Sustainable viticulture is one of the main challenges for our sector, and one possible solution is the use of resistant hybrids. The OIV, as an intergovernmental organisation, works in this area with a goal of harmonising definitions for all grapevine materials, including hybrids. It should be noted that hybrids are commonly used in non-European countries, and not only for research purposes. Some project resolutions have been discussed in the past and some of them are being developed by the OIV. However, before going deeper into the harmonisation processes, some genetic aspects should be defined in order to establish an international scientific consensus. Once this is accomplished, the OIV could then discuss the pressing issue of labelling or regulations on the denomination of varieties and also of the wines produced for the entire vitivinicultural sector.

Background and Aims Several studies have shown that cover crops restrict the development of shallow grapevine roots and reduce vigour and yield in the vineyard. The objective of this study was to evaluate the long‐term effects, after 8 years, of four soil management practices on grapevine root development and on yield in irrigated vineyards under semi‐arid conditions. Methods and Results Four soil management treatments were established in the inter‐row: no‐tillage with herbicide application (herbicide treatment), tillage (tillage treatment), no‐tillage with self‐seeding annual grass cover crop [self‐seeding annual grass cover crop treatment (AGT)] and tillage with annual cereal seeding [annual cereal treatment (CT)]. The density of lignified grapevine roots was determined using the trench method during grapevine dormancy. The treatments CT and AGT increased grapevine root density as compared to bare soil treatments. In addition, annual cereal treatment and AGT reduced vigour and yield but only in extremely dry years. Conclusions Unlike previous studies on cover crops, our results show that annual cover crops enhance grapevine root growth both under the row and in the inter‐row as compared to bare soil management. The increased grapevine root growth was mainly due to the proliferation of fine roots (diameter less than or equal to 1 mm), while yield reduction was mainly due to fewer berries per bunch. Significance of the Study This study proves that coupling cover crop management with the grapevine growth cycle under irrigated semi‐arid conditions can improve vineyard sustainability with an average yield reduction of less than 15%. To achieve this goal, cover crop competition must be avoided during the stages of the grapevine most sensitive to water deficit or during periods of low water availability. These are mainly during fruitset and ripening.

Considerando que se trata de un trabajo original de investigación, que reúne todos los requisitos establecidos en el RD 1393/2007, de 29 de octubre, autorizo su presentación y defensa pública.Lo que afirmo en Madrid, a 4 de julio de dos mil ocho, para que conste a los efectos oportunos. Fdo. José Ramón Lissarrague García-Gutiérrez LISTA DE ABREVIATURASA:Tasa de asimilación de CO 2 (µmol•m -2 •s -1 ) A/Gs Eficiencia intrínseca en el uso del agua A/PAR: Curva de respuesta fotosintética foliar a la luz ABA:Ácido abscísico A max:Fotosíntesis máxima en condiciones de saturación luminosa (µmol•m -2 •s -1 ) cv.: Cultivar C: Cuajado CS: Cabernet Sauvignon D: Desborre DOY o DD1: Día del año DH: Número medio mensual/anual de días de helada DPV: Déficit de presión de vapor (kPa) E: Envero E: Espaldera (tratamiento) E: Transpiración ETc: Evapotranspiración del viñedo (mm) ETo: Evapotranspiración de referencia (mm) F: Floración GDC: Geneva double courtain G.D.D.: Integral térmica eficaz (base 10ºC) (growing degree days) en º•día ó grado•día. Gs: Conductancia estomática diurna (mmol H 2 O/m 2 •s) Gsmax: Conductancia estomática máxima, en saturación luminosa (mmol H 2 O/m 2 •s) H veg:Altura de la vegetación en la espaldera Hn:Hoja de nieto Hp:Hoja principal Hr:Humedad relativa media (%) hs:Horas solares HS:Número medio mensual/anual de horas de sol IF:Índice foliar Ic:Punto de compensación a la luz (µmol•m -2 •s -1 ) Is:Punto de saturación a la luz (µmol•m -2 •s -1 ) IR:Índice de Ravaz IPT:Índice de polifenoles totales K:Coeficiente de extinción K:Valor del PAR al que se obtiene la mitad de la fotosíntesis máxima (µmol•m -2 •s -1 ) kc:Coeficiente de cultivo LAI:Índice de área foliar total (Leaf Area Index) en m 2 hoja/m 2 suelo LLN:Número de capas de hojas LPI:Índice de plastocrono de la hoja (leaf plastochron index) M Hn:Materia seca de hojas de nieto (g•sarmiento -1 ) M Hpp:Materia seca de hojas principales (g•sarmiento -1 ) M Productiva: Materia seca de los órganos productivos (g•sarmiento -1 y g•m -2 ) M Rac:Materia seca de racimos (g•sarmiento -1 ) M Tn:Materia seca de tallos de nieto (g•sarmiento -1 ) M Tpp:Materia seca de tallo principal (g•sarmiento -1 ) M Vegetativa: Materia seca de los órganos vegetativos (g•sarmiento -1 y g•m -2 ) MAD:Maduración MS Total:Materia seca total producida (g•sarmiento -1 y g•m -2 ). P:Precipitación (mm) PAR:Radiación fotosintéticamente activa incidente (µmol•m -2 •s -1 ) Pe:Precipitación efectiva (mm) PMP: Peso de madera de poda (kg•m -2 ) P100b:Peso fresco de 100 bayas (g) R 2 :Coeficiente de determinación R:Coeficiente de reflexión del conjunto planta suelo R/FR: Relación rojo/infrarrojo cercano Rd:Respiración diurna (µmol CO 2 •m -2 •s -1 ) Ra:Radiación absorbida Ra E:Radiación absorbida por la cara Este de la planta Ra O:Radiación absorbida por la cara Oeste de la planta Ra (s):Radiación absorbida por el suelo Ri:Radiación incidente Rit:Radiación interceptada Rt:Radiación transmitida Rr (s):Radiación reflejada por el suelo Rr (sp):Radiación reflejada por suelo y planta Rs:Coeficiente d...