Meloidogyne aegracyperi n. sp. (Nematoda: Meloidogynidae), a root-knot nematode parasitizing yellow and purple nutsedge in New Mexico.

Meloidogyne aegracyperi n. sp. is described from roots of purple nutsedge in southern New Mexico, USA. Mature females are small (310-460 µm), pearly white, with their egg masses completely contained inside root galls. The neck is often at a 90 to 130° angle to the protruding posterior end with the perineal pattern. The distance of the dorsal esophageal gland orifice (DGO) to the base of the stylet is relatively long (4.0-6.1 µm), and the excretory pore is level with the base of the stylet. The anterior portion of the rounded lumen lining of the metacorpus contains 3 to 10 small vesicles. The perineal pattern has a rounded dorsal arch with a tail terminal area that is smooth or marked with rope-like striae. Only two males were found. The body twists 90° throughout its length. The DGO to the base of the stylet is long (3.0-3.3) µm. The cephalic framework of the second-stage juvenile is weak, and the stylet is short (10.1-11.8 µm). The DGO to the base of the stylet is long (3-5 µm). The tail is very long (64-89 µm) and the hyaline portion of the tail is very narrow, making the tail finely pointed. Eggs are typical for the genus and vary in length (85.2-99.8 µm) and width (37.1-48.1 µm), having a L/W ratio of (2.1-2.6). Maximum likelihood phylogenetic analyses of the different molecular loci (partial 18S rRNA, D2-D3 of 28S rRNA, internal transcribed spacer (ITS) rRNA, cytochrome oxidase subunit II (COII)-16S rRNA of mitochondrial DNA gene fragments and partial Hsp90 gene) placed this nematode on an independent branch in between M. graminicola and M. naasi and a cluster of species containing M. chitwoodi. M. fallax, and M. minor. Greenhouse tests showed that yellow and purple nutsedge were the best hosts, but perennial ryegrass, wheat, bentgrass, and barley were also hosts.

New Mexico and the southwestern US are affected by a unique population of tomato spotted wilt virus (TSWV) strains.

Tomato spotted wilt virus (TSWV) is an important pathogen of many ornamental, greenhouse and agronomic crops worldwide. TSWV also causes sporadic problems in a number of crops in New Mexico (NM). Nucleocapsid gene sequences obtained from six different crop species across the state over four different years were used to characterize the NM TSWV population. This analysis shows that NM is affected by a unique TSWV population that is part of larger independent population present in the southwestern US. This population likely arose due to geographic isolation and is related to other TSWV populations from the US, Spain, and Italy.

First Report of Xylella fastidiosa in Peach in New Mexico.

Xylella fastidiosa is a gram-negative bacterium that causes disease in a wide variety of plants such as grapes, citrus trees, oleanders, and elm and coffee trees. This bacterium is xylem limited and causes disease symptoms such as leaf scorch, stunting of plant growth, branch dieback, and fruit loss. The presence of X. fastidiosa was previously reported in New Mexico where it was found to be infecting chitalpa plants and grapevines (3). In the summer of 2010, peach (Prunus persica (L.) Batsch) trees from two locations in northern New Mexico exhibited leaf deformity and stunting, dark green venation, slight mottling, and branch dieback. Preliminary viral diagnostic screening was performed by Agdia (Elkhart, IN) on one symptomatic tree and it was negative for all viruses tested. Three trees from two different orchards tested positive for X. fastidiosa by ELISA and PCR analysis using X. fastidiosa-specific primer sets HL (1) and RST (2). Bacterial colonies were also cultured from these samples onto periwinkle wilt media. Eight colonies obtained from these three plants tested PCR positive using the X. fastidiosa-specific primers. The 16S ribosomal and 16S-23S rRNA internal transcribed spacer (ITS) region (557 nucleotides) (GenBank Accession No. HQ292776) along with the gyrase region (400 nucleotides) (GenBank Accession No. HQ292777) was amplified from the peach total DNA samples and the bacterial colonies. Sequencing analysis of these regions indicate that the X. fastidiosa found in peach is 100% similar to other X. fastidiosa multiplex isolates including isolates from peach, pecan, sycamore, and plum trees and 99% similar to the X. fastidiosa isolates previously found in New Mexico. Further analysis of the 16S ribosomal and 16S-23S rRNA ITS sequences with maximum likelihood phylogenetic analysis using Paup also groups the peach isolates into the X. fastidiosa multiplex subspecies. The gyrase sequence could not be used to differentiate the peach isolates into a subspecies grouping because of the lack of variability within the sequence. This X. fastidiosa multiplex subspecies could possibly be a threat to the New Mexico pecan industry since pecan infecting X. fastidiosa isolates belong to the same bacterial subspecies. It is not known if X. fastidiosa subspecies multiplex isolates from peach are capable of infecting pecans but they are closely genetically related. It is interesting to note that the isolates from peach are different than previously described X. fastidiosa isolates in New Mexico that were infecting chitalpa and grapes (3). X. fastidiosa has previously been described in peach; the disease is called "phony peach". The peach trees exhibited stunting and shortened internodes as reported for "phony peach". They also exhibited slight mottling and branch dieback that may be due to the environment in New Mexico or perhaps they are also exhibiting mineral deficiency symptoms in association with the X. fastidiosa disease. To our knowledge, this is the first report of X. fastidiosa in peach in New Mexico. References: (1) M. H. Francis et al. Eur. J. Plant Pathol. 115:203, 2006. (2) G. V. Minsavage et al. Phytopathology 84:456, 1994. (3) J. J. Randall et al. Appl. Environ. Microbiol. 75:5631, 2009.

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.

Xylella fastidiosa Detected in New Mexico in Chitalpa, a Common Landscape Ornamental Plant.

Different strains of Xylella fastidiosa cause a variety of significant disease problems in agricultural and ornamental plants, including Pierce's disease in grapes, oleander leaf scorch, pecan bacterial leaf scorch, and alfalfa dwarf disease. X. fastidiosa has never been reported in New Mexico but is known to exist in surrounding states (California, Arizona, and Texas). During the summer of 2006, several chitalpa (Chitalpa tashkinensis) hybrid trees with leaf scorch symptoms and branch die back were observed in Las Cruces, NM and they tested positive for X. fastidiosa by ELISA. Additional samples from these plants and others were analyzed by ELISA, PCR (2), and cultured on XfD2 medium (1). Known positive and negative oleander samples from Arizona were included as controls. Fifteen of thirty tested chitalpa were PCR and ELISA positive, indicating that they were infected with X. fastidiosa. Bacterial colonies that were PCR positive were also recovered from 10 of the XF positive samples that were plated. DNA sequences of PCR products amplified from chitalpa and isolated bacterial colonies (GenBank Accession Nos. EF109936 and EF109937) were identical to each other, 97% similar to X. fastidiosa strain JB-USNA, and 96% similar to the Temecula 1 strain. Independent ELISA testing (Barry Hill, California Department Food and Agriculture, Sacramento, CA) confirmed our ELISA and PCR results. On the basis of these results, we conclude that X. fastidiosa is present in New Mexico and that the common landscape ornamental chitalpa is a host for X. fastidiosa. Additional work is required to determine if X. fastidiosa is pathogenic to chitalpa and to examine the relevance of this potential X. fastidiosa reservoir to agricultural production in New Mexico and other areas where chitalpa is grown. References: (1) R. P. P. Almeida et al. Curr. Microbiol. 48:368, 2004. (2) M. R. Pooler et al. Lett. Appl. Microbiol. 25:123, 1997.