Bacillus thuringiensis cry1Ab gene confers resistance to potato againstHelicoverpa armigera (Hubner)

Summary Helicoverpa armigera is one of the important insect pests adversely affecting the yield of potatoes in India. A synthetic gene encoding the insecticidal crystal protein (Cry1Ab) ofBacillus thuringiensis (Bt) has been introduced into five genotypes of potato usingAgrobacterium tumefaciens. Southern analysis of DNA from transgenic plants confirmed the integration and copy number of the transgene. Double-antibody quantitative sandwich ELISA analysis demonstrated high levels of Cry1Ab protein expression in transgenic plants. Insect bioassays on the leaves of transgenic plants showed considerable protection against the larvae ofH. armigera in terms of leaf area consumed and larval weight reduction.     

Marker-assisted Breeding for Disease Resistance in Potato

Sub-project 5 of BIOEXPLOIT aims to design durable disease resistance through marker-assisted breeding by converting existing markers for high-throughput application, developing and validating high-throughput marker technologies and pyramiding major R genes and/or quantitative trait loci into elite material. Activities include (1) the fine mapping of the quantitative trait locus PiXspg which accounts for a large proportion of the variation in late blight resistance, (2) converting SNP-based markers and an AFLP marker to easy-to-use-markers, (3) testing of progenies with combined sources of late blight resistance for presence of R genes and agronomic features, (4) backcrossing new sources of resistance to S. tuberosum and molecular screening of breeding materials with marker GP94 linked with gene Rpi-phu1 conferring late blight resistance, (5) evaluating potato clones with enhanced resistance against Phytophthora infestans under field conditions of Toluca (México), and (6) developing populations and marker-assisted breeding for disease resistance.     

Variability in the response toPseudomonas solanacearum of transgenic lines of potato carrying a cecropin gene analogue

Summary Transgenic potato plants of cv. Désirée carrying an antibacterial gene, coding for a cecropin lytic peptide analogue, were inoculated with a virulent strain ofPseudomonas solanacearum under controlled conditions. The disease index scored during three repeated infection trials indicated an increased variability in plant response among the transgenic lines which gave either a more susceptible or a more resistant response to the pathogen when compared with untransformed Désirée. Immunity toP. solanacearum was not observed, but it was possible to select a group of transgenic lines that showed resistance levels and disease development curves comparable to the field resistant cv. Cruza 148.     

转Cry1Ab-Ma基因玉米CM8101对亚洲玉米螟抗性研究

利用q RT-PCR和ELISA等方法测定转Cry1Ab-Ma基因玉米CM8101不同世代、不同组织目标基因表达量,开展玉米螟室内和田间生测鉴定,评价转Cry1Ab-Ma基因玉米CM8101对亚洲玉米螟的抗性。结果表明,Cry1Ab-Ma基因在CM8101各组织中均有表达,不同世代间目的基因的表达量无显著性差异,遗传稳定。室内生测结果表明,转基因玉米CM8101各组织均对亚洲玉米螟具有显著的杀虫效果,不同世代间玉米螟的存活率均无显著性差异。田间接虫鉴定结果表明,CM8101在T3、T4、T5世代的抗性等级均为1级,抗性水平为高抗。     

转Cry1A.401基因抗虫玉米CM8302和CM8303对亚洲玉米螟的抗性研究

采用农杆菌介导法获得转Cry1A.401基因抗虫玉米CM8302和CM8303,通过多代回交与自交获得BC₄F₁、BC₄F₂和BC₄F₃世代的转基因玉米材料。利用qRT-PCR和ELISA方法明确转基因抗虫玉米叶片、花丝和子粒均有Cry1A.401基因表达,不同世代间目的基因表达量无显著差异。田间接虫鉴定结果表明,CM8302和CM8303三个世代心叶期和吐丝期的抗性等级均为1级,抗性水平为高抗。室内生测结果表明,亚洲玉米螟幼虫取食CM8302心叶、花丝和子粒第6天存活率分别为0、4.0%和4.0%;取食CM8303心叶、花丝和子粒第6天存活率分别为0、4.0%和2.0%。分析显示转基因抗虫玉米CM8302和CM8303的心叶、花丝和子粒均具有显著杀虫效果且遗传稳定。     

Resistance to <Emphasis Type="Italic">Potato virus Y</Emphasis> in a Multitrait Potato Breeding Scheme without Direct Selection in Each Generation

In an experimental breeding scheme to improve late blight (Phytophthora infestans) and white potato cyst nematode (Globodera pallida) resistance of tetraploid potato over three generations of crossing and selection, 15 clones survived the final selection, and these were derived from 15 great-grandparents. There was no direct selection for resistance to Potato virus Y (PVY), but 14 out of the 15 great-grandparents were resistant to PVY and three had extreme resistance. Thirteen of the 15 descendants had PVY resistance and one extreme resistance. This was within the range expected for a random (unselected) sample from the genotypes of the great-grandparents. Hence, we found no evidence for any positive or negative association between PVY resistance and the attributes selected. The conclusion is that laborious selection is not required in every generation when many parents have PVY resistance, including some with more than one copy of a PVY resistance gene or resistance at more than one locus. However, in the future, determining the major virus resistance genes present in potential parents in each generation using diagnostic molecular markers would prevent susceptible × susceptible crosses being made and maximise the number of resistant × resistant ones.