Physiological Response and Resistance of Plants to Disease and Pest Stress

This paper outlines the physiological responses of plants to pathogenic microbial infection and pest feeding stress,as well as the resistance characteristics of plants to diseases and pests,and proposes new directions for future research on crop resistance to diseases and pests.The objective of this paper is to provide a reference framework for the breeding of crops with enhanced resistance to diseases and pests,the utilization of natural immunity in crops,and the efficient prevention and control of diseases and pests.This framework is intended to facilitate the healthy and sustainable development of the agricultural industry.

Development of Marker-Free Transgenic Cry1Ab Rice with Lepidopteran Pest Resistance by Agrobacterium Mixture-Mediated Co-transformation

CrylAb gene was transformed into four rice varieties, Zhejing 22, Zhejing 27, Jiahua 1 and Xiushui 63 mediated by Agrobacterium-mixture co-transformation. Rice genotype had an important effect on callus induction and transformation efficiency. Different mixtures of Agrobacterium strains （EHA105 and EHA101） contained Hpt and CrylAb genes resulted in different frequencies of resistant calli. There was no correlation between the frequency of transformants with the ratio of the Agrobacterium strain mixture contained Hpt and CrylAb genes. A total of 509 transgenic plants were obtained from the four rice varieties, and 272 T2 progenies were analyzed for CrylAb and Hpt genes. PCR analysis revealed that 412 regenerated plants were Hpt positive （80.94%）, 62 plants were also CrylAb co-transformants （15.05% in total frequency）, and 42 plants among the 272 T2 progenies were CrylAb positive but Hpt negative. This suggests that marker-free transgenic plants could be produced by co-transformation mediated by mixed Agrobacterium strains with the selectable marker gene and target gene Southern blot analysis of five independent marker-free T2 transgenic lines co-transformed from Zhejing 22 showed that CrylAb gene had been inserted into rice genome with a single copy. The transgenic plants showed significantly stronger resistance to lepidopteron than the non-transgenic plants under no application of insecticides against lepidopteron.

Plant Resistance to Pest and Research Progress of Its Genetic Improvement

Pest damage is a significant factor that cuts agricultural production, and cultivation of pest-resistant varieties is the most economic and effective approach of controlling pest damage. Plant pest resistance includes antixenosis, antibiosis, and tolerance. Current popular methods for the genetic improvement of crop pest resistance are traditional breeding method, transgenic breeding, and molecular mark-assisted breeding. This paper introduced major mechanisms and genetic bases of plant pest resistance, ＂and reviewed research progress of domestic and international genetic improvement of plant pest resistance, analyzed the problems and its de- velopment prospects.

Resequencing-based QTL mapping for yield and resistance traits reveals great potential of Oryza longistaminata in rice breeding

As a natural genetic reservoir, wild rice contains many favorable alleles and mutations conferring high yield and resistance to biotic and abiotic stresses. However, there are few reports describing favorable genes or QTL from the AA genome wild rice O. longistaminata, which is characterized by tall and robust habit and long tassels and anthers and shows high potential for use in cultivated rice improvement. We constructed a stable BC_(2)F_(20) backcross inbred line(BIL) population of 152 lines from the cross of 9311 × O.longistaminat. Some BILs showed large panicles, large seeds, and strong resistance to rice false smut, bacterial leaf blight, rice blast spot, and brown planthopper. Genomic resequencing showed that the 152 BILs covered about 99.6% of the O. longistaminata genome. QTL mapping with 2432 bin markers revealed 13QTL associated with seven yield traits and eight with resistance to brown planthopper and to four diseases. Of these QTL, 12 for grain yield and 11 for pest and disease resistance are novel in Oryza species.A large-panicle NIL1880 line containing QTL qPB8.1 showed a nearly 50% increase in spikelet number and27.5% in grain yield compared to the recurrent parent 9311. These findings support the potential value of O. longistaminata for cultivated rice improvement.

Risk of control failure to insecticides malathion,profenophos+cypermethrin mixture,and fipronil in boll weevil(Coleoptera:Curculionidae)populations from Bahia,Brazil

Background To control the boll weevil Anthonomus grandis grandis(Coleoptera:Curculionidae),a key pest of cotton in the Americas,insecticides have been intensively used to manage their populations,increasing selection pressure for resistant populations.Thus,this study aimed to detect insecticide resistance and assess insecticide control failure likelihood of boll weevil populations exposed to malathion,profenophos+cypermethrin,and fipronil insecticides.Results Twelve populations of the boll weevil were collected from commercial cotton fileds of the state of Bahia,northeastern Brazil.These populations were exposed to malathion,profenophos+cypermethrin mixture,and fipronil,at their respective maximum label dose for field applications.Three replicates of 10 adult beetles were exposed to the insecticides and mortality was recorded after 24 h treatment.The control failure likelihood was determined after 48 h.Highest median lethal times(LT_(50))were observed for malathion and the profenophos+cypermethrin mixture.Resistance to at least one insecticide was detected in 11 populations;three populations were resistant to malathion and profenophos+cypermethrin;seven were resistant to all insecticides tested.The resistance levels were low(<10-fold)for the three insecticides.Among 12 populations tested,58%of them exhibited significant risk of control failure for the insecticides malathion and profenophos+cypermethrin.The insecticide fipronil was efficient for the control of the boll weevil in 83%of the populations.Conclusions The results confirm the significant risk of insecticide control failure in the boll weevil populations to the main compounds used in the region.Thus,proper insecticide resistance management plans are necessary for the boll weevil in the region,particularly for malathion and profenophos+cypermethrin insecticides.

Increasing Accumulation Level of Foreign Protein in Transgenic Plants Through Protein Targeting

Targeting of the synthesized polypeptide in the cells is an important research field in modern cell biology. Cowpea trypsin inhibitor (cpti) gene has been modified and a fusion protein gene (sck) was produced by fusing a signal peptide sequence at cpti 5' end and an endoplasm reticulum (ER) retention signal peptide at cpti3' end respectively. The signal peptide can direct the newly synthesized polypeptide into ER, while ER retention signal can make the protein retained in the ER and its derivative protein body. ELISA test indicated that the accumulation level of foreign CpTI protein in sck transgenic tobacco (Nicotiana tabacum L.) was two times higher than cpti transgenic tobaccos and some individuals were four times higher. At the same time, sck transgenic tobacco has a high resistance to Lepidoptera pest due to the increased accumulation level of foreign CpTI protein. The strategy of foreign protein targeting can be used to increase the accumulation level of foreign protein in transgenic plants and can be widely applied to other related research field in plant genetic engineering.

Relationship between trophic component of different poplar strains and occurrence of Saperda poplnea

An experimental area of poplar was established in Songyuan of Jilin Province in 1999 for testing the resistance of different poplar stains to Saperda poplnea. Incidence of S. poplnea on ten poplar strains were investigated, and the main trophic component of branches of these poplar trees were measured and analyzed in April 2001. The results showed that there existed significant difference in population size of S. poplnea on different poplar strains, and the branches of these poplar strains have significant difference in nutrient component and content of amino acids. The population size of this pest had a significantly positive correlation with dissolvable total sugar and water content but had no significant correlation with content of total nitrogen and protein nitrogen.

Comparison of three transgenic Bt rice lines for insecticidal protein expression and resistance against a target pest, Chilo suppressalis （Lepidoptera： Crambidae）

Two transgenic rice lines （T2A-1 and T1C-19b） expressing cry2A and crylC genes, respectively, were developed in China, targeting lepidopteran pests including Chilo suppressalis （Walker） （Lepidoptera： Crambidae）. The seasonal expression of Cry proteins in different tissues of the rice lines and their resistance to C. suppressalis were assessed in comparison to a Bt rice line expressing a crylAb/Ac fusion gene, Huahui 1, which has been granted a biosafety certificate. In general, levels of Cry proteins were T2A- 1 〉 Huahui I 〉 T1C-19b among rice lines, and leaf 〉 stern 〉 root among rice tissues. The expression patterns of Cry protein in the rice line plants were similar： higher level at early stages than at later stages with an exception that high Cry 1C level in T 1 C- 19b stems at the maturing stage. The bioassay results revealed that the three transgenic rice lines exhibited significantly high resistance against C. suppressalis larvae throughout the rice growing season. According to Cry protein levels in rice tissues, the raw and corrected mortalities of C. suppressalis caused by each Bt rice line were the highest in the seedling and declined through the j ointing stage with an exception for T1 C-19b providing an excellent performance at the maturing stage. By comparison, T1C-19b exhibited more stable and greater resistance to C. suppressalis larvae than T2A-1, being close to Huahui 1. The results suggest crylC is an ideal Bt gene for plant transformation for lepidopteran pest control, and T1C-19b is a promising Bt rice line for commercial use for tolerating lepidopteran rice pests.

Mapping of a New Gene Wbph6(t) Resistant to the Whitebacked Planthopper, Sogatella furcifera, in Rice

A rice population consisting of 90 TN1/Guiyigu F3 lines was employed to analyze the linkage between DNA markers and a new gene Wbph6(t) conferring resistance to whitebacked planthopper, Sogatella furcifera By using the mapping approach of bulked extremes and recessive class, Wbph6(t) was mapped onto the short arm of chromosome 11 with a genetic distance of 21.2 cM to SSLP marker RM167.

An SI integrated pest management model with pesticide resistance to susceptible pests

In this paper,epidemnic diseases among pests are assumed to occur,so pests are divided into susceptible pests and infected pests,and only susceptible pests are harmful to crops.Considering spraying pesticides and releasing of natural enermies and infected pests to control pests,as well as the long-term application of the same pesticide to induce resistance,an integrated pest management with pesticide resistance is established.The pollution emission model is introduced to model the action process of pesticides,which well reflects its residual and delay effects.By using comparison theorem of impulsive differential equation and analysis method,the threshold condition for eradication of susceptible pests is obtained.Then we analyze the frequency of spraying pesticide on the success of pests control.It shows that it is not that the more frequently pesticides are applied,the better the result of the susceptible pests control is.From the sensitivity analysis,the key factors on the threshold are obtained.Finally,the strategies to control susceptible pests are given,including switching pesticides and releasing infected pests and natural enemies elastically.

Enhanced Resistance of Snowdrop Lectin （Galanthus nivalis L. agglutinin） Expressing Maize to Asian Corn Borer （Ostriniafurnacalis Guenée）

In order to enhance the resistance to pests, transgenic maize (Zea mays L.) plants from elite inbred lines containing the gene encoding snowdrop lectin (Galanthus nivalis L. agglutinin; GNA) under control of a phloem-specific promoter were generated through the Agrobacterium tumefaciens-mediated also studied. Thirty-six independently derived plants were subjected to molecular analyses. The level of GNA expression at 0.13%-0.28% of total soluble protein was observed in different transgenic plants. The progeny of three GNA-expressing independent transformants that were derived separately from the elite inbred lines DH4866, DH9942, and 8902, were selected for examination of resistance to ACB. These plants synthesized GNA at levels above 0.24% total soluble protein and enhanced resistance to ACB was demonstrated by exposing the plants to insects under greenhouse conditions. Semi-artificial diet bioassays also showed the toxic effect of GNA on ACB. Field evaluation of the transgenic plants supported the results from the artificial trial. In the present study, we have obtained new insect-resistant maize material for further breeding work and have found that GNA-expressing plants not only gained significant resistance to homopterans, but also showed toxicity to ACB, which is a type of Lepidoptera.