Influence of water stresses on capsaicinoid production in hot pepper (Capsicum chinense Jacq.) cultivars with different pungency levels.

Although water stress reduces fruit yield, it also increases capsaicinoid accumulation in hot pepper. The aim of this study was to investigate the effect of different water regimes on capsaicinoid production in Capsicum chinense Jacq. having different pungency levels. Four hot pepper (C. chinense) cultivars were planted with four water regimes after anthesis: daily irrigation (control; S1), every 2 days (S2), every 3 days (S3) and every 4 days (S4). The results found that Akanee Pirote with the S2 treatment gave the highest capsaicinoid yield, and the increase of capsaicinoid yield was attributed from increasing the absolute capsaicinoid content and reducing the dry fruit yield as compared to the control. Capsaicinoid yield of Bhut Jolokia, Orange Habanero, and BGH1719 responded to the water stresses, but produced less capsaicinoid yield as compared to the control. This study reveals that appropriate water stress could increase capsaicinoid yield in some, but not all, hot pepper cultivars.

Characterizing and marker-assisting a novel chili pepper (Capsicum annuum L.) yellow bud mutant with cytoplasmic male sterility.

Cytoplasmic male sterility (CMS) in pepper is a better way to produce hybrid seeds compared to manual production. We used the two sequence characterized amplified region (SCAR) markers (CRF-SCAR and CMS-SCAR130) in CMS pepper, to identify the genotype. We assembled two CMS yellow bud mutants (YBM; YBM12-A and YBM12-B). This mutation in leaf color is controlled by a single dominant nuclear gene. The aim was to create a new hybrid seed production method that reduces the costs and increases F1 hybrid seed purity. The results suggest that the CRF-SCAR and CMS-SCAR130 markers can be used together in multiple generations to screen for restorer or maintainer genes. We found the marker linked to the restorer gene (Rf) in the C-line and F1 hybrids, as well as partially in the F2 generation, whereas it was not found in the sterile YBM12-A or the maintainer line YBM12-B. In the F2 population, sterility and fertility segregated at a 3:1 ratio based on the CRF-SCAR marker. A 130 bp fragment was produced in the YBM12-A, F1, and F2 populations, suggesting that these lines contained sterile cytoplasm. A 140 bp fragment present in the YBM12-B and C-line indicated that these lines contained normal cytoplasm. In addition, we identified some morphological characters distinguishing sterile and fertile buds and flowers that may be linked to the sterility gene. If more restorer lines are identified, CMS expressing the YBM trait can be used in hybrid seed production.

Brote Grande, a New Phytoplasma-Associated Disease of Chile Peppers.

Chile is one of the most important crops in New Mexico, contributing both to the agricultural economy and cultural identity of the state. Chile producers in New Mexico and Arizona have reported a disorder of unknown etiology that has increased in frequency for the past several years. Affected plants have a bushy appearance, develop overly large green calyces instead of normal flowers, and fail to set fruit. This characteristic phyllody is similar to symptoms associated with other phytoplasma-caused diseases, such as tomato big bud, and has led chile producers to refer to the disorder as "brote grande", which is Spanish for "big bud". PCR analysis using the phytoplasma-specific primer pairs P1/Tint and P1/P7 (4) produced amplicons of the expected size (~1.6 kb) from symptomatic but not healthy samples. Direct sequencing of the P1/P7 PCR amplicons determined that they contained the expected 16S rRNA and internal transcribed spacer (ITS) sequences and included the tRNAIle typically found in phytoplasma ITS regions. BLAST analysis of the brote grande sequence (GenBank Accession No. FJ525437) indicated it is most closely related (99% identity) to sequences reported for previously characterized 16Sr group VI phytoplasmas, such as 'Candidatus Phytoplasma trifolii' (Accession No. AY390261) and the Vinca virescence (Accession No. AY500817) phytoplasma. 'Candidatus phytoplasma trifolii' is synonymous with beet leafhopper virescence, which was reported as a cause of tomato big bud in California during the mid 1990s (3). The brote grande phytoplasma was less related to other phytoplasmas known to affect peppers such as the 16Sr group XII stolbur of pepper phytoplasma (Accession No. AF248959) and newly described 16Sr group I phytoplasmas described in peppers in Cuba (Accession No. DQ286947) and Mexico (Accession No. DQ092321) (1,2). The brote grande phytoplasma is also distinct from other phytoplasmas, such as potato purple top and tomato little leaf that are common in Mexico, affecting solanaceous crops in the region (2). Although the disease frequency never exceeded 5% in any given field, plants displaying brote grande symptoms were observed in the majority of chile pepper fields examined from July to September of 2008. The presence of the brote grande associated phytoplasma was confirmed by PCR and sequence analysis of symptomatic plants from 10 different fields ranging from Las Cruces, NM to Tucson, AZ, indicating that brote grande disease is widespread across the major chile-producing areas of the Desert Southwest. The brote grande phytoplasma sequence was the only phytoplasma sequence detected in any of the symptomatic chile samples. Taken together, the etiology, PCR, and DNA sequence results all indicate that brote grande of chile is a new disease of chile peppers associated with infection by a novel 16Sr group VI phytoplasma and that this disease is distributed across the major chile-producing areas of the Desert Southwest. References: (1) Y. Arocha. Plant Pathol. 56:345, 2007. (2) M. E. Santos-Cervantes et al. Plant Dis. 92:1007, 2008. (3) M. E. Shaw et al. Plant Dis. 77:290, 1993. (4) C. D. Smart et al. Appl. Environ. Microbiol. 62:2988, 1996.

Recombinant inbred line differential identifies race-specific resistance to phytophthora root rot in Capsicum annuum.

A differential series is the normal method for identification of races within a plant pathogen and a host interaction. A host differential is extremely useful for phytopathological as well as breeding purposes. A set of recombinant inbred lines (RILs) were developed and characterized for race differentiation of Phytophthora root rot caused by Phytophthora capsici. The highly resistant Capsicum annuum accession Criollo de Morelos-334 was hybridized to a susceptible cultivar, Early Jalapeno, to generate the RIL population. The host differential characterized 17 isolates of P. capsici into 13 races. The establishment of a stable host differential for the P. capsici and C. annuum interaction will assist researchers in understanding the complex inheritance of resistance to Phytophthora root rot and to develop resistant cultivars.

Inheritance of seed color in Capsicum.

The mode of seed color inheritance in Capsicum was studied via an interspecific hybridization between C. pubescens Ruiz and Pav. (black seed color) and C. eximium Hunz. (yellow seed color). Black seed color was dominant over yellow seed color. The F(2) segregation pattern showed continuous variation. The generation means analysis indicated the presence of a significant effect of additive [d], dominance [h], and additive x additive [i] interaction for seed color inheritance. The estimate for a minimum number of effective factors (genes) involved in seed color inheritance was approximately 3.

Inheritance of a novel flaccid mutant in Capsicum annuum.

A mutant that causes a novel flaccidity phenotype in bell pepper (Capsicum annuum L.) was generated by treating seeds with ethyl methanesulfonate (EMS). Inheritance studies indicated that the mutant was controlled by a single recessive gene. It is proposed that the gene designation representing this mutation be flc (flaccid). The mutation may be useful for investigations of the genetic basis for turgor maintenance and drought stress physiology.

Inheritance of unique fruit and foliage color mutation in NuMex piñata.

The inheritance of mature fruit color in peppers (Capsicum spp.) is controlled by several genes. However, the inheritance of the transition of colors the fruit undergo during ripening has not been described extensively. The authors describe the inheritance of a unique gene which affects foliage color and fruit color transition occurring in the jalapeño cultivar NuMex Piñata. The gene responsible is designated the tra gene.