Multiplex PCR assay for simultaneous detection of MBI-D and Q<Subscript>o</Subscript>I resistance in rice blast fungus

For sustainable control of rice blast with fungicides, efficient monitoring of the emergence and spread of fungicide-resistant isolates is needed. We developed simple and reliable PCR-based DNA markers to detect isolates resistant to melanin biosynthesis inhibitor targeting scytalone dehydratase (MBI-D) and quinone outside inhibitor (Q_oI) fungicides. Through the use of DNA templates prepared from mycelia on filter paper or from infected leaves, these markers enable rapid (a few hours) genotyping of point mutations that confer resistance. The developed multiplex marker detected resistance to both MBI-D and Q_oI in a single PCR and further reduced the time needed for diagnosis.     

Five plant families support natural sporulation of <Emphasis Type="Italic">Cronartium ribicola</Emphasis> and <Emphasis Type="Italic">C. flaccidum</Emphasis> in Finland

Fusarium is one of the most destructive fungal genera whose members cause many diseases on plants, animals, and humans. Moreover, many Fusarium species secrete mycotoxins (e.g. trichothecenes and fumonisins) that are toxic to humans and animals. Fusarium isolates from date palm trees showing disease symptoms, e.g. chlorosis, necrosis and whitening, were collected from seven regions across Saudi Arabia. After single-sporing, the fungal strains were morphologically characterized. To confirm the identity of morphologically characterized Fusarium strains, three nuclear loci, two partial genes of translation elongation factor 1 α (tef1α) and β-tubulin (tub2), and the rDNA-ITS region, were amplified and sequenced. Of the 70 Fusarium strains, 70 % were identified as F. proliferatum that were recovered from six regions across Saudi Arabia. Fusarium solani (13 %), as well as one strain each of the following species: F. brachygibbosum, F. oxysporum, and F. verticillioides were also recovered. In addition, five Fusarium-like strains were recognized as Sarocladium kiliense by DNA-based data. The preliminary in vitro pathogenicity results showed that F. proliferatum had the highest colonization abilities on date palm leaflets, followed by F. solani. Although F. oxysporum f. sp. albedinis is the most serious date palm pathogen, F. proliferatum and F. solani are becoming serious pathogens and efforts should be made to restrict and control them. In addition, the potential toxin risks of strains belonging to F. proliferatum should be evaluated.     

Differential expression of molecular rust resistance components have distinctive profiles in <Emphasis Type="Italic">Coffea arabica</Emphasis> - <Emphasis Type="Italic">Hemileia vastatrix</Emphasis> interactions

Countering the economic hurdle caused by coffee leaf rust disease is most appealing at this time as it has posed a major threat to coffee production around the world. Establishing differential expression profiles at different times following pathogen invasion in both innate and acquired immunities unlocks the molecular components of resistance and susceptibility. Suppression subtractive hybridization (SSH) was used to identify genes differentially over-expressed and repressed during incompatible and compatible interactions between Coffea arabica and Hemileia vastatrix. From 433 clones of expressed sequence tags (ESTs) sequenced, 352 were annotated and categorized of which the proportion of genes expressed during compatible interaction were relatively smaller. The result showed upregulation and downregulation of various genes at 12 and 24 h after pathogen inoculation in both interactions. The use of four different databases in searching for gene homology resulted in different number of similar sequences. BLASTx against EMBL-EBI (European Molecular Biology Laboratory-European Bioinformatics Institute) database being with the maximum (100%) hits for all the annotated sequences. RT-qPCR analysis of seven resistance-signaling genes showed similar expression patterns for most of the genes in both interactions, indicating these genes are involved in basal (non-specific) defense during which immune reactions are similar. Using SSH, we identified different types of resistance related genes that could be used for further studies towards resistant cultivar development. The potential role of some of the resistance related proteins found were also discussed.     

Recovery of fungicide-resistant <Emphasis Type="Italic">Botrytis</Emphasis> isolates from strawberry nursery plants

In a four-year survey of strawberry nursery plants, 340 Botrytis isolates were collected and examined for fungicide resistance. High percentages of isolates with resistance to members of all fungicide classes registered on strawberries in Germany were found, i.e. trifloxystrobin (90.3%), boscalid (53.8%), cyprodinil (41.5%), fludioxonil (28.2%) and fenhexamid (15.6%). Of these isolates, 10.3% possessed multiple resistance to all compounds. At 5.0%, resistance to the recently registered fungicide fluopyram was low. Dutch nursery material harboured significantly higher proportions of isolates with resistance to any or all fungicides than plants produced in Germany. These data point to nursery plants as a possible route of introducing fungicide-resistant Botrytis strains into commercial strawberry fields.     

Pheromone Research and Development in Israel 1975–2015

The review describes the history of pheromone research in Israel in 1975–2015. The research focused on sex pheromones of moths that were important agricultural pests. Identification, synthesis and field application of sex pheromones was performed. Synthetic procedures of several known sex pheromones were developed. Monitoring and control of key pest moths was evaluated. The interactions of pheromone components of closely related species were studied in field and laboratory experiments. The sex pheromones of three scale insects, two mealybug species and Matsucoccus josephi were studied. New syntheses were developed and the pheromones were implemented in pest management. Structure activity relationship of the pheromonal and kairomonal of the M. josephi pheromone was investigated. Different pherotypes of P. ficus were identified and evaluated. The aggregation pheromone of sap beetles in combination with food baits was evaluated. The aggregation pheromone of the almond bark beetle was identified and a stereospecific synthesis of its enantiomers was developed. Monitoring the pest in stone fruit orchards was implemented. The activity of the pheromone biosynthesis activating neuropeptide (PBAN) was studied in Helicoverpa armigera and Heliothis peltigera. The ligation technique was used to assess the effect of PBAN on the production of female and male pheromones. A structure-activity relationship study of PBAN indicated that shorter peptides display activity as the full length PBAN. A series of linear and cyclic peptide analogs was prepared, resulting in the discovery of a lead antagonist. The research and development activity facilitated the intensive integration of pheromones in the pest management regimes in Israeli agriculture.     

Genetic resistance to bacterial blight disease in Persian walnut

Bacterial blight disease of Persian walnut (Juglans regia, L.), caused by Xanthomonas arboricola pv. juglandis (Xaj), leads to significant nut losses in northern, central and western areas of Iran. To identify the natural sources of resistance to disease in the endemic walnut genotypes of Iran, sixteen walnut genotypes, collected from different areas of Hamedan province, were inoculated with Xaj in a randomized complete block design with five replicates for each genotype. Two-year old genotypes were gently sprayed with a suspension of bacteria adjusted to approximately 2 × 10⁹ cfu ml⁻¹ of distilled water in May. Infected leaves were rated for disease 28 and 42 days after inoculation, using a 0 to 5 severity scale, based on the number, size and distribution of lesions on the leaves. Data analyses showed that there were variations among genotypes in response to pathogen. Upon inoculation by bacterial suspension genotype 94 showed the highest resistance to both disease incidence and its progress after 4–6 weeks of infection. Genotype 65 showed high susceptibility to disease and genotype 69 showed high susceptibilities both to disease incidence and its progress after 4–6 weeks of infection.     

Spread of seed-borne <Emphasis Type="Italic">Erwinia rhapontici</Emphasis> in bean,pea and wheat

Studies were conducted in the laboratory and greenhouse to determine the distribution of Erwinia rhapontici in plants arising from naturally infected seeds of pea or artificially inoculated seeds of bean and wheat, and whether the pathogen is transmitted to the subsequent generation of seeds. Infected seeds were planted in pots of Cornell mix in the greenhouse, and sampled at specified intervals throughout the plant growth cycle (seedling stage, elongation stage, flowering stage, seed formation stage, and maturity). Plating of surface sterilized lateral roots, tap roots, basal stems, mid-stems, apical stems, petioles, pods, and seeds of pea and bean, and of lateral roots, sub-crown internodes, basal stems, mid-stems, apical stems, peduncles, glumes, and seeds of wheat revealed that the bacterial pathogen spread from infected seeds to the lower parts of the plant tissues, but failed to spread further to the seeds produced on these plants. The study concludes that E. rhapontici did not establish systemic infection throughout the plants. Possible mechanisms of infection of seeds are discussed.     

Identification of quantitative trait loci for agronomic and physiological traits in maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) under high-nitrogen and low-nitrogen conditions

Low-nitrogen (LN) tolerance is a compound character with a complex genetic basis. Many agronomic traits have been shown to be closely related to LN tolerance in maize. In this study, 150 F₇ recombinant inbred lines derived from a cross between inbreds 178 and K12 were evaluated for agronomical and physiological traits under high-nitrogen (HN) and LN conditions in 2 years. Inclusive composite interval mapping (ICIM) was used to identify the quantitative trait loci (QTLs) for traits recorded under different treatments (LN and HN) in 2 years. In total, 86 QTLs were detected: 38 for HN and 35 for LN, while 13 QTLs were detected under both nitrogen levels, suggesting that LN-specific QTLs may play a role in improving LN tolerance in maize. Overlapping QTLs for different traits were located on all chromosomes except chromosome 4 and chromosome 9. Many of these regions overlapped with previously reported QTLs. Several consensus major QTLs and LN-specific major QTLs found in the study can be used in marker-assisted selection breeding for genetic improvement and LN tolerance in maize in the future.     

Capturing genetic variability and selection of traits for heat tolerance in a chickpea recombinant inbred line (RIL) population under field conditions

Chickpea is the most important pulse crop globally after dry beans. Climate change and increased cropping intensity are forcing chickpea cultivation to relatively higher temperature environments. To assess the genetic variability and identify heat responsive traits, a set of 296 F_8–9 recombinant inbred lines (RILs) of the cross ICC 4567 (heat sensitive) × ICC 15614 (heat tolerant) was evaluated under field conditions at ICRISAT, Patancheru, India. The experiment was conducted in an alpha lattice design with three replications during the summer seasons of 2013 and 2014 (heat stress environments, average temperature 35 °C and above), and post-rainy season of 2013 (non-stress environment, max. temperature below 30 °C). A two-fold variation for number of filled pods (FPod), total number of seeds (TS), harvest index (HI), percent pod setting (%PodSet) and grain yield (GY) was observed in the RILs under stress environments compared to non-stress environment. A yield penalty ranging from 22.26% (summer 2013) to 33.30% (summer 2014) was recorded in stress environments. Seed mass measured as 100-seed weight (HSW) was the least affected (6 and 7% reduction) trait, while %PodSet was the most affected (45.86 and 44.31% reduction) trait by high temperatures. Mixed model analysis of variance revealed a high genotypic coefficient of variation (GCV) (23.29–30.22%), phenotypic coefficient of variation (PCV) (25.69–32.44%) along with high heritability (80.89–86.89%) for FPod, TS, %PodSet and GY across the heat stress environments. Correlation studies (r = 0.61–0.97) and principal component analysis (PCA) revealed a strong positive association among the traits GY, FPod, VS and %PodSet under stress environments. Path analysis results showed that TS was the major direct and FPod was the major indirect contributors to GY under heat stress environments. Therefore, the traits that are good indicators of high grain yield under heat stress can be used in indirect selection for developing heat tolerant chickpea cultivars. Moreover, the presence of large genetic variation for heat tolerance in the population may provide an opportunity to use the RILs in future-heat tolerance breeding programme in chickpea.     

Assessing Allelopathic Index for Estimating Allelopathic potential of Ajowan Extracts

Allelopathy is a procedure in which secondary metabolites are produced by plants. Some plants may beneficially or antagonistically affect other plants through allelochemical compounds which may be released directly or indirectly from live or dead parts and cause allelopathic and phytotoxic effects. The aim of the present study was to investigate the allelopathic possibility of ajowan (Carum copticum) extracts in different concentrations on morphological indices (germination and growth) of wheat (Triticum sativum), barley (Hurdeum vulgare), corn (Zea maize S.C 704), and safflower (Carthamus tinctorius L.) seedlings as proceeding crops and to develop a comprehensive formula for measuring the negative and positive effects of allelochemicals on growth indices such as shoot and root length, as well as the germination percentage on donor plants. It was demonstrated that increasing concentrations of ajowan extracts significantly decreased the Allelopathic Index, percent of germination, and other growth related indices of all seedlings. Based on the proposed Allelopathic Index of experimental plants, it was revealed that ajowan has posed a higher risk to corn and barley especially at the early stages of the growing cycle, while safflower and wheat indicated more tolerance to growth inhibition effects of ajowan in rotational sequence.