First Report of Sour Rot of California Peaches and Nectarines Caused by Yeasts.

In early July 2001, samples of nectarine and peach fruit were brought from orchards in northern Tulare County or from packinghouses to our laboratory for diagnosis of an unusual decay. When the decay lesions originated close to the stylar end, leaking juice streamed from it. When the decay lesion was on the stem end of the fruit and touched the packing box, it developed a decay consisting of a ring of 0.5 to 2.0 cm (inner diameter) and 1.0 to 3.0 cm (outer diameter). The leaking juice dissolved the cuticle, epidermis, and some of the flesh, creating distinct furrows in the tissue. Samples with similar decay lesions were examined in 2001, 2002, and 2003. In each year, isolations from these fruit consistently yielded two or three different yeasts that were identified as Geotrichum candidum Link, Issatchenkia scutulata (Phaff et al.) Kurtzman et al., and Kloeckera apiculata (Reess emend. Klocker) Janke. All three yeasts were isolated from most of the samples, although sometimes, different combinations of two of the yeasts recovered. To complete Koch's postulates, each yeast was single spored and cultured on acidified potato dextrose agar at 25°C to prepare a dense (108) cell suspension. Eight, mature, 'Elegant Lady' peach fruit were surface disinfested in 0.1% sodium hypochlorite for 3 min, allowed to dry, and wounded once with a sterile nail (3 × 5 mm) on the fruit cheek. A 50-µl drop of the cell suspension was placed in each wound, and the peaches were incubated in containers with >95% relative humidity at 27°C. Fruit inoculated similarly with a 50-µl drop of sterile water served as controls. In 2001, two containers containing eight fruit each were used for each yeast, and lesions started developing within 1 week after inoculation. The diameter of the decay lesion was measured after 10 days of incubation of the fruit. The diameter of decay lesions ranged from 21 to 68 mm for G. candidum, 30 to 55 mm for I. scutulata, and 9 to 39 mm for K. apiculata inoculations. The inoculation experiment was repeated with two containers of eight 'Red Glo' nectarine fruit per treatment yeast, under the same conditions as described above. Organisms recovered from the decay lesions were the same yeasts used for inoculating the peaches or nectarines. All three yeasts caused similar decay lesions in peaches, and the leaking effect was reproduced in both types of fruit. Symptoms were similar to those observed on fruit samples brought to our laboratory. Control fruit did not develop the characteristic decay lesions, although brown rot caused by Monilinia fructicola developed on a few of the control fruit. We concluded that each isolated yeast had the capacity to cause sour rot decay on stone fruit. From samples and reports, the disease has been found on 'Red Glo', 'Ruby Diamond', 'Zee Grand', 'Spring Bright', and 'Honey Blaze' nectarines and 'Elegant Lady' and 'Fire Red' peaches. G. candidum was isolated from peaches and other fruit in California and incited rot of 'Paloro' peach in 1960 (2) and caused postharvest sour rot of peaches originating from Georgia, Pennsylvania, New Jersey, and North Carolina (1). However, to our knowledge, this is the first report of G. candidum, I. scutulata, or K. apiculata causing sour rot of commercial peaches and nectarines in the field and postharvest situations in California. References: (1) C. L. Burton and W. R. Wright. Plant Dis. Rep. 53:580, 1969. (2) E. E. Butler. Phytopathology 50:665, 1960.

Distribution of leaf mass per unit area and leaf nitrogen concentration determine partitioning of leaf nitrogen within tree canopies.

Distribution of leaf nitrogen with respect to leaf mass per unit area (M(a)), nitrogen per unit mass (N(m)) and nitrogen per unit area (N(a)) within peach (Prunus persica L.) tree canopies was studied in two field experiments. In one experiment, leaf light exposure and M(a) were measured on leaves from different canopy positions of peach trees subjected to five nitrogen (N) fertilization treatments. Leaf light exposure and M(a) were linearly related and the relationship was independent of N fertilization. In a subsequent experiment, N fertilizer was applied to previously unfertilized trees in midsummer, after shoot growth had terminated. Application of N fertilizer did not affect mean canopy M(a). Fertilization increased N(m) of all leaves throughout the canopy compared with non-fertilized trees. No significant relationship between N(m) and M(a) was found in either fertilized or control trees. There was a linear relationship between N(a) and M(a) and the slope of the relationship was increased by N fertilizer application. We conclude that distribution of N(a) in peach tree canopies is primarily a function of M(a) partitioning with light and N(m), which is related to soil N availability.

Human alpha-L-iduronidase (IDUA) gene: apparent recombination in intron 2 by haplotype analysis in a Taiwanese population.

The polymorphic DNA haplotype of the alpha-L-iduronidase (IDUA) gene in a Taiwanese population was investigated. Genomic DNA extracted from 85 volunteers was used to amplify fragments containing the polymorphic sites A8, A20 and Q33H from exon 1 and a variable number of tandem repeats (VNTR) region in intron 2. Additionally, sites R105Q and L118 in exon 3, A314 from exon 7, A361T and T388 from exon 8, T410 and V454I from exon 9, and R489 from exon 10 were amplified. The polymerase chain reaction-amplified products were analyzed by restriction fragment length polymorphism (RFLP) analysis, allele specific oligonucleotide (ASO) hybridization, or gel electrophoresis. Of the examined polymorphisms, the intron 2 VNTR was not in Hardy-Weinberg equilibrium. Conversely, all 11 single base change polymorphisms were in Handy-Weinberg equilibrium. Linkage disequilibrium analysis of the haplotype data revealed strong nonrandom association between A8 and A20 in exon 1 as well as among R105Q, A314, A361T, T388, T410, V454I, and R489 in exons 3 to 10. In contrast, little linkage disequilibrium between two clusters of linked polymorphisms on either side of the VNTR was observed. The results suggest apparent recombination in intron 2 of the IDUA gene, with little or no recombination in exon 1 or exons 3 to 10.

Human alpha-L-iduronidase (IDUA) gene: correlation of polymorphic DNA haplotype and IDUA activity in Chinese population.

The correlation of polymorphic DNA haplotype of the alpha-L-iduronidase (IDUA) gene and IDUA activity in Chinese subjects was investigated. Genomic DNA extracted from 85 randomly sampled normal individuals was used to amplify fragments containing the polymorphic change site A8, Q33H (exon 1), R105Q (exon 3), A361T (exon 8), or V454I (exon 9). The PCR amplified products were analyzed by means of restriction fragment length polymorphism (RFLP) or allele specific oligonucleotide (ASO) hybridization. Leukocytes were isolated from the above 85 samples, and their IDUA activities were determined. A wide range of IDUA activity (50-300 nmol/h/mg cell protein) with an average of 156 nmol/h/mg cell protein was observed. When the allele frequency was compared between individuals with IDUA activity below 90% or above 110% of the average, a bias toward the common allele "1" of Q33H (Gln33) was detected in individuals with higher IDUA activity. Conversely, the polymorphic allele "2" of R105Q (Gln105), A361T (Thr361), and V454I (Ile454) was found in the higher IDUA activity group. Linkage disequilibrium analysis of the haplotype data revealed strong nonrandom association among the polymorphic alleles of R105Q, A361T, and V454I. Of the haplotypes constructed by Q33H, R105Q, A361T, and V454I, a positive correlation between haplotype 1,2,2,2 (Gln33, Gln105, Thr361, Ile454) and IDUA activity was observed. The IDUA activity was found to increase with Gln105, Thr361, or Ile454 polymorphic changes by mutagenesis and expression of IDUA cDNA in COS-7 cells. By combining the positive effect of Gln105, Thr361, and Ile454 in one cDNA construct, it may be possible to produce a high activity IDUA protein for MPS I enzyme replacement therapy.