Synthetic hexaploid wheat (SHW) has shown effective resistance to a diversity of diseases and insects, including tan spot, which is caused by Pyrenophora tritici-repentis, being an important foliar disease that can attack all types of wheat and several grasses. In this study, 443 SHW plants were evaluated for their resistance to tan spot under controlled environmental conditions. Additionally, a genome-wide association study was conducted by genotyping all entries with the DArTSeq technology to identify marker-trait associations for tan spot resistance. Of the 443 SHW plants, 233 showed resistant and 183 moderately resistant reactions, and only 27 were moderately susceptible or susceptible to tan spot. Durum wheat (DW) parents of the SHW showed moderately susceptible to susceptible reactions. A total of 30 significant marker-trait associations were found on chromosomes 1B (4 markers), 1D (1 marker), 2A (1 marker), 2D (2 markers), 3A (4 markers), 3D (3 markers), 4B (1 marker), 5A (4 markers), 6A (6 markers), 6B (1 marker) and 7D (3 markers). Increased resistance in the SHW in comparison to the DW parents, along with the significant association of resistance with the A and B genome, supported the concept of activating epistasis interaction across the three wheat genomes. Candidate genes coding for F-box and cytochrome P450 proteins that play significant roles in biotic stress resistance were identified for the significant markers. The identified resistant SHW lines can be deployed in wheat breeding for tan spot resistance.

Spot blotch (SB) caused by Bipolaris sorokiniana (Sacc.) Shoem is a destructive fungal disease affecting wheat and many other crops. Synthetic hexaploid wheat (SHW) offers opportunities to explore new resistance genes for SB for introgression into elite bread wheat. The objectives of our study were to evaluate a collection of 441 SHWs for resistance to SB and to identify potential new genomic regions associated with the disease. The panel exhibited high SB resistance, with 250 accessions showing resistance and 161 showing moderate resistance reactions. A genome-wide association study (GWAS) revealed a total of 41 significant marker–trait associations for resistance to SB, being located on chromosomes 1B, 1D, 2A, 2B, 2D, 3A, 3B, 3D, 4A, 4D, 5A, 5D, 6D, 7A, and 7D; yet none of them exhibited a major phenotypic effect. In addition, a partial least squares regression was conducted to validate the marker–trait associations, and 15 markers were found to be most important for SB resistance in the panel. To our knowledge, this is the first GWAS to investigate SB resistance in SHW that identified markers and resistant SHW lines to be utilized in wheat breeding.

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Fruits of five regional selections of rambutan (Nephelium lappaceum L.) were characterized to identify those with international marketing quality to promote their propagation in Mexico, improvement and conservation in germoplasm bank. The fruits were harvested in June, July, and August 2008 and, after each harvest, were assessed for shape (length/diameter), firmness, fruit weight, number of fruits per kilogram, weight and percentage of pericarp, seed and aril, total soluble solids, total sugars, vitamin C content, pH, and titratable acidity. In addition, a sensorial evaluation was carried out with 31 panelists who graded each selection for color, sweetness, and acidity. Fruits of five selections were ovoid, and with the following characteristics: firmness values from 43.7 to 51.0 N, fruit weight ranged from 22.4 to 34.7 g, registering from 28.9 to 45.0 fruits per kg; pericarp weight from 10.5 to 17.3 g (45.9 to 49.9% of the total fruit weight); total seed weight from 2.2 to 2.5 g (7.0 to 10.0%); average arils weight from 8.9 to 13.1 g (37.5 to 41.4%). The fruits had high contents of total soluble solids (17.8 to 20.4 ºBrix), total sugars (211.95 to 242.70 mg/100g in the edible portion), vitamin C (37.9 to 69.1 mg/100 g), pH 5.0, and titratable acidity of 0.20 to 0.28%. The fruits from the RT-01 and RT-05 selections had better attributes in fruit weight, total soluble solids and titratable acidity and were better accepted by the panelists. Harvest date significantly affects rambutan fruit quality; at the middle and end of the season harvested fruits had better qualitative characteristics for the marketing.

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