Classification of wheat PPO genes and effect of non-synonymous cSNP on kernel PPO activity

Polyphenol oxidase (PPO) activity is highly related to the undesirable browning of wheat-based end products. In this study, wheat PPO sequences (mRNA) were searched/BLASTed in the NCBI database and aligned using DNAMAN software. The results showed that wheat PPO genes could be divided into two clusters (I and II) and that three genes (‘i’) of cluster II seemed not to be located on chromosomes 2A and 2D. Ninety-four single nucleotide polymorphisms (SNPs) were detected between two haplotypes of the PPO gene on chromosome 2D. Eighty of these were found in the coding region (coding (c) SNPs) and 36 were non-synonymous cSNPs, which could affect the PPO amino acid sequence. Primers (STS-H) were designed at some non-synonymous cSNPs sites and were used to investigate the correlations between allelic variants and PPO activity of seeds – a total of 130 common wheat varieties were evaluated in 2 years. The results showed that STS-H could amplify a 460 bp DNA fragment in most cultivars with high PPO activity, while no PCR product was detected in most cultivars with low PPO activity. To improve the selection efficiency of a single dominance molecular marker, the multiplex polymerase chain reaction (PCR) system of STS-H and STS01 markers was also studied, based on the complementary between them.

Occurrence of Tomato yellow leaf curl virus in Tomato in Martinique, Lesser Antilles

During April of 2002, symptoms of stunting and chlorotic curled leaves of reduced size, similar to those caused by Tomato yellow leaf curl virus (TYLCV), were observed for the first time in commercial tomato (Solanum lycopersicum) in the northwest region of Martinique. Six months later, many tomato fields had more than 80% of plants expressing these symptoms and yield was drastically reduced. Samples from two symptomatic plants were collected and analyzed by PCR. Primers PC1 (5′-TGACTATGTCGAAGCGACCAGG-3′) and PC2 (5′-CGACATTACAGCCTCAGACTGG-3′) were used to amplify a 950-bp fragment within the coat protein gene (CP) of TYLCV species (1). Primer pair MP16-MP82 (2) amplified a 550-bp fragment from the conserved nonanucleotide sequence (TAATATTAC) to the 5′ end of the CP gene. Products of expected sizes were obtained with both pairs of primers from symptomatic samples but not from uninfected ones. The two overlapping PCR products were cloned into a pGEM-T Easy Vector (Promega, Madison, WI) and sequenced. A BLAST analysis was conducted with begomovirus sequences available in the GenBank database at the NCBI, and DNAMAN software (Lynnon Corporation, Quebec, Canada) was used for further comparisons. The 1275-bp sequence (GenBank Accession No. EF490995) shared 99% nucleotide identity with the partial sequences of TYLCV from Antigua and Barbuda (GenBank Accession No. EF028240), Saint Kitts and Nevis (GenBank Accession No. EF028239), and the two overlapping sequences from Guadeloupe (GenBank Accessions No. AY319645 and AY319646). It was at least 98% identical to TYLCV isolates from Florida (GenBank Accession No AY530931), Dominican Republic (GenBank Accession No. AF024715), and Cuba (GenBank Accession No. AJ223505). These results confirm the introduction of TYLCV into Martinique, possibly from a nearby Caribbean country, and reveal its southward spread in the Lesser Antilles. The nearness of the islands in the Lesser Antilles (20 to 100 km distant) probably permitted the rapid spread of TYLCV through the movement of plant material or wind transport of viruliferous whiteflies from one island to the next. Monitoring the spread of TYLCV in this Caribbean archipelago is important for regional virus management and in forecasting the spread of TYLCV to nearby countries in South America. References: (1) Y. Martinez et al. Rev. Prot. Veg. 18:168, 2003. (2) P. Umaharan et al. Phytopathology 88:1262, 1998.