Time filter

Source Type

Davis, CA, United States

Harel-Beja R.,Newe Yaar Research Center | Tzuri G.,Newe Yaar Research Center | Portnoy V.,Newe Yaar Research Center | Lotan-Pompan M.,Newe Yaar Research Center | And 26 more authors.
Theoretical and Applied Genetics | Year: 2010

A genetic map of melon enriched for fruit traits was constructed, using a recombinant inbred (RI) population developed from a cross between representatives of the two subspecies of Cucumis melo L.: PI 414723 (subspecies agrestis) and 'Dulce' (subspecies melo). Phenotyping of 99 RI lines was conducted over three seasons in two locations in Israel and the US. The map includes 668 DNA markers (386 SSRs, 76 SNPs, six INDELs and 200 AFLPs), of which 160 were newly developed from fruit ESTs. These ESTs include candidate genes encoding for enzymes of sugar and carotenoid metabolic pathways that were cloned from melon cDNA or identified through mining of the International Cucurbit Genomics Initiative database (http://www. icugi. org/). The map covers 1,222 cM with an average of 2.672 cM between markers. In addition, a skeleton physical map was initiated and 29 melon BACs harboring fruit ESTs were localized to the 12 linkage groups of the map. Altogether, 44 fruit QTLs were identified: 25 confirming QTLs described using other populations and 19 newly described QTLs. The map includes QTLs for fruit sugar content, particularly sucrose, the major sugar affecting sweetness in melon fruit. Six QTLs interacting in an additive manner account for nearly all the difference in sugar content between the two genotypes. Three QTLs for fruit flesh color and carotenoid content were identified. Interestingly, no clear colocalization of QTLs for either sugar or carotenoid content was observed with over 40 genes encoding for enzymes involved in their metabolism. The RI population described here provides a useful resource for further genomics and metabolomics studies in melon, as well as useful markers for breeding for fruit quality. © 2010 Springer-Verlag. Source

Mercier J.,HM. Clause | Muscara M.J.,HM. Clause | Davis A.R.,HM. Clause
Plant Disease | Year: 2014

In September and October 2012, powdery mildew was detected on watermelon (Citrullus lanatus var. lanatus) plants of various breeding lines growing in field plots in Davis, California. Plants had partially necrotic leaves, yellowing to brown in color, with white surface mycelium and faint sporulation. No teleomorph was observed. Infected leaves were collected for examination and a spore suspension of the field isolate was made in water with 0.01% Tween 20 to spray inoculate watermelon seedlings of cultivar Dixie Lee with two true leaves. Plants were incubated in a growth chamber (22 to 26°C, 12-h photoperiod) for approximately 10 days, until sporulation was apparent. Microscopic observation of conidial chains showed that they had clearly crenate edges indicative of Podosphaera xanthii (4). To confirm the identity of the pathogen, we used Podosphaera-specific primers PFITS-F (5′-CCAACTCGTGCTGAGTGT-3′) and PF5.8-R (5′-TGTTGGTTTCTTTTCCTCCG-3′) to amplify and sequence the internal transcribed spacer regions of the nuclear rDNA. The 326-bp sequence had 98% homology to the GenBank sequence (accessions JQ340082.1 and AB774158.1) for P. xanthii. Infected 'Dixie Lee' leaves were used to make a spore suspension (approximately 5 × 104 conidia/ml) as described above to inoculate watermelon, melon, and squash seedlings (2 to 3 plants per cultivar) in a greenhouse. It caused severe symptoms on all watermelon plants cv. Charleston 76, P8, and Sugar Baby in the form of a powdery mildew with surface mycelium and chains of conidia, with leaves becoming gradually more necrotic and eventually dying, with the appearance of a melting down. Non-inoculated plants did not develop symptoms. The isolate also infected all squash plants 'Zucchini Elite' and melon powdery mildew differentials Iran H and 'Védrantais.' On these plants, the pathogen produced a powdery mildew (white surface mycelium with sporulation) but did not cause extensive necrosis. All other melon powdery mildew differentials ('PMR5,' 'PMR45,' WMR29, MR1, PI 124112, and PI 313970) did not develop any powdery mildew. A follow-up test in a growth chamber (22 to 26°C, 12-h photoperiod) with the same set of species and cultivars gave the same results. Based on these results, we conclude that this isolate belongs to race 1W (1,2). The presence of race 1W could have implications in disease management for this crop in the Central Valley of California as most cultivars are not resistant to it and the disease has been shown to cause severe damage in other states (1,3). © The American Phytopathological Society. Source

Discover hidden collaborations