Genetic diversity assessments of brown rot pathogen Monilinia fructicola based on the six simple sequence repeat loci

Journal of Plant Diseases and Protection - Monilinia fructicola, causal agent of brown rot of stone fruits, is an economically important problem worldwide. Six of the sequence tagged microsatellite...     

Spatio-temporal patterns of pre-harvest brown rot epidemics within individual peach tree canopies

Tree canopies are architecturally complex and pose several challenges for measuring and characterizing spatial patterns of disease. Recently developed methods for fine-scale canopy mapping and three-dimensional spatial pattern analysis were applied in a 3-year study to characterize spatio-temporal development of pre-harvest brown rot of peach, caused by Monilinia fructicola, in 13 trees of different maturity classes. We observed a negative correlation between an index of disease aggregation and disease incidence in the same tree (r?=??0.653, P?<?0.0001), showing that trees with higher brown rot incidence had lower aggregation of affected fruit in their canopies. Significant (P?≤?0.05) within-canopy aggregation among symptomatic fruit was most pronounced for early-maturing cultivars and/or early in the epidemic. This is consistent with the notion of a greater importance of localized, within-tree sources of inoculum at the beginning of the epidemic. Four of five trees having >10 blossom blight symptoms per tree showed a significant positive spatial association of pre-harvest fruit rot to blossom blight within the same canopy. Spatial association analyses further revealed one of two outcomes for the association of new fruit rot symptoms with previous fruit rot symptoms in the same tree, whereby the relationship was either not significant or exhibited a significant negative association. In the latter scenario, the newly diseased fruit were farther apart from previously symptomatic fruit than expected by random chance. This unexpected result could have been due to uneven fruit ripening in different sectors of the canopy, which could have affected the timing of symptom development and thus led to negative spatial associations among symptoms developing over time in a tree.     

Studying neural organization in Aplysia with the scanning electron microscope

Preliminary attempts have been made to employ the scanning electron microscope in the mapping of a simple nervous system, the abdominal ganglion of Aplysia californica. Early results are encouraging: neuronal fibers have been identified and traced over relatively long distances from their cell bodies to structures tentatively identified as synapses and to structures tentatively identified as electrotonic connections.     

Disomic inheritance of anthocyanins and flavonol glycosides in the Tetraploid tuber-bearing speciesSolanum stoloniferum

Ten clones ofSolanum stoloniferum Schlechted (2n — 4x — 48) were selected from seedling populations that were produced by self-pollinating five introductions from the Commonwealth Potato Collection. These clones were used to produce S₁, F₁, F₂, and testcross populations. Clones and their progeny were scored for anthocyanins and flavonol glycosides in their corollas, stems, and leaves. Thin-layer chromatography (TLC) was used to separate and identify polyphenol compounds. No segregation for eight traits was observed within S₁ and F₁ families. Segregation was observed in F₂ and testcross populations for anthocyanins (derivatives of delphinidin and cyanidin, inhibited when the geneF is homozygous recessive); and flavonol glycosides (Q4 = quercetin 3-glucosyl-rhamnosylglucoside, controlled by the geneG1; and L1 = luteolin 7-glucoside, controlled by the geneL1) extracted from corollas. Observed ratios fitted ratios expected for disomic inheritance, differed from expected tetrasomic ratios, and provided additional evidence that the parental clones are homozygous. GenesF, G1, andL1 were genetically independent in dihybrid and trihybrid F₂ crosses.