Molecular and Morphological Characterization of Colletotrichum Species in the Colletotrichum gloeosporioides Complex Associated with Persimmon Anthracnose in South Korea.

Anthracnose is a major disease of persimmon in the pre- and postharvest phase. Several species of Colletotrichum (Colletotrichum gloeosporioides, C. acutatum, and C. horii) have been reported as causal agents of persimmon anthracnose in South Korea. In this study, a collection of 50 isolates associated with persimmon anthracnose were collected from Sangju (n = 25) and Cheongdo-gun (n = 25), South Korea. The morphological characteristics of all 50 Colletotrichum isolates were similar, and it was difficult to identify the isolates to the species level. A subsample of eight isolates was characterized phylogenetically to ascertain species. BLAST search and phylogenetic analysis of the internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and actin (ACT) genes revealed two species: C. horii as well as a previously unreported persimmon anthracnose causal agent C. siamense. C. siamense isolates were confirmed again by phylogenetic analysis of the ITS, ACT, GAPDH, calmodulin, and Apn2-Mat1-2 intergenic spacer partial mating type genes. Koch's postulates for C. horii and C. siamense were fulfilled, confirming the pathogenicity of the two species in persimmon fruit. Morphological characteristics (colony morphology and size and shape of conidia and appressoria) from two representative isolates support results of the phylogenetic analysis and match those of previous descriptions of C. horii and C. siamense.

Trichome density of main stem is tightly linked to PepMoV resistance in chili pepper (Capsicum annuum L.).

A relationship between pepper trichome and pepper mottle virus (PepMoV) resistance was examined. In an intraspecific F(2) mapping population from the cross between Capsicum annuum CM334 (trichome-bearing and PepMoV resistant) and Chilsungcho (glabrous and PepMoV susceptible), major QTLs for both traits were identified by composite interval mapping in linkage group (LG) 24 corresponding a telomere region on pepper chromosome 10. Ptel1 of putative trichome enhancing locus was a common major QTL for trichome density on the main stem and calyx. Ptel1 apart from HpmsE031 at a 1.03 cM interval was specifically associated to the trichome density on the main stem, whereas Ptel2 near m104 marker on LG2 was specific for the calyx trichome. Epistatic analysis indicated that Ptel1 engaged in controlling the trichome density by mutual interactions with the organ-specific QTLs. For PepMoV resistance, two QTLs (Pep1 and Pep2) were identified on the LG 24. Pep1 was located with Ptel1 in the R-gene cluster (RGC) for potyvirus resistance including Pvr4 with broad spectrum resistance to potyviruses. Pep1 flanking TG420 marker seemed to be the major factors determining correlation with PepMoV resistance. These results indicate that the level of trichome density on pepper main stem can be used as a morphological marker for Pvr4 in pepper breeding.

Improvement of antigen blotting in a tissue blot immunobinding assay for the detection of two chili pepper viruses.

The tissue blot immunobinding assay (TBIA) is widely used for the detection and localization of plant viruses in various plant tissues. The basic experimental procedures of TBIA sampling and blotting were simplified using commercially available micropipette tips. This method was termed the ring-blot immunobinding assay (R-BIA), as the blot on the membrane forms a ring shape. The detection efficacy of R-BIA was tested for two chili pepper viruses, pepper mild mottle tobamovirus (PMMoV) and pepper mottle potyvirus (PepMoV), following the optimized serological procedures of TBIA (length of the incubation period and BSA concentration, and primary and secondary antibodies). Sensitivity of the R-BIA was about 1 ng/ml of purified PMMoV in pepper leaf sap from a healthy pepper plant. R-BIA also showed high specificity in the detection of PMMoV and PepMoV. Moreover, the modified sampling and blotting procedures were simpler and more reliable than other TBIA methods (such as whole-leaf blotting and crushed-leaf blotting), suggesting that the R-BIA may be used for medium- to large-scale detection of plant viruses in laboratories with minimal facilities.