Plant genetic resources of Lemnos (Greece), an isolated island in the Northern Aegean Sea, with emphasis on landraces

Lemnos Island is located in the Northern Aegean Sea and presents a rich biodiversity in plant genetic resources including wild species and crop landraces. Landraces have been cultivated under traditional agricultural systems and many have survived genetic erosion. They are mainly conserved in home gardens or in small fields, usually by elderly people, and are limited to local consumption. Two collecting expeditions were organized in Lemnos, a minor one in 2009 and a larger one in 2010. The results of the two current expeditions are discussed and compared with previous expeditions in the island. An overview is given on the crops cultivated, the landraces collected and those considered as lost, alongside with some information about their traditional uses. Finally, the importance of landraces in modern agriculture and preservation policies in Lemnos are discussed.     

Nitrogen fertilization effects on foliar nutrient dynamics and autumnal resorption in maidenhair tree (Gingko biloba L.)

We quantified seasonal foliar nutrient dynamics and autumnal N and P resorption of individuals of the deciduous gymnosperm Gingko biloba (maidenhair tree) growing in compacted, urban soils over two years following a single fertilization with 150 kg/ha/yr of N (and no P). Mean foliar nutrient concentrations were more similar to those reported for angiosperm trees than for other gymnosperms. During the autumn following fertilization, 46% and 48 of foliar N and P were resorbed, respectively; during the second year both increased significantly, to 68% of foliar N and 74% of foliar P. Absolute N resorption was also greater during the second year, whereas absolute P resorption did not differ significantly between years. During the second year, the level of N resorption rates was similar to that reported for Larix laricina (larch or tamarack), a needle‐leafed, deciduous gymnosperm, and greater than those reported for broad‐leafed deciduous angiosperms. The level of 1992 P resorption was similar to those reported for a wide range of gymnosperms and greater than those reported for most angiosperms. N fertilization allowed Gingko trees to maintain typical foliar N dynamics even during a persistent drought during which foliar P dynamics were significantly altered.     

Quantitative resistance to Botrytis cinerea from Solanum neorickii

Tomato (Solanum lycopersicum) is susceptible to gray mold (Botrytis cinerea). Quantitative resistance to B. cinerea was previously identified in a wild relative, S. neorickii G1.1601. The 122 F₃ families derived from a cross between the susceptible S. lycopersicum cv. Moneymaker and the partially resistant S. neorickii G1.1601 were tested for susceptibility to B. cinerea using a stem bioassay. Three putative quantitative trait loci (pQTL) were detected: pQTL3 and pQTL9 reducing lesion growth (LG) and pQTL4 reducing disease incidence (DI). For each pQTL, a putative homologous locus was identified recently in another wild tomato relative, S. habrochaites LYC4. pQTL3 was confirmed by assessing disease resistance in BC₃S₁ and BC₃S₂ progenies of S. neorickii G1.1601. pQTL4 was not statistically confirmed but the presence of the S. neorickii resistance allele reduced DI in all three tested populations. The reduction in LG of pQTL9 was not confirmed but rather, this locus conferred a reduced DI, similar to observations in the QTL study using S. habrochaites. The results are discussed in relation to other disease resistance loci identified in studies with other wild tomato relatives.     

A correlation network approach to metabolic data analysis for tomato fruits

Network analysis of correlations between abundances of metabolites across tomato genotypes can help in unraveling the biological basis of organoleptic variation in tomato. We illustrate how to construct and interpret simple correlations networks using metabolic data collected on a diverse set of tomato genotypes. Various types of correlations are calculated and displayed in the form of networks. Interpretations on the basis of network analyses are compared to interpretations following principal components analysis.     

Optimal management of a flammable multi-stand forest for timber production and maintenance of nesting sites for wildlife

Decline of cavity-using wildlife species is a major forest management issue. One of the causes of this problem is the loss in cavity tree abundance, resulting from short rotation silviculture, stand-replacing disturbance events and timber harvesting in disturbed stands. Cavity tree availability cannot be guaranteed due to the stochastic nature of disturbance events. We developed a Markov model to predict future cavity tree availability under alternative tree felling and fire protection strategies using information on cavity tree dynamics and fire history. Stochastic dynamic programming was used to find a strategy that maximizes timber revenues less forest management costs, including the cost of an artificial nest-box program that must be implemented whenever cavity trees become critically scarce. The requirement to implement a nest-box program in such circumstances strongly influenced the optimal tree felling strategy and resulted in a higher probability of having cavity trees in the future. This reflected an increase in the retention of old growth forest and stands with fire-killed cavity trees as well as stands of younger trees to provide a future source of cavities. These results demonstrate the need to consider the costs of artificial habitat enhancement and the risk of future cavity tree scarcity in multiple-use forest management planning.     

The rapid and accurate determination of germ tube emergence site by Blumeria graminis conidia

The development of appressoria by germinating Blumeria graminis conidia depends on its germ tubes making contact with the host surface. Low angle, low temperature scanning electron microscopy showed that 80% or more of first-formed germ tubes of f. spp. hordei, tritici and avenae conidia emerged from close to the host leaf surface, and so made contact with it allowing them to become functional primary germ tubes. Light microscopy of f. sp.hordei confirmed this result and, in addition, showed that germ tubes frequently emerged close to, and contacted, various hydrophobic and hydrophilic artificial substrata. Geometric models of conidium-substratum interfaces were developed and a “surface point method” was derived to predict the frequency with which contact would result if germ tube emergence was a random phenomenon. However, observed contact frequencies were far higher (c. three to eight times) than predicted. Thus, the germ tube emergence site was determined as a response to substratum contact. In part, this appeared to be a non-specific response. Nevertheless, germ tube contact frequencies were greater on the curved surface of leaf epidermal cells than on planar surface, suggesting that specific recognition of leaf surface characteristics may promote directional emergence. The area of contact required to stimulate directional germ tube emergence was very small: contact with a microneedle tip or with a spiders’ suspension thread was sufficient for many conidia. Similarly, on leaves, the only contact is between the tips of a limited number of conidial wall projections and the edges of epicuticular leaf wax plates. Micromanipulation to roll conidia so that their original site of contact with a leaf was rotated away from it, led to the majority of first-formed germ tubes growing away from the leaf, i.e. emerging close to the site of original contact. The experiments indicated that the site of germ tube emergence is determined within 1 min of deposition. This implicated the release of conidial extracellular materials in recognition of the conidium-leaf surface contact site.     

Detection and determination of p-coumaroylated units in lignins.

The derivatization followed by reductive cleavage (DFRC) method cleaves alpha- and beta-ethers in lignins but leaves lignin gamma-esters intact. When applied to grasses, which contain p-coumarate esters on their lignins, esterified monolignol derivatives are released. Saturation of the p-coumarate double bond occurs during DFRC, so the released products are 4-acetoxycinnamyl 4-acetoxyphenylpropionates. Synthesis of the esters allowed determination of response factors for the released products. Maize and bamboo lignins released 221 and 38 micromol/g of p-coumarate-derived esters. The sinapyl ester was much more abundant than the coniferyl one. The bamboo and maize lignin S/G ratios in the conjugates were 12 and 38 times greater than those of the normal monomers released by DFRC, evidence of a strong selectivity for acylation of syringyl units. Of three possible biochemical mechanisms for incorporating p-coumarates into lignin, evidence is mounting that the process involves incorporation of preacylated monolignols into the normal lignification process.