Fungistatic activity mediated by volatile organic compounds is isolate-dependent in Trichoderma sp. “atroviride B”

Trichoderma spp. produce multiple bioactive volatile organic compounds (VOCs). While the bioactivity of VOCs from different Trichoderma species is well documented, information on intraspecific variation is limited. The fungistatic activity of VOCs emitted by 59 Trichoderma sp. “atroviride B” isolates against the pathogen Rhizoctonia solani was investigated. Eight isolates representing the two extremes of bioactivity against R. solani were also assessed against Alternaria radicina, Fusarium oxysporum f. sp. lycopersici and Sclerotinia sclerotiorum. VOCs profiles of these eight isolates were analyzed using gas chromatography–mass spectrometry (GC-MS) to identify a correlation between specific VOCs and bioactivity, and 11 VOCs were evaluated for bioactivity against the pathogens. Bioactivity against R. solani varied among the fifty-nine isolates, with five being strongly antagonistic. All eight selected isolates inhibited the growth of all four pathogens, with bioactivity being lowest against F. oxysporum f. sp. lycopersici. In total, 32 VOCs were detected, with individual isolates producing between 19 and 28 VOCs. There was a significant direct correlation between VOC number/quantity and bioactivity against R. solani. 6-pentyl-α-pyrone was the most abundant VOC produced, but 15 other VOCs were also correlated with bioactivity. All 11 VOCs tested inhibited R. solani growth, some by >50%. Some of the VOCs also inhibited the growth of the other pathogens by >50%. This study demonstrates significant intraspecific differences in VOC profiles and fungistatic activity supporting the existence of biological diversity within Trichoderma isolates from the same species, a factor in many cases ignored during the development of biological control agents

Evaluation of Genetic Diversity in White Clover (\u3cem\u3eTrifolium Repens\u3c/em\u3e L.) Through Measurement of Simple Sequence Repeat (SSR) Polymorphism

White clover (Trifolium repens L.) is a key important temperate pasture legume. Due to the obligate outbreeding nature of white clover, individual genotypes within cultivars are highly genetically heterogeneous. Genetic diversity has been assessed within and between 16 elite cultivars derived from Europe, North and South America, New Zealand and Australia

Genetic Analysis of the Interaction Between Perennial Ryegrass and the Fungal Endophyte \u3cem\u3eNeotyphodium Lolii\u3c/em\u3e

The fungal endophyte Neotyphodium lolii is widely distributed in perennial ryegrass pastures, especially in Australia and New Zealand. The presence of the endophyte is associated with improved tolerance to water and nutrient stress and resistance to insect pests, but is accompanied by reduced herbivore feeding. The molecular mechanisms responsible for these endophyte-related traits are in general poorly understood. Comparisons of different grass-endophyte associations show that endophyte-related traits are affected by both endophyte and host genotype, and environmental interactions

Application of Molecular Technologies in Forage Plant Breeding

Key points A range of molecular breeding technologies have been developed for forage plant species including both transgenic and non-transgenic methodologies. The application of these technologies has the potential to greatly increase the range of genetic variation that is available for incorporation into breeding programs and subsequent delivery to producers in the form of improved germplasm. Further developments in detailing the phenotypic effect of genes and alleles both through research in target species and through inference from results from model species will further refine the delivery of new forage cultivars

Genetic Variation in the Perennial Ryegrass Fungal Endophyte \u3cem\u3eNeotyphodium Lolii\u3c/em\u3e

The common fungal endophytes (Neotyphodium species) of temperate pasture grasses are associated with improved tolerance to water and nutrient stress and resistance to insect pests, but are also the causal agents of animal toxicoses. Considerable variation exists among grass-endophyte associations for these beneficial and detrimental agronomic traits. The extent to which this variation may be attributed to the endophyte genotype, the host genotype or environmental interactions is currently unknown. The development of molecular genetic markers for endophytes based on simple sequence repeat (SSR) loci and the demonstration of the specific detection of endophytes in planta with these markers (van Zijll de Jong et al., 2005) allows efficient assessment of endophyte diversity in grass populations

Is induced systemic resistance the mechanism for control of black rot in Brassica oleracea by a Paenibacillus sp.?

© 2015 Elsevier Inc. Paenibacillus isolate P16 has been identified as a promising biological control agent for black rot (Xanthomonas campestris pv. campestris or Xcc) in cabbage (Brassica oleracea var. capitata). The mode of action of this isolate, in particular its ability to induce systemic resistance (ISR) in cabbage was investigated. Cabbage seedlings (2 and 4-weeks old) grown from seeds treated with isolate P16 were challenged with Xcc at two different concentrations, 1×10⁶, and 1×10⁹ CFU/ml. A reduction in disease severity was observed in P16-treated seedlings compared to the non-treated control when Xcc was injected into the leaves of 4-week old seedlings. Isolate P16 was not detected in the leaves of seedlings at the time of Xcc challenge. Based on the temporal and spatial separation for the P16 and Xcc applications, ISR appeared to be the mechanism underlying this disease reduction. The expression of seven defense-related genes (CAS, RubisCO, BIK1, COI1, EIN3, WRKY70, and PRB1) was studied in P16-treated and non-treated 4-week old cabbage seedlings injected with Xcc inoculum at 1×10⁶ CFU/ml. Despite evidence that biocontrol by P16 is via ISR, no changes were observed in the expression levels of these genes in P16-treated seedlings that had been challenged with Xcc. A differential response to wounding was detected. This study has provided a starting point for further research at the molecular level to better understand the apparent systemic resistance induced by P16 in cabbage in response to Xcc infection

Discovery of two Brevibacillus laterosporus isolates from brassica with insecticidal properties against diamondback moth

© 2016 Taylor & Francis. New biopesticides are required as diamondback moth (Plutella xylostella) develops field resistance to existing control measures. Following evaluation of 35 microbial isolates, 24 from brassica, two Brevibacillus laterosporus isolates were identified that caused mortality of larvae. Larval feeding declined with one isolate to levels comparable to that of Bacillus thuringiensis

Genetic diversity in the perennial ryegrass fungal endophyte Neotyphodium lolii

Expressed sequence tag (EST) data for the grass fungal endophyte species Neotyphodium lolii and N. coenophialum has been used to generate a comprehensive set of simple sequence repeat (SSR) markers for the genetic analysis of the grass-endophyte symbiosis. Initial analysis of reference isolates from the perennial ryegrass endophyte N. lolii revealed low levels of genetic variation. Twenty-two EST-SSR markers were assembled into multiplex panels for in planta detection and genetic polymorphism analysis of the endophyte. The markers were shown to be endophyte-specific and effective at low mass-ratios of endophyte to plant genomic DNA. Genetic variation has been assessed in plants obtained from a globally distributed perennial ryegrass germplasm collection, as well as from Australian farms with variable incidence of endophyte-dependent livestock toxicosis and a perennial ryegrass variety containing an endophyte associated with reduced toxic effects. The reference isolates span the majority of the observed genetic variation in this sample, suggesting that relatively little genetic variation is present within the species, and that quantitative variation for expression of endophyte characters may be more associated with host grass genotypic differences. The geographical pattern of diversity of European-derived endophytes shows some similarity with the distribution of chloroplast DNA haplotype in perennial ryegrass, as may be expected for symbionts with matrilinear inheritance. This data supports the model of a monophyletic origin for N. lolii and dispersion from the Near East associated with ancient human migrations