First Report of Pestalotiopsis trachicarpicola Causing Leaf Blight on Panax notoginseng in China.

Panax notoginseng (Burkill) F. H. Chen ex C. Y. Wu & K.M. Feng is a Chinese herbal medicinal plant for treating diseases of the central nervous system and cardiovascular system, widely used as a medicine and health-care product. In May 2022, leaf blight disease was found on leaves of 1-year-old P. notoginseng in the plantings （27.904°N, 112.918°E） of Xiangtan City (Hunan) with an area of 104 m2. Over 400 plants were investigated, up to 25% of the plants were symptomatic. From the margin of the leaf, the initial symptoms of water-soaked chlorosis and following dry yellow with slight shrinkage appeared. Later, leaf shrinkage became serious and chlorosis enlarged gradually, leading to leaf death and abscission. To identify the causal agent, 20 leaf lesions (4 mm2) collected from 20 individual 1-year-old plants were sterilized with 75% ethanol for 10 s, 5% NaOCl for 10 s, rinsed in sterilized water three times, placed on potato dextrose agar (PDA) with lactic acid (0.125%) for inhibition the growth of bacteria, and incubated at 28°C for 7 days (Fang, 1998). Five isolates were obtained from 20 leaf lesions of different plants with the isolation rate of 25% and purified by single sporing, which have similar colony and conidia morphology characteristics. One isolate PB2-a was selected randomly for further identification. Colonies of PB2-a on PDA were white with cottony mycelium, developing concentric circles (top view) or light yellow (back view). Conidia (23.1 ± 2.1 × 5.7 ± 0.8 µm, n=30)were fusiform, straight or slightly curved and contained conic basal cell, three light brown median cells and hyaline conic apical cell with appendages. The rDNA internal transcribed spacer (ITS), the translation elongation factor 1-alpha (tef1), and the ß-tubulin (TUB2) genes were amplified from genomic DNA of PB2-a using primers ITS4/ITS5 (White et al. 1990), EF1-526F/EF1-1567R (Maharachchikumbura et al. 2012), and Bt2a/Bt2b (Glass and Donaldson, 1995; O'Donnell and Cigelnik, 1997), respectively. BLAST search of sequenced ITS (OP615100), tef1 (OP681464) and TUB2 (OP681465) exhibited > 99% identity with the type strain of Pestalotiopsis trachicarpicola OP068 (JQ845947, JQ845946 and JQ845945). Phylogenetic tree of the concatenated sequences was constructed based on the maximum-likelihood method using MEGA-X. Isolate PB2-a was identified as P. trachicarpicola based on morphological and molecular data (Maharachchikumbura et al. 2011; Qi et al. 2022). PB2-a was tested for pathogenicity three times to confirm Koch's postulates. Twenty healthy leaves on 20 1-year-old plants were punctured with sterile needles and inoculated with 50 µl of conidial suspension (1×106 conidia/ml). The controls were inoculated with sterile water. All plants were placed in a greenhouse at 25°C under 80% relative humidity. After 7 days, all inoculated leaves developed leaf blight symptoms identical to those described above, whereas the control plants kept healthy. P. trachicarpicola were reisolated from infected leaves, and identical to those of the originals based on the colony characteristics and the sequenced data of ITS, tef1 and TUB2. P. trachicarpicola was reported as a pathogen of leaf blight on Photinia fraseri (Xu et al. 2022). To our knowledge, this is the first report of P. trachicarpicola causing leaf blight on P. notoginseng in Hunan, China. Leaf blight is one of the destructive diseases in P. notoginseng production, identification of the pathogen will be useful to develop effective disease management and protect P. notoginseng, a medical plant with economic value.

Disaggregation of Ploidy, Gender, and Genotype Effects on Wood and Fiber Traits in a Diploid and Triploid Hybrid Poplar Family.

Triploid breeding based on unilateral sexual polyploidization is an effective approach for genetic improvement of Populus, which can integrate heterosis and ploidy vigor in an elite variety. However, the phenotypic divergence of unselected allotriploids with the same cross-combination remains poorly understood, and the contributions of ploidy, gender, and genotype effects on phenotypic variation are still unclear. In this study, wood and fiber traits, including basic density (BD), lignin content (LC), fiber length (FL), fiber width (FW), and fiber length/width (FL/W), were measured based on a 10-year-old clonal trial, including full-sib diploid and triploid hybrids of (Populus pseudo-simonii × P. nigra 'Zheyin3#') × P. × beijingensis, and contributions of ploidy, gender, and genotype effects on the variation of these traits, were disaggregated to enhance our understanding of triploid breeding. We found a significant phenotypic variation for all measured traits among genotypes. All the wood and fiber traits studied here underwent strong clonal responses with high repeatabilities (0.55-0.76). The Pearson's correlation analyses based on the best linear unbiased predictors (BLUPs) revealed that BD was significantly positively correlated with FL (r = 0.65, p = 0.030), suggesting that BD could be improved together with FL during triploid breeding. The FL of the triploids was significantly larger than that of the diploids (p < 0.001), suggesting that ploidy strongly affected the variation of FL traits. The difference between females and males was not significant for any measured trait, implying that gender might not be a major factor for variation in these traits. Further analyses of variance components showed that genotype dominantly contributed to the variation of BD, LC, and FW traits (with 54, 62, and 53% contributions, respectively) and ploidy contributed strongly to variation in FL and FL/W (77 and 50%, respectively). The genetic coefficient of variation (CVG) of triploids for each trait was low, suggesting that it is necessary to produce many triploids for selection or to use different Populus species as parents. Our findings provide new insights into the genetic effects of ploidy, gender, and genotype on wood and fiber traits within a full-sib poplar family, enhancing the understanding of the triploid breeding program of Populus.

Variation of Chromosome Composition in a Full-Sib Population Derived From 2x × 3x Interploidy Cross of Populus.

Interploidy cross commonly results in complex chromosome number and structural variations. In our previous study, a progeny with segregated ploidy levels was produced by an interploidy cross between diploid female parent Populus tomentosa × Populus bolleana clone TB03 and triploid male parent Populus alba × Populus berolinensis 'Yinzhong'. However, the chromosome compositions of aneuploid genotypes in the progeny were still unclear. In the present study, a microsatellite DNA allele counting-peak ratios (MAC-PR) method was employed to analyze allelic configurations of each genotype to clarify their chromosome compositions, while 45S rDNA fluorescence in situ hybridization (FISH) analysis was used to reveal the mechanism of chromosome number variation. Based on the MAC-PR analysis of 47 polymorphic simple sequence repeat (SSR) markers distributed across all 19 chromosomes of Populus, both chromosomal number and structural variations were detected for the progeny. In the progeny, 26 hypo-triploids, 1 hyper-triploid, 16 hypo-tetraploids, 10 tetraploids, and 5 hyper-tetraploids were found. A total of 13 putative structural variation events (duplications and/or deletions) were detected in 12 genotypes, involved in chromosomes 3, 6, 7, 14, 15, 16, and 18. The 46.2% (six events) structural variation events occurred on chromosome 6, suggesting that there probably is a chromosome breakpoint near the SSR loci of chromosome 6. Based on calculation of the allelic information, the transmission of paternal heterozygosity in the hypo-triploids, hyper-triploid, hypo-tetraploids, tetraploids, and hyper-tetraploids were 0.748, 0.887, 0.830, 0.833, and 0.836, respectively, indicating that the viable pollen gains of the male parent 'Yinzhong' were able to transmit high heterozygosity to progeny. Furthermore, 45S rDNA-FISH analysis showed that specific-chromosome segregation feature during meiosis and chromosome appointment in normal and fused daughter nuclei of telophase II of 'Yinzhong,' which explained that the formation of aneuploids and tetraploids in the progeny could be attributed to imbalanced meiotic chromosomal segregation and division restitution of 'Yinzhong,' The data of chromosomal composition and structural variation of each aneuploid in the full-sib progeny of TB03 × 'Yinzhong' lays a foundation for analyzing mechanisms of trait variation relying on chromosome or gene dosages in Populus.

[Gene characteristics and changing trend of neonatal thalassemia in Dongguan, China].

OBJECTIVE: To study the gene distribution characteristics of neonatal thalassemia in Dongguan, China and the changing trend of the gene distribution characteristics of neonates with thalassemia in Dongguan in 2014-2018. METHODS: A retrospective analysis was performed for the data on neonatal thalassemia screening from the Dongguan Neonatal Disease Screening System between January 2014 and December 2018. A total of 616 718 neonates were enrolled who were born in Dongguan. RESULTS: Among the 616 718 neonates, 52 308 were positive for primary screening, 10 366 were recalled, 8 576 underwent genetic diagnosis, and 6 432 were confirmed with thalassemia by genetic diagnosis. The carrying rates of thalassemia genes in 2014-2018 were 5.81%, 5.47%, 5.96%, 6.91%, and 7.90% respectively, and showed an upward trend (P<0.001). The positive rates of neonatal thalassemia screening in 2014-2018 were 9.12%, 8.34%, 7.54%, 8.13%, and 9.32% respectively (P<0.001). The positive rates of genetic diagnosis of neonatal thalassemia in 2014-2018 were 0.89%, 1.11%, 1.24%, 0.90%, and 1.09% respectively (P<0.001). In 2014-2018, 5 098 cases of α-thalassemia were detected, accounting for 79.26% of all cases, and 1 230 cases of ß-thalassemia were detected, accounting for 19.12% of all cases. The detection rate of α-thalassemia was significantly higher than that of ß-thalassemia in each year (P<0.001). In 2014-2018, static α-thalassemia, mild α-thalassemia, and mild ß-thalassemia were the main types observed in neonates. CONCLUSIONS: Most of the neonates with thalassemia have α-thalassemia in Dongguan, with static α-thalassemia and mild α-thalassemia as the main types. The carrying rate of thalassemia genes keeps increasing in neonates in Dongguan, and the prevention and treatment of thalassemia is still challenging.

Genetic screening involving 101 hot spots for neonates not passing newborn hearing screening and those random recruited in Dongguan.

In order to investigate essential molecular causes for hearing loss and mutation frequency of deafness-related genes, 1315 newborns who did not pass the Newborn Hearing Screening (NHS) (audio-no-pass) and 1000 random-selected infants were subjected to detection for 101 hotspot mutations in 18 common deafness-related genes. Totally, 23 alleles of 7 deafness genes were detected out. Significant difference (χ2 = 25.320, p = 0.000) existed in causative mutation frequency between audio-no-pass group (81/1315, 6.160%) and random-selected cohort (18/1000, 1.80%). Of the genes detected out, GJB2 gene mutation was with significant difference (χ2 = 75.132, p = 0.000) between audio-no-pass group (417/1315, 31.711%) and random-selected cohort (159/1000, 15.900%); c.109G > A was the most common allele, as well as the only one with significantly different allele frequency (χ2 = 79.327, p = 0.000) between audio-no-pass group (392/1315, 16.84%) and random-selected cohort (140/1000, 7.55%), which suggested c.109G > A mutation was critical for newborns' hearing loss. This study performed detection for such a large scale of deafness-associated genes and for the first time compared mutations between audio-no-pass and random-recruited neonates, which not only provided more reliable DNA diagnosis result for medical practioners and enhanced clinical care for the newborns, but gave more accurate estimation for mutation frequency.