Suppressive effect of abscisic acid on systemic acquired resistance in tobacco plants

Recent studies have indicated that the phytohormone abscisic acid (ABA), induced in response to a variety of environmental stresses, plays an important role in modulating diverse plant–pathogen interactions. In Arabidopsis thaliana, we previously clarified that ABA suppressed the induction of systemic acquired resistance (SAR), a plant defense system induced by pathogen infection through salicylic acid (SA) accumulation. We investigated the generality of this suppressive effect by ABA on SAR using tobacco plants. For SAR induction, we used 1,2-benzisothiazole-3(2H)-one 1,1-dioxide (BIT) and benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester (BTH) that activate upstream and downstream of SA in the SAR signaling pathway, respectively. Wild-type tobacco plants treated with BIT or BTH exhibited enhanced disease resistance against Tobacco mosaic virus (TMV) and tobacco wildfire bacterium, Pseudomonas syringae pv. tabaci (Pst), however, which was suppressed by pretreatment of plants with ABA. Pretreatment with ABA also suppressed the expression of SAR-marker genes by BIT and BTH, indicating that ABA suppressed the induction of SAR. ABA suppressed BTH-induced disease resistance and pathogenesis-related (PR) gene expression in NahG-transgenic plants that are unable to accumulate SA. The accumulation of SA in wild-type plants after BIT treatment was also suppressed by pretreatment with ABA. These data suggest that ABA suppresses both upstream and downstream of SA in the SAR signaling pathway in tobacco.     

First report of plum pox virus infecting Japanese apricot (<Emphasis Type="Italic">Prunus mume</Emphasis> Sieb. et Zucc.) in Japan

For the first time, plum pox virus (PPV) has been detected in commercial Japanese apricot (Prunus mume) trees in Tokyo, Japan. These trees had ringspot or mottle on leaves, color breaking of petals and, occasionally, mild ringspots and malformation on fruits. The virus was identified based on the morphology of virus particles, serology, and RT-PCR. The amplified nucleotide fragment shared 100% identity with a partial coat protein gene of PPV-D isolates.     

First report of Choanephora rot of ice plant (<Emphasis Type="Italic">Mesembryanthemum crystallinum</Emphasis>) caused by <Emphasis Type="Italic">Choanephora cucurbitarum</Emphasis> in Japan

In summer 2007, leaf and stem rot of ice plants was found in a hydroponic greenhouse in Japan. The causal agent was a fungus identified as Choanephora cucurbitarum (Berkeley & Ravenel) Thaxter, based on pathogenicity, morphology, mating tests, and sequence analysis of the ribosomal DNA ITS region.     

Identification and crop performance of acid sulfate soil-tolerant rice varieties

The present study aims to: 1) identify acid sulfate soil (ASS)-tolerant rice varieties from the genetic stock of Korean rice (Oryza sativa L.) varieties under ASS conditions; 2) to evaluate their yield performance, and elucidate the physiological mechanism for ASS tolerance with the identified tolerant varieties. Two hundred sixty-six rice varieties were screened for ASS tolerance, and we identified two japonica-indica hybrid varieties, Geumgang (GG) and Pungsan (PS), as having high tolerance under ASS paddy conditions (pH 3). We first conducted a yield trial of GG and PS grown in Wagner pots to determine their potential yields under ASS conditions. A yield trial under paddy field condition followed. In the pot experiment, the ASS-tolerant varieties, GG and PS, showed significantly higher yields than PT-1, which is a local reference variety in mildly improved soil pH conditions (pH 4.1–4.6). Al and Fe content in GG and PS were significantly lower than that of PT-1, so there might be some mechanism that inhibits the absorption of toxic metal ions in the tolerant varieties. In the paddy conditions, the grain yields more than 5 t ha⁻¹ of the two tolerant varieties under mildly improved soil pH condition were significantly higher than PT-1. Dry matter weights of above ground parts also showed the same trend as grain yield. The study demonstrated that the ASS-tolerant japonica-indica rice varieties with high yielding potential could contribute to the improvement of rice yield in ASS regions, and will be good materials for the development of acid soil-tolerant rice varieties.     

Antagonism between acibenzolar-S-methyl-induced systemic acquired resistance and jasmonic acid-induced systemic acquired susceptibility to Colletotrichum orbiculare infection in cucumber

In cucumber, we show salicylic acid only induce local acquired resistance (LAR), whereas acibenzolar-S-methyl (ASM) can induce LAR and systemic acquired resistance (SAR) to plant diseases. Jasmonic acid (JA) can induce local acquired susceptibility (LAS) and systemic acquired susceptibility (SAS). ASM treatment of lower first leaves leads to the accumulation of cucumber acidic class III chitinase (CHI2) in untreated upper leaves and effectively suppresses lesion formation on those leaves. In contrast, JA treatment completely suppresses CHI2 gene expression and causes plants to be more susceptible to Colletotrichum orbiculare. ASM-induced SAR can effectively antagonize the JA-induced SAS, providing a response that is midway between what would be expected with either JA or ASM by themselves.     

Occurrence of azoxystrobin‐resistant isolates in Passalora fulva,the pathogen of tomato leaf mould disease

Since 2007, serious damage to tomato from leaf mould caused by Passalora fulva has frequently been observed in commercial greenhouses in Gifu Prefecture, Japan. One of the factors relating to this damage was suspected to be a decrease in azoxystrobin sensitivity of the pathogen. Biological and molecular studies were conducted to characterize fungicide resistance. In in vitro sensitivity tests using mycelial homogenate placed on fungicide‐amended medium, the minimum inhibitory concentrations (MIC) of azoxystrobin for mycelial growth of the isolates divided into two ranges, 0.031–0.5 mg L^?1 and 8–32 mg L^?1. Isolates with MICs within the two ranges were considered as sensitive and resistant, respectively, to azoxystrobin because, in in vivo tests, the percentage protection conferred by this fungicide (100 mg a.i. L^?1) against these isolates was 89.7–100% and 4.5–31.1%, respectively. Resistant isolates had a replacement of phenylalanine with leucine at codon 129 (F129L) in cytochrome b. Forty‐five percent of the 271 isolates collected from 63 tomato greenhouses from 2007 to 2008 were resistant to azoxystrobin. In many greenhouses where the isolation frequency of resistant isolates was 80% or more, azoxystrobin had been used twice per crop for approximately 6 years. In 2012, 27% of the 405 isolates collected were resistant to azoxystrobin, and there was a marked difference in the frequency of occurrence of resistant isolates in the field populations between the three locations sampled. The occurrence of azoxystrobin‐resistant P. fulva isolates (F129L mutants) inflicted considerable damage on greenhouse tomatoes.     

SEM observations on larval shell morphology of Manila clam Ruditapes philippinarum and their utility

Manila clam Ruditapes philippinarum is common and abundant on Japanese tidal flats, forming a commercially important clam fishery. However, annual catches of Manila clam have decreased drastically since 1975?C1985. To study larval recruitment processes of Manila clam, we carried out scanning electron microscopy (SEM) observations on larval and juvenile shells of clams reared at 20 and 24?°C. There was no significant difference in final shell length of trochophores between 20 and 24?°C. However, the larval duration was much longer and the shell length of settled size of pediveligers was much larger for clams reared at 20?°C than those reared at 24?°C. These findings suggest that larval duration and growth, as well as settlement size, may vary markedly depending on temperature (and probably on season). The larval shell morphology of Manila clam can provide essential information about larval recruitment processes.     

Influence of parity and litter size on gestation length in beagle dogs

This study was conducted to investigate the effects of parity and litter size on gestation length in beagle bitches. The mean duration of the initial elevation (>2 ng/mL) in progesterone concentrations after the onset of proestrus was shorter (P < 0.05) in bitches without (nulliparous) whelping experience than in bitches with (multiparous) whelping experience (6.9 d versus 8.0 d). When calculated as the interval between the day of initial elevation in progesterone concentrations and the day of whelping, the gestation length in the nulliparous bitches was noted to be similar to that in the multiparous bitches (64.3 d versus 64.2 d). No significant correlation between gestation length and litter size was observed in any of the bitches. Our results indicate that the gestation length in beagle bitches is not affected by parity or litter size.     

Physiological and ecological implications of adaptive reiteration as a mechanism for crown maintenance and longevity

Reiteration is the process whereby architectural units are replicated within a tree. Both immediate (from apical buds) and delayed (from suppressed or adventitious buds) reiteration can be seen in many tree species where architectural units ranging from clusters of shoots to entire branches and stems are replicated. In large old trees and suppressed trees, delayed reiteration occurs without an obvious external stimulus such as defoliation or traumatic loss of the branch apex. This suggests that, in trees that are growth-limited, reiteration is an adaptive mechanism for crown maintenance. We discuss theories about the aging process and how delayed adaptive reiteration may help maintain crown productivity and increase longevity. These include: (1) reducing the respiration/photosynthesis ratio; (2) increasing hydraulic conductance to newly developing foliage; (3) reducing nutrient loss from the tree; and (4) rejuvenating the apical meristem. The ability to reiterate various architectural units may contribute to increasing lifetime reproductive output by prolonging tree longevity. Further studies on the physiological and ecological implications of reiteration are needed to understand its adaptive significance in the life history of trees.     

Choice of statistical model for estimating genetic parameters using restricted maximum likelihood in swine

Summary Restricted maximum likelihood (REML) was used to determine the choice of statistical model, additive genetic maternal and common litter effects and consequences of ignoring these effects on estimates of variance–covariance components under random and phenotypic selection in swine using computer simulation. Two closed herds of different size and two traits, (i) pre‐weaning average daily gain and (ii) litter size at birth, were considered. Three levels of additive direct and maternal genetic correlations (r_dm) were assumed to each trait. Four mixed models (denoted as GRM1 through GRM4) were used to generate data sets. Model GRM1 included only additive direct genetic effects, GRM2 included only additive direct genetic and common litter effects, GRM3 included only additive direct and maternal genetic effects and GRM4 included all the random effects. Four mixed animal models (defined as EPM1 through EPM4) were defined for estimating genetic parameters similar to GRM. Data from each GRM were fitted with EPM1 through EPM4. The largest biased estimates of additive genetic variance were obtained when EPM1 was fitted to data generated assuming the presence of either additive maternal genetic, common litter effects or a combination thereof. The bias of estimated additive direct genetic variance (VA_d) increased and those of recidual variance (VE) decreased with an increase in level of r_dm when GRM3 was used. EPM1, EPM2 and EPM3 resulted in biased estimation of the direct genetic variances. EPM4 was the most accurate in each GRM. Phenotypic selection substantially increased bias of estimated additive direct genetic effect and its mean square error in trait 1, but decreased those in trait 2 when ignored in the statistical model. For trait 2, estimates under phenotypic selection were more biased than those under random selection. It was concluded that statistical models for estimating variance components should include all random effects considered to avoid bias.