Resistance to Karnal Bunt (Tilletia indica Mitra) in Synthetic Hexaploid Wheats Derived from Triticum turgidum×T. tauschii

Synthetic hexaploids (SH) developed at the International Maize and Wheat Improvement Center (CIMMYT), involving four Triticum turgidum and nine T. tauschii parents, were evaluated for resistance to Karnal bunt (KB) (Tilletia indica Mitra) during three crop seasons over three years at Ciudad Obregon, Sonora, Mexico. Ten tillers of each SH at boot stage, taken at random, were injected with a suspension of sporidia in water (10,000 spores/ml of water). At maturity the inoculated spikes were threshed individually and evaluated for the percentage KB-infected grains. Based on the mean KB score of each entry for three seasons, 49 % of the SH were immune (0 % infection) to KB. Highly resistant expressions characterized the SH which appeared to be influenced by the resistance of their T. turgidum and/or T. tauschii parents. The overall mean infection of the SH wheats was 0.24 % compared to 56.14 % in the susceptible bread wheat check cultivat ‘WL711’. Transfer of KB resistance genes from SH wheats into bread wheat is currently underway at CIMMYT.     

Short Communication Resistance to common bunt in Hordeum chilense X Triticum spp. Amphiploids

The reaction of tritordeum and its Hordeum chilense and Triticum spp. parents to common bunt incited by Tilletia tritici were determined in field experiments. H. chilense accessions were very resistant, and durum wheats exhibited high to moderate levels of resistance. Conversely, bread wheats were highly susceptible. Resistance from H. chilense was expressed in the amphiploids, although the level of resistance was partially diluted at higher ploidy levels. Hexaploid tritordeums were immune to the disease; some infection was observed among the octo-ploids but at much lower levels than in their respective wheat parents.     

Genetics of resistance to Karnal bunt disease of wheat

Inheritance of resistance to Neovossia indica was studied in a Triticum aestivum line HD 29. To overcome the influence of environment on disease expression, the study was conducted by extensive evaluation of advanced generation (F8) recombinant inbred lines (RILs) developed by single seed descent from the cross WL 711 (susceptible) × HD 29 (resistant. The results suggested that HD 29 possesses three major genes for resistance to isolated Ni7 and two genes for resistance to isolate Ni8. One of the two genes controlling resistance to Ni8 is common with one of the genes conferring resistance to Ni7. These observations have important implications in breeding for Karnal bunt resistance.     

Inheritance of resistance to Karnal bunt (Tilletia indica Mitra) in bread wheat (Triticum aestivum L.)

The mode of inheritance and allelic relationships among genes conferring resistance to Karnal bunt were studied in seven bread-wheat (six resistant and one susceptible) genotypes. The resistant genotypes originated in China (‘Shanghai#8’), Brazil (PF71131), the USA (‘Chris’), and Mexico (‘Amsel’, CMH77.308 and ‘Pigeon’). The susceptible line WL711 was from India. Evaluation of these wheat lines and all possible crosses among their F₁ and F₃ generations (about 100 progenies in each cross) revealed that two partially recessive genes conferred the resistance to Karnal bunt in ‘Pigeon’, whereas four partially dominant genes were present in the other genotypes. ‘Chris’, ‘Amsel’ and PF71131 carry one gene, whereas ‘Shanghai#8’ and CMH77.308 have two genes. ‘Chris’, ‘Amsel’, and PF71131 have different genes, whereas one gene was common to PF71131, CMH77.308 and ‘Shanghai#8’, and another to ‘Chris’ and CMH77.308. Gene symbols were formally designated to the resistant stocks. Resistance was incomplete and stable.     

Resistance sources to Valsa canker (Valsa ceratosperma) in a germplasm collection of diverse Malus species

Although Valsa canker caused by Valsa ceratosperma (Tode ex Fr.) Maire is one of the most destructive diseases in apple ( Malus  ×  domestica Borkh.) especially in eastern Asia, information available to help with breeding against Valsa canker in apples is limited. In this work, 53 accessions of diverse Malus species and their interspecific hybrids were tested for resistance to V. ceratosperma , using an excised shoot assay. Dormant shoots and succulent growing shoots from each accession were inoculated with a virulent isolate AVC-12 of V. ceratosperma , and the length of necrosis was measured at 10 days post-inoculation for the dormant shoots and at 7 days post-inoculation for the growing shoots. The lesion length relative to the susceptible control 'Fuji' in dormant shoots (RL_D) and to that in growing shoots (RL_G) were simple but useful parameters to differentiate between resistant and susceptible accessions. Fourteen accessions from M. baccata , M. florentina , M. halliana , M. micromalus , M. pratii , M. sieboldii , M. yunnanensis , M.  ×  floribunda and M.  ×  platycarpa gave low RL_D and RL_G values of less than 0.6 and were evaluated as resistant regardless of the difference in the stage of growth. The highest level of resistance was found in M. sieboldii . This high level of resistance in M. sieboldii was effective against different isolates of V. ceratosperma .     

Genetic analysis of resistance to Karnal bunt (Tilletia indica,Mitra) in bread wheat

Summary Karnal bunt caused by Tilletia indica in wheat seriously affects the quality of the grains. It is important to generate information on the genetics of resistance to this pathogen so as to aid resistance breeding. For this purpose, four Karnal bunt-resistant lines from China, Brazil and CIMMYT (International Maize and Wheat Improvement Center) and a susceptible Indian cultivar, WL711, were used. The parents, F1 and F3 progenies of five parental diallel crosses revealed that independently segregating loci with three partial dominant resistance alleles were involved in the resistance of Karnal bunt. Lines RC7201/2^*BR2 and Roek//Maya/NAC carried one locus for resistance while Shanghai#7 and Aldan/IAS58 have two and three loci, respectively. One common locus was present in all four resistant parents, which imparted a high level of resistance.     

89份甘肃区试鲜食玉米对丝孢堆黑粉菌的抗性鉴定与评价

为明确不同鲜食玉米品种抗丝黑穗病差异,本研究采用田间人工接种法,于2015—2017年在甘肃省天水市甘谷县对89份甘肃省区试鲜食玉米品种进行抗性鉴定。结果表明,在89份鲜食玉米品种中,9份材料‘彩糯1号’‘、甘甜糯1号’‘、秦粮糯902’‘、九洋双色蜜’‘、AP358’‘、酒糯4103’‘、雅玉1号’、‘禾糯1号’和‘田福糯1号’表现高抗(HR);5份材料‘保糯1号’‘、田福糯2号’‘、甘垦糯2号’‘、金辉306’和‘瑞糯260’表现抗(R);9份材料‘华甜玉6号’‘、白玉909’‘、朝糯606’‘、12009’‘、银玉16号’‘、黄糯90’、‘白甜糯828’‘、原玉糯505’和‘仲甜5号’表现中抗(MR);其余36份和30份表现感(S)和高感(HS);高抗、抗、中抗、感、高感分别占供试玉米品种的10.11%、5.62%、10.11%、40.45%和33.71%。     

The Transfer of Resistance to the Russian Wheat Aphid from Triticum monococcum L. to Common Wheat

Two Triticum monococcum accessions were found to be highly resistant to the Russian wheat aphid. An attempt was made to transfer the resistance to common wheat through direct hybridization or by using bridge species. In each of the four crossing strategies tried, a gradual loss of resistance occurred as hybrids with higher ploidy levels were obtained. It appeared that the level of resistance observed was directly proportional to the ratio of the Triticum monococcum genome relative to other genomes. This would indicate suppression of the resistance gene(s) by the added genomes or dilution of its product(s) by those of homoeoloci. The degree of protection afforded by the gene(s) at the hexaploid level may prove to be small. Plants suspected to be homozygous for the resistance gene(s) were identified; however, further backcrossing to common wheat will be required to improve their agronomic types and meiotic regularities.     

Inheritance of resistance to Tilletia indica (Mitra) in synthetic hexaploid wheat ×Triticum aestivum crosses

Inheritance of resistance to Karnal bunt was investigated in the crosses of four resistant synthetic hexaploid wheats (SH; Triticum turgidum×T. tauschii) and two susceptible T. aestivum cultivars. The resistance was dominant or partly dominant over susceptibility. The SH cultivars Chen/T. tauschii (205) and Chen/T. tauschii (224) have single dominant resistance genes which could be allelic to each other. ‘Altar 84’/T. tauschii (219) appeared to have two dominant genes for resistance. ‘Duergand’T. tauschii (214) possessed two complementary dominant genes for resistance. The work is being extended to involve diverse Karnal bunt-resistant SH and bread wheat cultivars.     

Greenhouse Method for Testing of Resistance of Young Brassica Plants to Alternaria brassicae

Colchicine-induced autotetraploids produced in the medicinally important solanaceous plant Hyoscyamus albus (2n = 68) revealed a general increase in pollen, stomata and seed size, but resulted in the reduction of leaf size and plant height. Also, an initial performance trial showed a decline in biomass yield but an increase in alkaloid content of 16.2 %. Thus, in terms of alkaloid yield, the tetraploids demonstrated a slight improvement over diploids for this economic product. Seed fertility of the raw colchiploids was low but a higher value (> 80 %) could be obtained in advanced generations following rigid selection. High fertility was accompanied by a diploidized meiotic chromosome behaviour in the autotetraploids, with high bivalent pairing and regular anaphase separation. Bivalents were predominantly of open type in the autotetraploids as against a predominance of ring bivalents with distal chiasma localization in the parental diploids. The algebraic estimate of multivalent pairing frequency recorded even in the raw colchiploids was quite low (0.239) compared to that expected on the basis of random pairing (0.667), which further dropped to 0.107 in the C₃ generation. Such reduction in multivalent frequency in autotetraploids could be brought about by a combination of reduction in crossover frequency and correction in pachytene pairing.     

Genetic analysis of resistance to leaf-rust (Puccinia recondita f. sp. tritici) pathotypes in the durum wheats 'PBW 34' and 'DWL 5023'

Genetic analysis of leaf-rust resistance was conducted on two durum wheats. Triticum durum cvs. ‘PBW 34’ and ‘DWL 5023’ were crossed with the leaf-rust-susceptible durum wheat ‘Malvi Local’. The F₁, F₂ and F₃ generations were tested against leaf-rust pathotypes 1, 77A and 108. In ‘PBW 34’, a single dominant gene was effective against each of the pathotypes 1 and 108, whereas two independently inherited dominant genes were effective against pathotype 77A. In ‘DWL 5023’, two independently inherited dominant genes were operative against pathotypes 1 and 77A, whereas a single dominant gene was identified as being operative against pathotype 108. Allelic tests on F₂ generation and joint segregation analysis on F₃ generation seedlings, suggested that two different genes in each cultivar are effective against these three leaf-rust pathotypes. Cultivar ‘PBW 34’ has Lrd1 and Lrd2 genes whereas Lrd1 and Lrd3 genes are present in ‘DWL 5023’.     

Identification of Resistance to Tetranychus turkestani and Analysis of Leaves Surface Wax of Different Cotton Varieties (Lines) in Xinjiang

[Objective] Based on the representative 236 cotton varieties in Xinjiang, the resistance of cotton to mites was identified, and the waxy content and waxy components of leaves were analyzed to lay a foundation for cotton breeding. [Method] In the cotton seedling stage, the waxy content of the leaves of different cotton varieties was determined, and the waxy components of the leaves were analyzed by gas chromatography-mass spectrometry. [Result] Most cotton varieties are sensitive to the damage of cotton mites. There were 2 high resistance varieties, 3 resistant materials, 22 medium resistant materials, 207 sensitive materials and 2 high-sensitivity materials in 236 cotton materials. The waxy content on the surface of cotton leaves was significantly negatively correlated with leaf damage levels. The waxy components of cotton leaves were mainly alkane compounds, containing a small amount of esters, ethers and fatty acids. The content of alkanes and esters in waxy leaves of high-resistance cotton germplasm materials was higher than that of high-sensitivity materials. The compound with the largest difference in content are C₂₄H₅₀, C₃₅H₇₂ and C₁₇H₃₆. [Conclusion] These results lay a foundation for further study on the effects of waxy content on host selection and mite resistance of cotton mites.     

对中国南方部分籼型杂交水稻纹枯病抗性的评价

由立枯丝核菌引起的水稻纹枯病是世界性的水稻严重病害之一,且在育种和生产上可利用的抗病种质极少,迫切需要发掘抗源。本研究鉴定了来自中国南方11个省(市、自治区)的166个籼型杂交稻组合对纹枯病菌的苗期抗性。未发现免疫或高抗的组合,但不同组合间的抗性差异极显著,平均病情指数符合正态分布N(5.27,0.68²),变化幅度为2.84~7.64。根据动态聚类分析,参试组合被划分为抗、中抗、中感、感和高感5级,分别占总数的1.20%、13.86%、36.14%、43.37%和5.42%。参试的大多数组合为感病,仅K优88和中优9801抗病,但其抗性还需在大田进行成株期验证。用Bayes法建立了各抗性级的判别函数,判别准确率达96.39%。根据综合病情指数,上述5级的组合分别占总数的1.20%、13.25%、63.25%、21.69%和0.60%。与动态聚类比较,两者极显著相关(r＝0.81,P<0.01),说明这两种方法均可用于水稻对纹枯病的抗性评价。但动态聚类法较适用于接种环境相对一致的苗期鉴定,而不能比较不同环境条件下的鉴定结果;综合病情指数法则不受时间、地点和批次的限制,更具实用性。通过这两种方法共筛选出26个抗或中抗的组合,它们之间的遗传距离为0.04~0.71;在遗传距离为0.36处,可将其中的22个组合聚为一簇,表明其遗传基础较窄。系谱追踪表明26个抗或中抗的杂交稻亲本亲缘关系较近。因此,在抗纹枯病育种中,需要拓宽抗病种质的遗传基础,培育聚合有数量抗性的材料或组合。     

CryIA(a)-pta双价抗虫基因转化粳稻及二化螟抗性评估

向作物中转多价抗虫基因是增强作物抗虫性、拓宽抗虫谱、延长抗虫时限的有效措施。从粳稻品种吉粳81、吉粳88和通887的成熟胚诱导出愈伤组织,以愈伤组织作为转化的受体,利用农杆菌介导法,转化苏云金杆菌毒蛋白基因CryIA(a)和半夏凝集素(Pinelliaternataagglutinin,PTA)基因。表达双价抗虫基因的载体p3300-bt-pta的bt和pta分别由Ubiquitin启动子和CaMV35S启动子驱动,宿主菌株为EHA105。用除草剂草丁膦(PPT)筛选得到转基因植株25株。以bt基因和pta基因两端序列为引物在一个反应体系同时做2个基因的PCR检测,检测到bt、pta基因的2条带,Bar基因的PCR检测也显阳性。转化株对PPT除草剂抗性鉴定呈抗性,证明外源基因已整合到水稻基因组中。水稻二化螟接虫鉴定结果表明,23株转基因植株抗虫性比对照明显提高,2株表现感虫。     

甘薯黑斑病抗性鉴定中薯块接种的抽样方法

采用二级抽样方案设计和相应的统计分析方法，研究甘薯黑斑病抗性鉴定的薯块抽样方法，以提高鉴定方法的准确性和稳定性。试验结果表明应选择中等大小均匀的薯块５－７块，每个薯块上接种１０个病斑，在其它接种条件控制不变的情况下，可以得到较小的误差。     

普通野生稻的抗水稻白叶枯病(Xanthomonas oryzae pv. oryzae)新基因Xa-23（t）的鉴定和分子标记定位

经抗谱评价、 抗性类型比较、 遣传分析鉴定出一个来自普通野生稻的抗白叶枯病新基因Xa-23（t）(暂名)。 结果表明它是迄今已知基因中抗谱最广, 抗性导入效应很强的一个完全显性的全生育期抗性基因。 用携有新基因Xa-23（t）的一对近等基因系(JG306／／Xa-23（t）)构建F2群体中选出160个单株用SSR(微卫星)标记进行基因定位     

Genetic Analysis of Resistance to Xanthomonas campestris pv. oryzae (Ishiyama) Dye in a Rice Breeding Line ARC 10464

The genetics of resistance to three Indian pathotypes of Xanthomonas campestris pv. oryzae, namely, IX01, IX08 and IX09, was studied in a landrace of Indica rice ‘ARC 10464’. Resistance to each of the two pathotypes IX01 and IX09 was governed by two independently-inherited dominant genes while a single dominant gene was operative against patho-type 1X08. The joint segregation tests conducted on F₂ plant progenies (F₃ families) using pathotypes IX01, IX08 and IX09 suggested that the gene/(s) effective against each of the pathotypes are different.     

小白菜抗黄曲条跳甲种质资源的抗虫性鉴定

为了研究小白菜对黄曲条跳甲的抗虫性鉴定方法,采用田间自然鉴定法,参照小菜蛾危害分级标准,比较了黄曲条跳甲成虫为害48个品种小白菜的叶面积损失百分率。结果表明,现行的小菜蛾危害分级标准不适用于黄曲条跳甲成虫;进一步分析发现48个品种小白菜叶片的叶面积损失百分率与其叶片孔洞数显著正相关(r=0.354),表明计数叶片受害孔洞数可以用来鉴定小白菜对黄曲条跳甲成虫的抗虫性。为了创新小白菜对黄曲条跳甲的抗虫性种质资源,采用"叶片受害孔洞计数法"筛选了100个品种小白菜对黄曲条跳甲成虫的抗虫性,得到了5个相对抗虫品种(‘新矮青-9’、‘新夏春3号’、‘918’、‘泰国种子-2’、‘夏冠’)和5个相对感虫品种(‘楚青325-6’、‘青优’、‘鸡毛菜’、‘12#耐抽苔青梗×668-1’、‘富士’),5个相对抗虫品种孔洞数间均无差异,但均极显著低于5个相对感虫品种,这些材料为小白菜抗虫育种奠定了基础。     

Screening of Tomato Somaclones for Resistance to Bacterial Canker (Clavibacter michiganensis subsp. michiganensis)

To facilitate testing large numbers of tomato soma-clones for resistance to bacterial canker, a fast screening procedure was developed. Two inoculation methods were investigated, i.e. excision with an infected scalpel of I) one cotyledon of 2-week-old seedlings, and II) the first true leaf of 3-week-old seedlings, followed by applying a drop of inoculum on the wound. Inoculation by method II discriminated well between populations of partially resistant and susceptible tomato genotypes. A criterion for the selection of single, putatively resistant plants, based on rating scores of the severity of wilting symptoms, was proposed and tested with plants of a Lycopersicon peruvianum accession with a relatively high level of resistance to bacterial canker. Progenies of 279 somaclones, derived from tissue explants of the susceptible tomato cultivar ‘Moneymaker’, were evaluated for resistance. The presence of somaclonal variation for morphological characters in these populations was previously shown. However, no differences were detected between the somaclone population and controls in either mean susceptibility or distribution of plants over disease severity categories. Moreover, plants with major increases in resistance were not detected. These results suggest that the potential of somaclonal variation as a source of resistance to bacterial canker may be limited.