2 are used, but Tm-2 ² confers more effective resistance. The possible development of aggressive isolates capable of affecting Tm-2 ²/Tm-2² plants is discussed. The establishment of virus types which cause systemic necrosis at normal growing temperatures is considered more likely than widespread infection from fully virulent strain 2² mutants. However, the growing of crops isolated from the TMV reservoirs in the soil considerably reduces the likelihood of even this occurring.     

植物病毒检测技术研究进展

介绍了常用植物病毒的检测方法,包括生物学检测法、电镜技术、血清学方法和分子生物学方法中一些较常用的病毒检测方法,同时对各种方法的优缺点进行了比较。     

辣椒单倍体与双单倍体植株叶片光合作用研究

对辣椒单倍体和双单倍体植株的光合作用进行了研究。结果表明 ,在不同光照条件下 ,单倍体植株净光合速率均明显比双单倍体低。在弱光照下 ,气孔的限制作用是单倍体植株净光合速率较低的主要原因 ;而在正常光照下 ,非气孔限制因素是净光合速率降低的主要原因。单倍体植株在强光下受到明显的光抑制 ,单倍体植株净光合速率、气孔导度和表观量子效率均较低 ,在正常光照条件下羧化效率较低 ;光补偿点和细胞间隙CO2 补偿点较高等均是单倍体植株的重要特征     

Resistance to the Barley Yellow Mosaic Virus Complex — Differential Genotypic Reactions and Genetics of BaMMV-Resistance of Barley (Hordeum vulgare L.)

Barley yellow mosaic disease is caused by several viruses, i.e. barley yellow mosaic virus (BaYMV), barley mild mosaic virus (BaMMV) and BaYMV-2. The reaction of different barley germplasms to the barley mosaic viruses was studied in field and greenhouse experiments. The results show a complex situation; some varieties are resistant to all the viruses, while others are resistant to one or two of them only. Crosses between different barley germplasms were earned out in order to test whether genetic diversity of resistance against mosaic viruses does exist, particularly, BaMMV. A total of 45 foreign barley varieties were crossed to German cultivars carrying the resistance gene ym4. In F₂ of 27 crosses, no segregation could be detected, leading to the conclusion that the resistance genes of the foreign parents are allelic with ym4 e.g. Ym1 (‘Mokusekko 3’) and Ym2 (‘Mihori Hadaka 3’). A total of 18 crosses segregated in F₂ indicating that foreign parents, like ‘Chikurin Ibaraki 1’, ‘Iwate Omugi 1’, and “Anson Barley”, carry resistance genes different from the gene of German cultivars, e.g. ‘Asorbia’ or ‘Franka’. By means of statistical evaluation (Chi²-test), the observed segregation ratios were analyzed in order to obtain significant information on the heredity of resistance. All the resistance genes described here as being different from the gene ym4, act recessively. Most of the exotic varieties seem to carry only one resistance gene. In a few cases, more than one gene may be present.     

Transfer of Tomato Leaf Curl Virus Resistance from Lycopersicon hirsutum f. glabratum to L. esculentum

Six lines, i.e., H-2, H-11, H-17, H-23, H-24, and H-36, resistant to Tomato Leaf Curl Virus (TLCV) have been developed with controlled introgression of L. hirsutum f. glabratum into Lycopersicon esculentum. The disease incidence, 120 days after inoculation, of those lines derived from L. hirsutum f. glabratum ranged from 8.3 to 35.0 %, whereas in susceptible varieties it ranged from 95.0 to 100 %. The coefficient of infection (CI) values in the resistant lines were very low, ranging from 0.25 to 4.55, whereas in susceptible varieties CI values ranged from 60.56 to 88.96. Line H-2 had the highest resistance by showing the least disease incidence and CI values. The fruit size and days to maturity in resistant lines were close to those of cultivated susceptible varieties. These lines have the scope for being used as varieties in the TLCV infested areas or as foundation lines for further genetic improvement.     

Major genes for resistance to beet necrotic yellow vein virus (BNYVV) in Beta vulgaris

Summary Inheritance of resistance to beet necrotic yellow vein virus (BNYVV) was studied in segregating F2 and backcross families obtained from crosses between resistant plants of the sugar beet selection Holly-1-4 or the wild beet accession Beta vulgaris subsp. maritima WB42 and susceptible parents. Greenhouse tests were carried out, in which seedlings were grown in a mixture of sand and infested soil. Virus concentrations of BNYVV in the rootlets were estimated by ELISA. To discriminate resistant and susceptible plants, mixtures of normal distributions were fitted to log₁₀ virus concentrations, estimated for segregating F1, F2 and BC populations of both accessions. The hypothesis that Holly-1-4 contained one single dominant major gene was accepted. For WB42, results fitted with the hypotheses that resistance was based on either one (or more) dominant major gene(s) showing distorted segregation, or two complementary dominant genes, which are both required for resistance. Resistance from WB42 appeared to be more effective against BNYVV than resistance from Holly-1-4.This research was carried out as part of a PhD study at the Graduate School Experimental Plant Sciences (EPS), Department of Virology, Wageningen, The Netherlands     

牛病毒性腹泻-粘膜病病毒地方株动物回归试验

【目的】自流产奶牛粪便及血液中分离得到的非细胞病变型牛病毒性腹泻-粘膜病病毒(BVDV),为了解分离毒株的特性,进行回归动物试验;【方法】将此分离毒回归2月龄健康犊牛,接毒25天后扑杀剖检,观察临床症状及病理变化。自犊牛体内采取脾、骨髓、肠淋巴结及血液接种MDBK细胞进行培养,分离病毒,进行细胞传代,将此细胞毒进行RT-PCR检测;【结果】犊牛表现为典型的急性病毒性腹泻症状和病变。自病料分离病毒经MDBK细胞盲传至第9代,均未出现细胞病变。将此细胞毒进行RT-PCR检测,扩增出相应的665bp的片段;【结论】将分离株接种易感犊牛以复制出BVD-MD病症,并从试验牛体内分离得到BVDV,从而进一步确证分离到的毒株属BVDV。     

A molecular marker linked to the Prv1 gene that confers resistance to Papaya ringspot virus-type W in melon

Papaya ringspot virus‐type W (PRSV‐W) is the most prevalent and important viral pathogen of cucurbits in Brazil. It can be effectively controlled by the incorporation of genetic resistance into susceptible melon cultivars. The present study identified amplified fragment length polymorphic (AFLP) markers linked to the PRSV‐W resistance Prv¹ allele. The susceptible yellow‐fleshed melon‐breeding line AF426^prv1 and its nearly isogenic‐resistant line AF426^Prv1, which carries the Prv¹ allele resident in the Indian cantaloupe U.S. Plant Introduction (PI) 180280, were screened for AFLP marker polymorphisms. Of 30 251 AFLP loci, only three were polymorphic between the nearly isogenic lines. Segregation analyses for these three polymorphic markers and the Prv¹ allele using a BC₁ population of 197 plants indicated close linkage (0.5% recombination frequency) between marker EK190 (HindIII‐CGA and MseI‐GTG; 190 bp) and Prv¹. Thus, EK190 might be a useful marker in breeding programmes aiming to develop melon cultivars resistant to PRSV‐W. The other two markers are closely linked to each other, but distantly linked to Prv¹.     

Two chromosome segments confer multiple potyvirus resistance in maize

Potyviruses cause serious yield losses in maize production worldwide. While the maize dwarf mosaic virus (MDMV) predominates in the USA, sugarcane mosaic virus (SCMV) is a major pathogen in China and Germany. In previous studies, inbred FAP1360A revealed complete resistance against both MDMV and SCMV. Two major SCMV resistance genes, Scmv1 and Scmv2, were located on chromosomes 6 and 3, respectively, in populations derived from crosses with the susceptible inbred line F7. For validation of these results obtained in segregating backcross‐ or F_2:3‐populations, near‐isogenic lines to F7 have been produced after one initial cross to FAP1360A by repeated backcrossing to F7, phenotypic selection for SCMV resistance, and marker‐assisted selection for the Scmv1 and Scmv2 regions from FAP1360A. The near‐isogenic line F7R has been studied in detail both at the genomic level and for resistance to different potyviruses. Based on 112 polymorphic simple sequence repeat markers, F7R received genomic segments introgressed from FAP1360A exclusively in the Scmv1 and Scmv2 chromosomal regions. F7R conferred complete resistance to SCMV and MDMV, but also to zea mosaic virus and to systemic infection by wheat streak mosaic virus. FAP1360A, F7, F7R were not systemically infected by high plains virus. Thus, introgression of Scmv1 and Scmv2 from FAP1360A into F7 was sufficient to generate the first potyvirus multiresistant European Flint line reported so far.     

Susceptibility to sharka (Plum pox virus) in Prunus mandshurica×P. armeniaca seedlings

Prunus mandshurica [(Maxim.) Koehne] from Central Asia is a species related to apricot and grown in China and Mongolia. This species has been used in apricot breeding as a source of frost resistance. In addition, P. mandshurica has been suggested as the possible origin of some North American apricot cultivars resistant to sharka (Plum pox virus, PPV). The aim of this work was to transmit the resistance to PPV from P. mandshurica to the Spanish apricot cultivar ‘Currot’ by traditional crossing. The resistance to a Dideron PPV isolate of the descendants of P. mandshuricaבCurrot’ and their progenitors was evaluated under controlled conditions in a greenhouse. The results showed the susceptibility of both, the progenitors and the offspring to PPV, as being much higher than in other apricot seedlings. The results showed that the P. mandshurica accession studied is not a good progenitor in breeding apricot for PPV resistance, but just the opposite. The possible role of P. mandshurica as a source of resistance in apricot resistant cultivars is questioned.