Genetics and Mechanism of Resistance to Meloidogyne arenaria in Peanut Germplasm

Segregation of resistance to Meloidogyne arenaria in six BC₅F₂ peanut breeding populations was examined in greenhouse tests. Chi-square analysis indicated that segregation of resistance was consistent with resistance being conditioned by a single gene in three breeding populations (TP259-3, TP262-3, and TP271-2), whereas two resistance genes may be present in the breeding populations TP259-2, TP263-2, and TP268-3. Nematode development in clonally propagated lines of resistant individuals of TP262-3 and TP263-2 was compared to that of the susceptible cultivar Florunner. Juvenile nematodes readily penetrated roots of all peanut genotypes, but rate of development was slower (P = 0.05) in the resistant genotypes than in Florunner. Host cell necrosis indicative of a hypersensitive response was not consistently observed in resistant genotypes of either population. Three RFLP loci linked to resistance at distances of 4.2 to 11.0 centiMorgans were identified. Resistant and susceptible alleles for RFLP loci R2430E and R2545E were quite distinct and are useful for identifying individuals homozygous for resistance in segregating populations.     

Effects of Peanut Genotypes on Meloidogyne Species Interactions

A 3-year microplot study was conducted to characterize the interaction between Meloidogyne arenaria race 1 (MA1) and M. hapla (MH), as affected by the five peanut genotypes: Florigiant, NC 7, NC 6, NC Ac 18416, and NC Ac 18016. The interactive effects on infection (total parasitic forms per root unit) and reproduction potentials of each nematode species and crop damage were determined. As a single population, MA1 had greater infection capacity and caused more crop damage than did MH, but both species had similar reproduction potentials. In mixed infestations, MA1 was more competitive than MH, as reflected by incidence of infection. Infection and reproduction potentials, and crop-damage capabilities of the mixed populations were similar to those of MA1 alone. All peanut genotypes were susceptible to infection by both nematodes. NC 6 was less susceptible to damage by MA1 and the mixed populations than other genotypes. A nematode treatment x genotype interaction was detected for root infection and crop damage, but not for population density or reproduction. With high preplant nematode levels (Pi), the populations reached their peak by midseason, whereas those with low Pi peaked after midseason. Crop damage in the second and third years was correlated with Pi level.     

Antimutagenic Effect of Methanolic Extracts from Peanut Hulls

The antimutagenic effects of methanolic extracts of peanut hulls (MEPH) were evaluated by the Ames test. MEPH inhibited the mutagenicity of 4-nitroquinoline-N-oxide (NQNO), a direct-acting mutagen. MEPH also inhibited the mutagenicity of some indirect-acting mutagens and decreased in the order of 2-amino-3-methylimidazo(4,5-f)quinoline (IQ)>aflatoxin B₁ (AFB₁)>2-amino-6-methyldipyrido(1,2-a : 3′, 2′-d)imidazole (Glu-P-1) > 3-amino-1,4-dimethyl-5H-pyridol(4,3-b)indole (Trp-P-1) > benzo(a)pyrene (B(a)P) for 5. typhimurium TA98, and IQ > Trp-P-1 > Glu-P-1 > AFB₁ > B(a)P for S. typhimurium TA100.     

PCR rescue and analysis of transgene sequences directly from crude extracts of transgenic embryos and plants

We report the application of a PCR-based method in conjunction with automated sequencing for the reliable detection and verification of transgenes in crude extracts of leaf and callus tissue from different plant species. Transformed tissue can be identified easily at any stage of the regeneration process, whether it is via embryogenesis or organogenesis. This allows researchers to focus their attention and resources on truly transformed tissues and avoid unwittingly culturing untransformed tissues. This protocol can also be used to rescue relatively large PCR products as well as duplexing the detection of transgenes. Direct sequencing of the PCR products allows confirmation of the integrity of the transgenein planta.     

HPLC法测定花生根中白藜芦醇的含量

本文采用反相高效液相色谱法测定了花生根中白藜芦醇的含量.选用ODS-C18色谱柱(200 mm×4.6mm,5μm),以甲醇-水(4555)为流动相,流速为0.5 mL/min,紫外检测波长为303nm.结果表明,白藜芦醇峰面积与其浓度之间呈现良好的线性关系,线性回归方程为Y=15879.28X+12350.2,相关系数为0.9996.方法简单,快速,精密度好,回收率为98.8%,相对标准偏差为1.79%.     

Reproduction of Belonolaimus longicaudatus,Meloidogyne javanica,Paratrichodorus minor,and Pratylenchus brachyurus on Pearl Millet (Pennisetum glaucum)

Pearl millet (Pennisetum glaucum) has potential as a grain crop for dryland crop production in the southeastern United States. Whether or not pearl millet will be compatible in rotation with cotton (Gossypium hirsutum), corn (Zea mays), and peanut (Arachis hypogaea) will depend, in part, on its host status for important plant-parasitic nematodes of these crops. The pearl millet hybrid ''TifGrain 102'' is resistant to both Meloidogyne incognita race 3 and M. arenaria race 1; however, its host status for other plant-parasitic nematodes was unknown. In this study, the reproduction of Belonolaimus longicaudatus, Paratrichodorus minor, Pratylenchus brachyurus, and Meloidogyne javanica race 3 on pearl millet (''HGM-100'' and TifGrain 102) was compared relative to cotton, corn, and peanut. Separate greenhouse experiments were conducted for each nematode species. Reproduction of B. longicaudatus was lower on peanut and the two millet hybrids than on cotton and corn. Reproduction of P. minor was lower on peanut and TifGrain 102 than on cotton, corn, and HGM-100. Reproduction of P. brachyurus was lower on both millet hybrids than on cotton, corn, and peanut. Reproduction of M. javanica race 3 was greater on peanut than on the two millet hybrids and corn. Cotton was a nonhost. TifGrain 102 was more resistant than HGM-100 to reproduction of B. longicaudatus, P. minor, and M. javanica. Our results demonstrated that TifGrain 102 was a poor host for B. longicaudatus and P. brachyurus (Rf < 1) and, relative to other crops tested, was less likely to increase densities of P. minor and M. javanica.     

Distribution and Downward Movement of Pasteuria penetrans in Field Soil

Endospores of Pasteuria penetrans were evaluated for their vertical distribution in field soil and their downward movement through soil in the laboratory. In the field trial, the number of endospores attached to second-stage juveniles (J2) of Meloidogyne arenaria race 1 varied greatly in different soil depths. There were higher percentages of J2 with endospores attached in former weed fallow plots during the first 3 years of growing peanut than in former bahiagrass and rhizomal peanut plots (P ≤ 0.05). In weed fallow plots a higher average number of endospores per J2 were maintained in all depths, upper three depths, and upper four depths in 1999, 2000, and 2001, respectively (P ≤ 0.05). However, in 2002, there were no differences in the percentages of J2 with endospores attached and in the average of the numbers of endospores per J2 among the treatments (P > 0.05). In laboratory trials, P. penetrans endospores were observed to move throughout the soil through the percolation of water. After one application of water, some endospores were detected 25 to 37.5 cm deep. Endospores were present at the greatest depth, 37.5 to 50 cm, after the third application of water. These results indicate that rain or water applications by irrigation are likely to move endospores to deeper levels of the soil, but the majority of endospores remain in the upper 0-to-30-cm depth.     

三种花生幼胚蛋白质提取方法比较研究

植物组织(或细胞)的蛋白质提取效率与效果直接影响蛋白质双向凝胶电泳等实验的结果。为探索建立适用于花生幼胚蛋白质(双向凝胶电泳用)提取的最佳条件,尝试了磷酸缓冲液直接提取法、改良的荔枝胚胎蛋白提取法和Trizol(附加)提取法等3种提取方法,根据蛋白提取得率、试剂成本、双向电泳图谱的质量(蛋白质斑点的丰度、分布特点)进行初步评价。结果表明,磷酸缓冲液直接提取法简单但总体效果较差,改良的荔枝胚胎蛋白提取法综合评价最好,与双向凝胶电泳条件更兼容。     

激光辐照花生种子的细胞学效应

本试验考察了用Ar (488 nm)激光辐照对花生种子胚轴细胞形态结构以及根尖细胞染色体的影响。研究结果表明:在辐照功率密度为5.12 W/cm2,时间为10 s、25 s、55 s情况下,胚轴细胞均有不同程度的损伤;且均能诱发根尖细胞染色体畸变。处理时间延长,细胞破坏加剧,主要表现在细胞中膜系统、脂体、蛋白体和细胞核,出现了异形、合并或结构混乱等现象。染色体畸变类型也随之增加。各激光处理剂量均对花生种子萌发产生抑制作用。