High‐throughput two‐dimensional root system phenotyping platform facilitates genetic analysis of root growth and development

High‐throughput phenotyping of root systems requires a combination of specialized techniques and adaptable plant growth, root imaging and software tools. A custom phenotyping platform was designed to capture images of whole root systems, and novel software tools were developed to process and analyse these images. The platform and its components are adaptable to a wide range root phenotyping studies using diverse growth systems (hydroponics, paper pouches, gel and soil) involving several plant species, including, but not limited to, rice, maize, sorghum, tomato and Arabidopsis. The RootReader2D software tool is free and publicly available and was designed with both user‐guided and automated features that increase flexibility and enhance efficiency when measuring root growth traits from specific roots or entire root systems during large‐scale phenotyping studies. To demonstrate the unique capabilities and high‐throughput capacity of this phenotyping platform for studying root systems, genome‐wide association studies on rice (Oryza sativa) and maize (Zea mays) root growth were performed and root traits related to aluminium (Al) tolerance were analysed on the parents of the maize nested association mapping (NAM) population.     

Host response of rice genotypes to the rice root-knot nematode (Meloidogyne graminicola) under aerobic soil conditions

Aerobic rice is a production system where adapted rice varieties are established via direct seeding in non-puddled, non-flooded, non-saturated fields and grown under conditions similar to upland conditions. On land cultivated continuously with aerobic rice, a yield reduction has been observed. The rice root-knot nematode Meloidogyne graminicola is considered one of the possible causes of these yield reductions. Resistance to and tolerance for M. graminicola are essential traits for aerobic rice cultivars in alleviating this problem. In our study, the host response of nineteen aerobic, seven upland and four lowland rice genotypes which are either being used in the International Rice Research Institute’s aerobic rice breeding programme or already cultivated by farmers in Asia was evaluated under aerobic soil conditions in an outdoor raised-bed experiment. Our study showed a large variation in susceptibility and sensitivity to M. graminicola infection among the rice genotypes examined. Resistance comparable to the resistant reference genotypes included in the experiment (CG14, TOG5674, TOG7235) was not found but in terms of susceptibility, the upland genotype Morobereken may be an interesting less-susceptible genotype. Tolerance was found and in terms of sensitivity, the high yielding aerobic genotype IR78877-208-B-1-2 may be an interesting tolerant genotype. Our study also allowed the identification of rice genotypes that are either highly susceptible or sensitive to M. graminicola infection and of which the cultivation should be discouraged. On average, M. graminicola caused an almost 30% reduction in yield. Excluding the two susceptible and three resistant reference genotypes included in the experiment, most affected was dry-shoot biomass (23.6% reduction) followed by root length, which was more affected than fresh-root weight (19.8 vs. 8%) and grain filling (17.3%), while plant height and the number of spikelets/panicle were less affected (10.2 and 8.1%, respectively). Neither tillering nor the number of panicles/plant were affected.     

Xanthomonas oryzae pv. oryzae infection triggers accumulation of phenolics,defense-related enzymes and thaumatin-like proteins in rice leaves

Abstract

The effect of Xanthomonas oryzae pv. oryzae infection on induction of phenylalanine ammonia-lyase (PAL), peroxidase (PO), phenolics and thaumatin-like proteins (TLPs) in rice was studied. PAL activity increased significantly one day after inoculation with X. o. pv. oryzae and the maximum enzyme activity was observed two days after inoculation. The phenolic content in rice leaves increased significantly one day after inoculation and the maximum accumulation of phenols was observed two days after inoculation. Significant increase in peroxidase activity was observed in rice leaves one day after inoculation with X. o. pv. oryzae. Isozyme analysis indicated that three peroxidase isozymes (PO-1, PO-2 and PO-3) were induced after inoculation with X. o. pv. oryzae. Immunoblot analysis of protein extracts from control and pathogen inoculated rice plants revealed the induced accumulation of 16 and 24 kDa TLPs in rice leaves in response to X. o. pv. oryzae infection. TLP mRNA accumulation was induced strongly in rice leaves in response to infection by X. o. pv. oryzae.     

A scanning electron microscope study of ectodermal differentiations in the caudal mantle epithelium of embryos and juveniles of Loligo vulgaris,Loligo forbesi and Sepia officinalis

Summary

The mantle epithelium of embryos and early juveniles of the squids Loligo vulgaris and Loligo forbesi and the cuttlefish Sepia officinalis was studied using scanning electron microscopy. In embryos of L. vulgaris and L. forbesi, previously undescribed epidermal structures were found. They are missing in S. officinalis embryos. These so-called “extruding structures” are located near Hoyle's organ and first appear at stage XIII of Naef. At the same embryonic stage, Hoyle's organ starts to differentiate and “uniform-type” ciliated cells become visible in the epidermis of both L. vulgaris and L. forbesi. Directly after hatching the epidermis of the species examined starts to slough off and finally the extruding structures, Hoyle's organ and both types of ciliated cells of the mantle epithelium disappear. The function of the extruding structures remains obscure.     

The acclimation of leaf photosynthesis of wheat and rice to seasonal temperature changes in T‐FACE environments

Crops show considerable capacity to adjust their photosynthetic characteristics to seasonal changes in temperature. However, how photosynthesis acclimates to changes in seasonal temperature under future climate conditions has not been revealed. We measured leaf photosynthesis (A_n) of wheat (Triticum aestivum L.) and rice (Oryza sativa L.) grown under four combinations of two levels of CO₂ (ambient and enriched up to 500 µmol/mol) and two levels of canopy temperature (ambient and increased by 1.5–2.0°C) in temperature by free‐air CO₂ enrichment (T‐FACE) systems. Parameters of a biochemical C₃‐photosynthesis model and of a stomatal conductance (g_s) model were estimated for the four conditions and for several crop stages. Some biochemical parameters related to electron transport and most g_s parameters showed acclimation to seasonal growth temperature in both crops. The acclimation response did not differ much between wheat and rice, nor among the four treatments of the T‐FACE systems, when the difference in the seasonal growth temperature was accounted for. The relationships between biochemical parameters and leaf nitrogen content were consistent across leaf ranks, developmental stages, and treatment conditions. The acclimation had a strong impact on g_s model parameters: when parameter values of a particular stage were used, the model failed to correctly estimate g_s values of other stages. Further analysis using the coupled g_s–biochemical photosynthesis model showed that ignoring the acclimation effect did not result in critical errors in estimating leaf photosynthesis under future climate, as long as parameter values were measured or derived from data obtained before flowering.     

六个核基因片段在中国颗粒野生稻中的单核苷酸多态性及其在群体遗传学研究中的应用

为了筛选可用于亚洲栽培稻的重要野生近缘物种颗粒野生稻群体遗传结构研究的有效SNPs标记,本研究共选取Osgstf3、OsNAC6、BADH、XCP2、EMF2和ERCC4 6个重要水稻功能基因,检测了来自中国云南和海南12份颗粒野生稻代表样品中的单核苷酸多态性,结果发现Osgstf3、OsNAC6、BADH和XCP2的单核苷酸多态性接近于零,但在EMF2和ERCC4内含子区中检测到较低的核苷酸变异。利用EMF2和ERCC4片段对来自云南的3个天然群体和来自海南的2个天然群体共52个个体进行了群体遗传学研究,发现该物种具有高水平的遗传分化和低水平的遗传变异的独特群体遗传结构;这种剧烈的遗传分化不仅来自云南和海南两个地区之间,而且还来自地区内居群间,说明该野生稻生长的热带、亚热带森林生境的破坏导致了碎裂的居群间基因流强烈受阻。     

Attractiveness of synthetic volatile blends of flowering rice panicles to Trigonotylus caelestialium (Kirkaldy) (Heteroptera: Miridae)

The attractiveness of 22 synthetic volatile blends or seven individual chemicals emitted from flowering rice panicles to a rice leaf bug, Trigonotylus caelestialium (Kirkaldy), were investigated with an olfactometer to identify the active compounds responsible for the invasion of the bugs into paddy fields. n‐Decanal attracted only male bugs, whereas β‐caryophyllene attracted only females. β‐Elemene repelled males and methyl benzoate marginally repelled females. The other chemicals did not attract or repel male and female bugs at all. Two‐, 3‐, 4‐ and 5‐component blends of β‐caryophyllene, n‐decanal, n‐tridecene, methyl salicylate and geranyl acetone were attractive to neither females nor males. Two‐component blends comprised of β‐caryophyllene and methyl salicylate, or n‐decanal and methyl salicylate, marginally repelled females. The three‐component blend comprised of β‐caryophyllene, n‐decanal and geranyl acetone marginally repelled females. The five‐component blend comprised of β‐caryophyllene, n‐decanal, n‐tridecene, methyl salicylate and geranyl acetone repelled males. The seven‐component blend comprised of β‐caryophyllene, n‐decanal, n‐tridecene, methyl salicylate, geranyl acetone, methyl benzoate and β‐elemene attracted female bugs and marginally attracted male bugs. Six‐component blends without any one of these seven components were not attractive to the bugs although the six‐component blend without n‐decanal was marginally attractive to females. The six‐component blend without n‐tridecene repelled males. These findings suggest that mixtures of these seven compounds play an important role in the attractiveness of flowering rice panicles to both sexes of the bugs, although the attractiveness of individual compounds differs between sexes.     

The influence of rice plant age on susceptibility to the rice water weevil,Lissorhoptrus oryzophilus

Plant age‐ and plant stage‐related changes in the resistance of rice, Oryza sativa, to its most important insect pest in the US, the rice water weevil (Lissorhoptrus oryzophilus), were investigated in a series of field and greenhouse choice and no‐choice studies. Rice plants were susceptible to infestation by rice water weevils over a broad range of plant ontogenetic stages, from at least the early vegetative stage to well into the reproductive stage. There was, however, a clear preference expressed by rice water weevils in both choice and no‐choice experiments for plants in (or nearly in) the tillering stage of development, with pre‐tillering and reproductive stage plants less preferred. The relationship between rice plant age and susceptibility to weevils is thus nonlinear. This study constitutes one of the most thorough studies to date of the relationship in a grass species between plant age and susceptibility to herbivores. The results provide a biological explanation for observed patterns of weevil infestations and a rationale for the cultural practice of delayed flooding.     

Fermentative Production of l-Proline with Auxotrophs of Corynebacterium glutamicum

Two auxotrophic mutants of Corynebacterium glutamicum were found to produce a large amount of l-proline in the culture medium. High concentration of MgSO₄ or MnSO₄ in the medium stimulated the l-proline production by an isoleucine auxotroph. Optimum concentration of l-isoleucine was 200 μg/ml, and the higher concentration of l-isoleucine reduced the l-proline production. The auxotroph produced 14.8 mg/ml of l-proline when cultured in a medium containing 12% glucose, 1.7% NH₄C1,0.6% MgSO₄·7H₂O, 0.06% MnSO₄·4H₂O and 200 μg/ml of l-isoleucine. The other mutant, whose growth responds to the bases of nucleic acids, produced 7 to 13 mg/ml of l-proline in a cane molasses (15%, as glucose concentration)-medium containing 2% of the acid-hydrolyzate of soybean meal. The l-proline production by this mutant increased to a level of 27 to 31 mg/ml when the growth was suppressed by the addition of 4% NH₄C1 to the medium, or by the addition of 2 mg/ml of polyoxyethylenestearylamine, a surfactant, to a culture at an appropriate stage of the fermentation.     

Change of the Structure of Cell Wall β-l,3-d-Glucan with the Growth of Neurospora crassa Cells

The chemical structure of cell wall β-d-glucans as well as the activities of lytic enzymes such as β-1,3-d-glucanase and β-1,6-d-glucanase changed during the growth of Neurospora crassa.

A dramatic change in the cell wall β-d-glucan structure was observed between cells of the middle logarithmic phase and ones of the late logarithmic phase. The ratio of 1,3-linked glucose residues to non reducing terminal glucose residues decreased from 85 to 55 and the ratio of gentiobiose as a hydrolysis product with exo-β-1,3-d-glucanase increased significantly between the two phases.

Two prominent peaks of β-1,3-d-glucanase as well as the β-1,6-d-glucanase activities appeared in the culture filtrate at different growth stages, the early logarithmic phase and the stationary phase. In the cell wall, β-d-glucosidase activity instead of the β-l,6-d-glucanase and β-1,3-d-glucanase activities was observed in the late logarithmic phase.