Mechanism of rice variety resistance to the yellow stem borer,Scirpophaga incertulas (Walker)

Yellow stem borer(YSB),Scir-pophaga incertulas(Walker)has be-come the main rice insect pest onceagain along the Changjiang Riversince 1990s.Unfortunately,no ricevariety with resistance to YSB hasbeen reported so far.Japonica Zhen-dao 2 with moderate resistance toYSB was found.In 10 rice vari-eties with different resistance levels,YSB individuals showed distinct de-velopmental rates,and the asyn-chronous development even occurredin the same rice variety.In this

Study on the Relationship Betweenthe Toxin of Phytophthora infestans(Mont.) de Bary and Resistance of Potato

Plant pathogenic fungi produce mycotoxins which may lead host plants to produce disease symptoms and may have a significant positive role in the course of disease development.The putative Phytophthora infestans toxins were prepared by culturing in liquid medium（60 g rye and 10% tomato juice L-1） for 1 mon at 17℃,filtering through four layers of cheesecloth and being precipitated by ammonium sulfate.The resulted putative toxin solutions were used to study the effects on 3 potato varieties（both leaf and tuber tissues）.The results show that potato leaves and tubers exhibit symptoms similar to the late blight resulted from P.infestans infection.Potato varieties reacting differentially to both the toxin dilutions and toxins produced by different P.infestans isolates suggested the presence of toxin-mediated specificities between potato and P.infestans.Potato leaf and tuber tissues have different and contrary reactions to the toxin.Toxin-mediated specificities are likely present between potato and P.infestans.

Accumulation Characteristics and Resistance to Heavy Metal Contamination of Agaricus bisporus Varieties in Shanxi Province,China

In order to evaluate the accumulation characteristics of heavy metals in the cultivars of Agaricus bisporus in Shanxi Province and to select the varieties with high resistances to heavy metal pollution, atomic absorption spectrophotometer and the atomic fluorescence spectrophotometer were used as the determination methods to compare the heavy metal contents and accumulation characteristics of 6 different varieties. The results showed that 3 heavy metal elements （lead, chromium and cadmium） were tested in the 6 varieties of A. bisporus , all of which were contaminated by heavy metals, but basically no beyond the national standards for food safety. In general, these varieties had less quality risk and could be eaten safely. The accumulation characteristics of heavy metals in these varieties were analyzed, and the varieties were screened according to the resistance to heavy metals pollution. The results showed that variety No. 1 and No. 6 were the varieties with strong comprehensive resistance to the 3 types of heavy metal pollution, and variety No. 3 was a species with weak comprehensive ability in resisting heavy metal pollution.

New technique for identifying varieties resistance to rice blast

After 8 yrs lab experiments and field tests, an advanced technique for identifying varieties resistance to rice blast was developed by a research group in Plant Protection Institute, Zhejiang Academy of Agricultural Sciences. With this technique, the inoculum was prepared on a maize-rice-straw-agar media which was suitable for sporulation of most rice blast pathogen isolates. To avoid possible virulence variation during the vegetative growth, the conidia were harvested and preserved for later different sets of resistance evaluation tests. A simple and precise new method—smear inoculation was used for infection. The experi-

Evaluation and screening for resistance of some varieties(lines)to major diseases and insect pests of rice

During 1984-1988,2,231 varieties(lines)from International Rice Testing Program(IRTP)were evaluated and screened for resistance to riceblast(Bl),bacterial blight(BB),sheath blight

Bacterial Community in Different Populations of Rice Brown Planthopper Nilaparvata lugens(Stl)

The structures of bacterial communities in the brown planthopper （BPH） Nilaparvata lugens （St^l） from different geographic and resistant virulent populations were analyzed by using denatured gradient gel electrophoresis （DGGE）. Results showed that the bacterial communities in BPH nymph from the first to the fifth instars varied with nymphal growth and development. The bacterial communities in the first-instar BPH nymph were similar to those in adults. Nine geographic BPH populations were divided into three groups based on the cluster analysis of DGGE fingerprint. The first group was from the Philippines; the second group was from Thailand and Hainan, Yunnan and Zhejiang provinces of China; and the third group was from Vietnam and Guangxi, Hunan and Jiangxi provinces of China. BPH populations adapted to different resistant rice varieties. The BPH populations from Mudgo （with resistant gene Bphl） and ASD7 （with resistant gene bph2） differed with those of the susceptible rice variety TNI.

Study on the Accumulation of Heavy Metals in Varieties of Agaricus bisporus

The accumulation characteristics and resistance to heavy metal pollution of six varieties of Agar/cus b/spoms were studied. The results showed that arsenic, mercury and cadmium content could be detected in the six varieties, and all of the varieties were contaminated by heavy metals ,but they did not exceed the limits in the national standards for food safety. These varieties had a low quality risk and can be eaten safely. Varie-ties 1 and 6 were strongly resistant to the three kinds of heavy metals, while variety 4 was weakly resistant to heavy metal pollution.

Breeding of Maintainer Line and Sterile Line Brown Planthopper Resistant Rice Using Marker-assisted Selection

Guangxi common wild rice variety brown planthopper highly resistant introgression line HS204 was taken as antigen donor material,hybridization,backcrossing,and molecular marker-assisted selection methods were adopted,to select maintainer line and sterile line materials,so as to provide excellent material foundation for resistance breeding of hybrid rice. Through the marker-assisted selection,it obtained 4 pieces of homozygous resistance gene maintainer line intermediate materials( 100B,101B,102B and 103B),and 2 pieces of resistant sterile line materials( 100A and 103A). All 10 combinations that have testcross with highly resistant sterile 100A showed higher level of brown planthopper resistance: 100A/R2586,100A/KR838,and 100A/KR527 had high resistance level,the others had low to intermediate resistance;100A/KR527,100A/R2586,100A/Minghui 63,100A/Fuhui 838 and 100A/Gui 99 combinations had yield per plant significantly higher than the control group( Teyou 7118),increasing by 14. 45%-49. 26%. The obtained resistant lines are expected to provide a better gene source for the breeding of resistant sterile lines of hybrid rice and the obtained resistant sterile lines can be directly used in the selection of three-line hybrid rice.

Maize and the maize weevil:advances and innovations in postharvest control of the pest

The review focused on recent advances and innovations on the use of maize varietal resistance and plant materials in the control of Sitophilus zeamais Motschulsky.New biological techniques for assessing the resistance of varieties of maize to postharvest infestation by S.zeamias were highlighted.It was suggested that routine analysis of plant species is particularly important to cope with the problem of resistance to synthetic insecticides in weevil control.So the paper also revealed the important technical guidelines and scoring system for testing plant materials for insecticidal activity.Effective postharvest insect pest management strategy should form part of the overall crop husbandry for preserving the quality of the produce.Use of resistant varieties is the best approach to overcoming the problems of synthetic insecticides in weevil control.However,breeding maize crop to improve resistance against the maize weevil is associated with some technical limitations.These limitations include lack of inter-specific cross-compatibility,methodological constraints,biotic variation,undesirable genetic linkages,and limited knowledge of genetic bases of resistance.During screening of plant species for insecticidal activities,an untreated control and a reference insecticide whose efficacy in different agro-ecological zones is known should be designated and the plant material should be tested at economically justified doses.The review presented some advances and innovations on the use of maize resistance(including new formulae and scoring systems)in the control of weevil infestation and addressed maize quality and safety after pest-control process.Findings will enhance reorientation of research focus and provide new impetus for the protection of stored maize against S.zeamais attack.