When conditions are just right, nature can hold a usually nasty fungus in such check that something special happens. Instead of destroying a crop, the fungus creates grapes with incredibly concentrated flavor that can make some of the world\u2019s sweetest, most precious wines.\r\n\r\nThe fungus, Botrytis cinerea, is more affectionately known as \u201cnoble rot.\u201d\r\n\r\nIt\u2019s the same kind of rot that spoils strawberries and soft fruit with greyish fuzz. So what makes this mold noble?\r\n\r\nIt comes down to a fine balance of moisture, sunlight and temperature. Ripe, healthy grapes must still be on the vine as fall begins, when misty mornings can provide the moisture that the fungus needs to thrive. It will pierce a grape\u2019s skin to feast on its juice.\r\n\r\nAfter a few hours, sunshine and otherwise dry conditions must follow. This evaporates moisture and stops the fungus in its tracks. The following morning, the process repeats itself.\r\n\r\nA succession of misty mornings and dry, sunny days provide the perfect conditions as sugars, flavors and acids concentrate in the grape while the fungus consumes water. It\u2019s risky business, as rain can turn this delicate interaction into full-blown rot. In some years, growers lose their entire crop.\r\n\r\nBotrytized grapes aren\u2019t pretty, as they turn shriveled and brown. Their juice, however, is golden, sweet and precious. Each grape needs to be handpicked individually, and yields are tiny. The resulting wines are complex, concentrated and can age for decades.\r\n\r\nIn a few places, the crucial elements responsible for botrytis occur year after year, and all are famed for their noble sweet wines. Here are some of the best.\u00a0\u2014Anne Krebiehl, MW\r\n\r\n\r\nTokaj\r\nThe Tokaj-Hegyalja region in northeast Hungary and southeast Slovakia is said to be home to the oldest botrytized wines in the world, known as Tokaj or Tokaji Azs\u00fa (which historically meant \u201cdried\u201d in Hungarian, though today it\u2019s almost exclusively associated with wines made from noble rot). Slopes that bear Furmint, H\u00e1rslevel\u0171 and Yellow Muscat, the three main grapes of Tokaj,\u00ad receive early morning fog that wafts off the nearby Tizsa and Bodrog rivers. This creates ideal conditions for botrytis.\r\n\r\nThe shriveled grapes are harvested separately in 20-liter buckets called puttonyos. A paste made from these crushed grapes is added to base wine produced from unbotrytized grapes, and then a second fermentation takes place in barrel.\r\n\r\nTraditionally, the number of puttonyos used has been proportional to the sweetness level of Tokaji, with six puttonyos at the top of the scale and five puttonyos slightly less sweet. Wines that were previously designated three or four puttyonos are now labeled late harvest or szamorodni. The sweetest Tokaji, Eszencia, uses the free run juice of azs\u00fa berries. Eszencia wines have extremely high sugar content, typically 500\u2013700 grams per liter, and low alcohol.\r\n\r\nClassic pairings for Tokaj include foie gras (Hungary is the world\u2019s leading producer) or Hungarian crepes.\u00a0\u2014Jeff Jenssen\r\n\r\nPatricius 2006 Asz\u00fa Six Puttonyos (Tokaj); $65/500 ml, 95 points. Tantalizing aromas of apricot, bananas foster, beeswax and pineapple upside-down cake transfer seamlessly onto the palate. It then opens up further, with pronounced flavors of lemon meringue and acacia honey. The texture is luxurious, silky and voluptuous. Blue Danube Wine Co. Editors\u2019 Choice.\r\n\r\n Samuel Tinon 2007 Dry Tokaji Szamorodni (Tokaj); $46/500 ml, 92 points. Amber in color, with aromas of caramel and dried raisins. Rich flavors of dried fruits, stewed plums and wine-soaked raisins combine before a juicy yet persistent finish. Blue Danube Wine Co.\r\n\r\n\r\nAustria\r\nIn Burgenland, which lies in Austria\u2019s warmer east, one body of water creates perfect conditions for botrytis: Lake Neusiedl. The shallow lake ensures misty mornings with enough moisture for botrytis to develop. The villages on its shore have long been famed for their sweet wines. The town of Rust even used local sweet wine, known as ausbruch, to buy its free town status from the Austrian emperor in 1681.\r\n\r\nHeidi Schr\u00f6ck is one producer that still makes Ruster Ausbruch today, which can only be made in Rust. According to Schr\u00f6ck, the varieties best suited to making fully botrytized ausbruch are late-ripening Welschriesling and Furmint, for their piquancy and acidity, and Pinot varieties, for their creaminess.\r\n\r\nShe usually harvests just 160 liters of juice per acre, which is painfully low and explains some of the lofty price tags on these rare wines. Less botrytis-affected grapes are made into sp\u00e4tlese and auslese styles.\r\n\r\nLocated on the opposite, eastern shore of Lake Neusield in the town of Illmitz is Weinlaubenhof Kracher. Gerhard Kracher, who manages the family estate, believes that Welschriesling, Chardonnay, Scheurebe and Muskat Ottonel are best suited to make fine trockenbeerenauslesen, or TBAs, on the local soils. Even the red grape Zweigelt makes lovely botrytized wines, he says.\r\n\r\nSome of Kracher\u2019s vineyards are less than 1,000 feet from the lake. While botrytis comes every year, he has to wait for the right conditions, which means harvest can take place anytime from October to December.\r\n\r\nKracher suggests to serve TBA or ausbruch in a white wine glass at 54\u00b0F, with classic pairings like blue or soft, washed-rind cheeses, goose liver parfait or Austrian desserts like apfelstrudel (apple strudel), marillenkn\u00f6del (sweet apricot dumplings) or pancakes with apricot jam.\r\n\r\nSchr\u00f6ck proposes more adventurous matches, something she signals on her quirky labels. She fights to get these sweet wines out of the cheese or dessert corner.\r\n\r\n\u201cDepending on the acidity and character of the wine, other dishes work well,\u201d she says. \u201cEspecially high-acid wines pair well with saltiness, ginger, chili and rosemary. Ausbruch can even work with peppered steak.\u201d\u00a0\u2014Anne Krebiehl, MW\r\n\r\nKracher 2013 Scheurebe Trockenbeerenauslese Nummer 5 Zwischen den Seen (Burgenland); $95/375 ml, 97 points. Candied lime and lemon zest are bathed in the rich honey notes of full-blown botrytis. Candied quince and mandarin peel run circles around honeycomb and apricot jam. Terlato Wines International.\u00a0abv: 9.5%\r\n\r\nHeidi Schr\u00f6ck 2014 Ruster Ausbruch Turner (Burgenland); $160/375 ml, 96 points. A blast of beeswax and honey provides heady lift. The palate is tooth-breakingly sweet, but it comes with that honeyed, candied-\u00adcitrus thrill. Sufficient bright acidity counters the richness. The mouthfeel is full, oily and viscous, with notes of honeycomb and beeswax. Skurnik Wines, Inc.\r\n\r\nGunter Triebaumer 2013 Ruster Ausbruch Welsch\u00adriesling (Burgenland); $35/375 ml, 94 points. Scents of candied lemon and rich blossom honey are lifted and intense. A touch of smoky stone can be glimpsed before the sweetness takes over. Candied-citrus notes swish across the palate, which trails blossom, honey, nectar and candied peel. The finish is fresh and clean. Magellan Wine Imports.\u2014A.K.\r\n\r\n\r\nGermany\r\nKissed by edelf\u00e4ule, as the malevolent fungus is known here, the great botrytized wines of Germany are defined by wonderful perfume and juicy, sweet fruit balanced against electric acidity.\r\n\r\nRiesling, with its precision, intense aromatics and complexities of fruit, spice and mineral, is considered the noblest of botrytis-friendly grapes here. While typically light in body and alcohol, they vary from the racy, lime- and slate-scented delights of the Mosel to riper, more tropical Rieslings of Rheingau, Nahe or Pfalz.\r\n\r\nThe warmer regions of Rheingau, Nahe and Pfalz are also home to honeyed Scheurebe wines, with distinct blackcurrant and grapefruit notes. In the Franken region, Riesling, as well as varieties like Silvaner and Rieslaner, often yield more muscular yet sublimely herb-inflected wines.\r\n\r\nIt\u2019s no coincidence that Germany\u2019s greatest botrytized wines originate from vineyards that overlook the Mosel, Rhine, Nahe or Main rivers and their various tributaries. Large bodies of water adjacent to vineyards moderate cool, northerly climates and allow grapes to ripen through an extended growing season. Mist formed by the rivers contributes humidity that encourages botrytis growth and the transformation of pristine grapes into shriveled fruit bombs of sugar, spice and acidity.\r\n\r\nTo preserve primary fruit character and vibrant acidity, German winemakers typically avoid techniques like new oak fermentation and maturation, which alters aromas and flavors, or malolactic fermentation, which rounds the palate and softens acidic edges.\r\n\r\nRobert Weil, one of the Rheingau\u2019s most prestigious winemakers, has long produced both dry and botrytized Riesling. According to Nicolas Pfaff, the winery\u2019s export director, delicacies like fois gras are classic pairings for botrytized Riesling. Frequent travels around the globe with Weil, however, have given Pfaff a greater understanding into these wines\u2019 dexterity.\r\n\r\n\u201cI had a wine dinner in Bangkok, and it was just fantastic,\u201d says Pfaff. Pairing perfumed, sweet-and-spicy Thai cuisine with only sp\u00e4tlese, auslese and beerenauslese wines (all concentrated in sweetness by botrytis) resulted in a fascinating explosion of flavors, he says.\u00a0\u2014Anna Lee C. Iijima\r\n\r\n Robert Weil 2015 Kiedrich Gr\u00e4fenberg Riesling Trockenbeerenauslese (Rheingau);\u00a0$775/375 ml, 98 points. Layers of spicy saffron, peach, honey and caramel on the nose. The sweet-tart palate is deft and spry, yet it\u2019s deep and lush in flavor. Spine-tingling acidity darts through a honeyed, waxy finish. It will continue to improve for decades. Loosen Bros. USA. Cellar Selection\r\n\r\n Dr. Loosen 2006 Graacher Himmelreich Riesling Beerenauslese (Mosel); $174/375 ml, 95 points. Feather-light in texture yet deeply penetrating in flavor, this offers rolling waves of sweet caramel, honey and stone fruit flavors. It\u2019s luscious and mouthfilling in texture, but it\u2019s balanced by strikes of lime acidity and a dry, pristine finish. Loosen Bros. USA. Editors\u2019 Choice\r\n\r\nDr. H. Thanisch (Erben M\u00fcller-Burggraef) 2015 Berncasteler Doctor Riesling Auslese (Mosel); $50/375 ml, 92 points. Pristine honey and tangerine sweetness falls on the palate in a delicate pattern here. It\u2019s breathtakingly light in body yet unctuous and concentrated. Sunny citrus acidity leads a long, slightly spicy finish. Winesellers, Ltd.\r\n\r\n\r\n\r\n\r\nLoire Valley\r\nThe beauty of botrytis is that it\u2019s rare. Only two regions of the Loire Valley (which surrounds the Loire, France\u2019s longest river) are designated as consistent enough to make botrytized wine: Layon River Valley (a Loire tributary) and Vouvray, on the Loire. Both rely on thin-skinned Chenin Blanc that balances crisp delicacy and extreme richness.\r\n\r\nSeveral appellations capture essential morning mists from the steep Layon riverbanks, which include Coteaux du Layon and village-designated Coteaux du Layon, such as Beaulieu, Chaume, La Faye or Saint-Aubin. The greatest selections, however, are from Quarts de Chaume (Loire\u2019s only grand cru) and Bonnezeaux.\r\n\r\nVouvray, 80 miles up river, produces every style of white wine from versatile Chenin Blanc. Botrytized wines are produced in small quantities and are frequently richer than those from the Layon. A visit to the limestone caves where the wines are stored reveals old vintages still full of life, which illustrates how well these opulent treasures can age.\r\n\r\nThese are dinner wines. Both regions specialize in decadent cream sauces with local river fish, just right for the balance of richness and acidity found in the wines.\u00a0\u2014Roger Voss\r\n\r\nCh\u00e2teau de Fesles 2011 Vin Rare (Bonnezeaux); $40/500 ml, 95 points. A golden wine that balances intense acidity with honeyed botrytis flavors. Ripe peaches and pineapples dominate the fruit profile of this concentrated, beautiful wine. It\u2019s just approaching its peak, so wait until 2018. Advantage International. Editors\u2019 Choice\r\n\r\nDomaine du Petit M\u00e9tris 2014 Grand Cru (Quarts de Chaume); $65/500 ml, 94 points. This wine, with its opulent honey and spice character, is full of yellow fruit notes, and it keeps freshness that lifts the richness of the wine. This wine is still very young, so don\u2019t drink before 2022. Boutique Wine Collection. Cellar Selection\r\n\r\n\r\nBordeaux and \u00a0Southwest France\r\nSauternes is rooted in fluvial white-pebble and limestone outcrops that enhance the magical combination of S\u00e9millon and Sauvignon Blanc. South of the city of Bordeaux, it\u2019s a land of winding roads, crumbling stone walls and majestic fortresses.\r\n\r\nThe wine\u2019s sweetness is thanks to the meandering Ciron River that emerges from the pine forests of the Landes. The river carries its moisture and autumnal morning mists before it continues into the nearby Garonne river.\r\n\r\nOn the other bank of the Ciron is Barsac, with similar but softer alluvial terraces. It\u2019s the equal of Sauternes in the production of magnificent botrytized wines. Barsac offers delicate wines of great finesse, as opposed to the more powerful selections from Sauternes. Together, these appellations make some of the greatest botrytized wines in the world, like Yquem, Rieussec, Suduiraut, Climens and Coutet. Sauternes and Barsac are capable of aging for decades.\r\n\r\nWithin the greater Southwest, two appellations are worth exploration for reasonably priced botrytized gems that fly under the radar. Monbazillac, on the Dordogne River, offers a lighter taste from the same white grapes common to Bordeaux. Gaillac, located on the Tarn River northeast of Toulousse, relies on Mauzac for its botrytized wines.\r\n\r\nIn Bordeaux and the Southwest, these are not widely considered dessert wines, but instead are served as an ap\u00e9ritif that\u2019s accompanied by local foie gras.\u00a0\u2014Roger Voss\r\n\r\nCh\u00e2teau Coutet 2011 Barsac; $84, 96 points. Well balanced, this gorgeously ripe wine is packed full of fresh yellow fruits, ripe oranges and lemon. The fruit counterpoints the generous, dense structure that offers the dry core of botrytis. Acidity gives a line of freshness at the end. Drink from 2020. Millesima USA.\r\n\r\nDomaine de Grange Neuve 2011 La Fleur Lily (Monbazillac); $19/500 ml, 90 points. This is a fine, yet ripe, wine. It has an intense botrytis character that balances dryness with considerable sweetness. The wine, rich in honey and marmalade flavors, is opulent, decadent and ready to drink. LVC Las Vegas Inc. Editors\u2019 Choice.\r\n\r\n\r\nAlsace\r\nIn Alsace, a region in northern France, wines made from fully botrytized grapes are known as Selection des Grains Nobles (SGN), which is French for \u201cselection of noble berries.\u201d They\u2019re made from Riesling, Pinot Gris, Gewurztraminer and Muscat, and while they\u2019re very sweet, the best examples also exhibit high acidity for balance.\r\n\r\nThomas Mur\u00e9, of Domaine Ren\u00e9 Mur\u00e9, says that for a good SGN, \u201cbotrytis must develop on ripe grapes. If that happens early in the season, you get fresh aromas with higher acidity.\u201d\r\n\r\nThe varieties permitted for SGN produce markedly different wines, says Mur\u00e9.\r\n\r\n\u201cRiesling, my favorite, makes crystalline wines,\u201d he says. \u201cMuscat is floral. Pinot Gris is very rich and has lots of candied fruit notes, while Gewurztraminer turns out very exotic, with delicate notes of rose.\u201d\r\n\r\nGrapes partially affected by botrytis can be made into a Vendanges Tardives, or late-harvest wine. While sweet, they are lighter, milder and more versatile than SGNs. Mur\u00e9 typically matches SGNs with blue cheeses and aged, hard cheeses, and he\u2019s even paired Riesling SGN with feathered game.\u00a0\u2014Anne Krebiehl, MW\r\n\r\n Ren\u00e9 Mur\u00e9 2010 Vorbourg Grand Cru Clos Saint Landelin Vendanges Tardives Gewurztraminer (Alsace); $65, 95 points. Ripe peach hits the nose at once, followed by glimpses of marmalade and peach compote. The palate follows with the same aromatic intensity, which enriches the peach compote notes even further with lemony barley sugar and fresh caramel, pierced by tangy citrus acidity. Drink now through 2030. Gargouille Collection.\r\n\r\n Domaine Barm\u00e8s-Buecher 2007 Hengst Grand Cru S\u00e9lection de Grains Nobles Gewurztraminer (Alsace); $145/500 ml, 94 points. A wealth of notions hits the palate: baked apple, fir honey, lemon-scented caramel and burnt sugar. Caramel-crusted apricots glow on the palate, while everything is lit up with bright, fresh acidity that highlights apricot, apple and honey. Petit Pois.