Impact of biocontrol bacteria with Rhizophora mucronata plant parts in suppression of Meloidogyne javanica (treub) chitwood on crop plants

Germination of seeds, shoot length, shoot weight, root length and root weight on okra and mung bean showed promising results when bacterial antagonists viz., Bacillus subtilis, B. thuringiensis, B. cereus and Rhizobium meliloti after multiplication on Rhizophora mucronata plant parts were used at 1% w/w. Complete suppression of root knots was observed on okra and mung bean when R. meliloti and Bacillus subtilis after multiplication on R. mucronata plant parts viz., leaves and stem.     

Evaluation of a Native and Introduced Isolate of Pochonia chlamydosporia against Meloidogyne javanica

Growth chamber and plastic tunnel experiments were conducted to compare the ability of a native and introduced isolate of Pochonia chlamydosporia to colonize the rhizosphere of selected plant species and survive in soil. Effects of the isolates on population density of Meloidogyne javanica and yield of tomato after single or multiple fungal applications were also determined. In growth chamber experiments, both isolates showed a similar ability to colonise the rhizosphere of selected vegetables, except for the introduced isolate, which produced more colony forming units cm^-2 of root surface on tomato and cabbage than the native one. In the tunnel house, both isolates parasitized eggs of M. javanica, and the native but not the introduced isolate increased parasitism after multiple applications. The native isolate was recovered more frequently from soil, and was a better colonizer of tomato roots than the introduced one irrespective of the number of fungal applications. Multiple fungal applications of either isolate reduced the nematode gall rating, and the native isolate also reduced the final egg population in roots. Neither isolates reduced final nematode densities in soil or affected tomato yield when compared to untreated plots.     

Development of Commercially Acceptable Formulations of the Nematophagous FungusVerticillium chlamydosporium

Studies in shaken flasks and a 20-liter bioreactor showed that biomass ofVerticillium chlamydosporiumcould be produced in large quantities in liquid culture. The fungus grew readily in media containing commercially available, low-cost ingredients (e.g., cotton seed meal, soybean meal) and a volumetric productivity of about 0.3 g/h/liter was achieved in the bioreactor. Chlamydospores were not produced in submerged culture, the biomass consisting only of mycelia and conidia. When this biomass was mixed with a carrier (kaolin) and a binder (gum arabic) and the ingredients were granulated and then dried to a moisture content of less than 2%, a biologically active product suitable for application to soil was produced. The fungus grew vigorously from these granules when they were placed on agar and retained its viability when granules were stored in vacuum-sealed bags at 25°C for 12 months. Experiments on tomato in the glasshouse showed that when the formulated product was incorporated into field soil at 10 g granules/liter soil, population densities ofV. chlamydosporiumwere increased to about 10⁴colony-forming units/g soil after 7–14 weeks. Between 37 and 82% of the first generation egg masses produced byMeloidogyne javanicacontained parasitized eggs.     

缺钙诱发大白菜干烧心与细胞壁结构组分变化的关系

缺钙培养诱导大白菜干烧心发生 ,测定心叶组织细胞壁各成分含量的变化。结果表明 ,随着缺钙天数增加 ,果胶、半纤维素 1(HC1)和纤维素的含量呈平稳上升 ,到缺钙处理后第 2 4天时达到高峰 ,随后急剧下降 ,而半纤维素 2 (HC2 )的含量变化不大 ;醛酸在果胶中的含量逐渐呈下降趋势 ,在HC2中的含量先升后降 ,而在HC1和纤维素中的含量变化不大 ;总糖在HC1和纤维素中的含量呈下降趋势 ,在果胶中的含量先升后降 ,而在HC2中的含量变化不大 ;葡聚糖含量也是先升后降 ,在缺钙处理后第 8天有一高峰值 ;尤其是蛋白质在果胶和纤维素部分中的含量较低且变化不大 ,在HC1中的含量极明显减少 ,而在HC2中的含量却极显著增加。同时 ,细胞壁结构发生相应变化。可见 ,大白菜干烧心的发生与细胞壁结构和功能的变化直接相关     

Some Ultrastructural Changes Induced in Resistant and Susceptible Soybean Roots Following Infection by Rotylenchulus reniformis

A developmental electron microscopic study of the parasitism of Rolylenchulus reniforrnis in resistant ''Peking'' and susceptible ''Lee'' soybeans was made during a 21-day period under controlled conditions. Within 2 days of inoculation, the nematode had penetrated the cortical cells to the endodermis where it inserted its stylet, secreted and initiated syncytial formation and cell hypertrophy. Syncytia primarily involved pericycle tissues and, to a lesser extent, xylem parenchyma and endodermis. When identifiable, the cell into which the nematode stylet was inserted to initiate syncytial development was endodermal. Susceptible tissues exhibited two basic phases of development during this infection period: (i) an initial phase represented by partial cell wail lysis and separation; and (ii) an anabolic phase, characterized by organelle proliferation and development accompanied by secondary wall deposits, which provided nutrition for sessile female development. The resistant or hypersensitive reaction (HR) lacked the anabolic phase found in the susceptible reaction, and was characterized by an extension and usually accelerated type of Iysis found in the first phase of the syncytial development. The HR was usually very evident 4 days after inoculation, and could be identified by an almost complete lysis of the cell walls and cytoplasm. The possibility that the initial cell of the developing syncytium or "prosyncyte" may influence a susceptible or resistant reaction is discussed. Successive stages of cell wall dissolution and the deposition of secondary cell walls are described.     

龙眼果实采后果肉自溶过程中细胞壁组分及其降解酶活性的变化

在(10±1)℃下贮藏的‘福眼’龙眼果实果肉自溶指数和自溶程度随着贮藏时间的延长而增加。果肉细胞壁干重、原果胶、纤维素、半纤维素和细胞壁蛋白含量不断减少。果肉果胶酯酶(PE)活性下降;多聚半乳糖醛酸酶(PG)活性在贮藏6～12d以及纤维素酶活性在贮藏0～12d期间均明显增强,到第12天达到活性高峰,之后下降。但在贮藏0～24d期间,PE、PG和纤维素酶仍然保持较高活性,贮藏24d之后快速下降。β-半乳糖苷酶活性在贮藏0～24d期间略有下降,而在贮藏24d后,活性增强,尤其是贮藏30d后,活性急剧升高。     

A leucine-rich repeat region is conserved in pollen extensin-like (Pex) proteins in monocots and dicots

We previously isolated a pollen-specific gene encoding a pollen tube wall-associated glycoprotein with a globular domain and an extensin domain from maize (mPex1). To evaluate which protein domains might be important for function, we isolated a second monocot gene (mPex2) and a dicot gene (tPex). Each gene encodes a signal sequence, an N-terminal globular domain comprised of a variable region, a leucine-rich repeat (LRR) with an adjacent cysteine-rich region, a transition region and an extensin-like C-terminal domain. The LRRs of the maize and tomato Pex proteins are highly conserved. Although the extensin domains in the maize and tomato proteins vary in length and in amino acid sequence, they are likely to be structurally conserved. Additional putative Pex gene sequences were identified by either GenBank search (Arabidopsis) or PCR (sorghum and potato); all encode conserved LRRs. The presence of a conserved LRR in the known and potential Pex proteins strongly suggests that this motif is involved in the binding of a specific ligand during pollen tube growth. Gene expression studies using RNA and protein blotting as well as promoter-reporter gene fusions in transient and stable transformation indicate that the tomato Pex gene is pollen-specific.     

Structural investigation of an arabinan from cabbage (Brassica oleracea var. capitata)

An arabinan has been isolated from the hot water-soluble pectic substances of cabbage cell wall material. Methylation analysis involving GC-MS of methylated alditol acetates formed from the methylated arabinan has shown that the parent polysaccharide is highly branched and of the same structural type as other arabinans associated with seed pectins.     

Down-regulation of an Auxin Response Factor in the tomato induces modification of fine pectin structure and tissue architecture

It has previously been shown that down-regulation of an auxin response factor gene (DR12) results in pleiotropic phenotypes including enhanced fruit firmness in antisense transgenic tomato (AS-DR12). To uncover the nature of the ripening-associated modifications affecting fruit texture, comparative analyses were performed of pectin composition and structure in cell wall pericarp tissue of wild-type and AS-DR12 fruit at mature green (MG) and red-ripe (RR) stages. Throughout ripening, pectin showed a decrease in methyl esterification and in the content of galactan side chains in both genotypes. At mature green stage, pectin content in methyl ester groups was slightly higher in AS-DR12 fruit than in wild type, but this ratio was reversed at the red-ripe stage. The amount of water- and oxalate-soluble pectins increased at the red-ripe stage in the wild type, but decreased in AS-DR12. The distribution of methyl ester groups on the homogalaturonan backbone differed between the two genotypes. There was no evidence of more calcium cross-linked homogalacturan involved in cell-to-cell adhesion in AS-DR12 compared with wild-type fruit. Furthermore, the outer pericarp contains higher proportion of small cells in AS-DR12 fruit than in wild type and higher occurrence of (1-->5) alpha-L-arabinan epitope at the RR stage. It is concluded that the increased firmness of transgenic fruit does not result from a major impairment of ripening-related pectin metabolism, but rather involves differences in pectin fine structure associated with changes in tissue architecture.     

Peroxidase isozyme patterns in the skin of maturing tomato fruit

The cessation of tomato fruit growth is thought to be induced by an increase in the activity of enzymes which rigidify cell walls in the fruit skin. Peroxidase could catalyse such wall‐stiffening reactions, and marked rises in peroxidase activity were recently reported in skin cell walls towards fruit maturity. Peroxidase isoforms in the fruit are here analysed using native gel electrophoresis. New isoforms of apparent M_r 44, 48 and 53 kDa are shown to appear in cell walls of the fruit skin at around the time of cessation of growth. It is inferred that these isozymes are present in the cell wall in vivo. Fruit from a range of non‐ripening mutants were also examined. Some of these do not soften or ripen for many weeks after achieving their final size. The new isozymes were found in skin cell walls of mature fruit in each of these mutants, as in the wild‐type and commercial varieties. It is concluded that the late‐appearing isozymes are not associated with fruit ripening or softening, and are probably not ethylene‐induced. They may act to control fruit growth by cross‐linking wall polymers within the fruit skin, thus mechanically stiffening the walls and terminating growth.     

Regulation of cell-wall polysaccharide components by CaCl2 in suspension cultures of kidney bean (Phaseolus vulgaris)

We cultured the suspension cells of kidney bean in MS media supplemented with one of five concentrations of CaCI₂ [0,22,44 (control), 88, or 176 mg/L], and harvested them at the logistic (15 d) and early-stationary (30 d) phases. Cells grown at concentrations higher than 22 mg/L showed better proliferation than those at 0 mg/L The rate of proliferation also increased with higher concentrations. We fractionated the individual sugars into symplastic (EtOH and starch) and apoplastic (low-molecular pectin, high-molecular pectin, hemicellulose, and cellulose) components. Cells treated at the highest concentration (176 mg/L) exhibited the greatest amount of sugar in the EtOH and starch fraction during the logistic phase. In contrast, cells in the early stationary phase had the highest level of sugar at treatment concentrations of less than 22 mg/L. For treatment concentrations higher than 22 mg/L on Day 15, more pectin and hemicellulose was detected at greater amounts compared with those cells treated with 0 mg/L. However, at Day 30, concentrations higher than 44 mg/L induced greater amounts of pectin and hemicellulose than from the other concentrations. Cellulose was more abundant with the 0 mg/L treatment, and contents ranged from 17.4 to 25.5% in the primary cell walls over all treatment concentrations. These results indicate that CaCI₂ modulates both symplastic and apoplastic sugar metabolism. Therefore, we suggest that the cell-wall structure may define the mode of polysaccharide biosynthesis during cell growth.