Rootstock breeding for resistance to grapevine decline and dieback in southern Brazil

Abstract

Grapevine decline and dieback is a serious problem for grape production in southern Brazil. It is characterized by a set of symptoms that lead to the weakening and death of affected plants. The main causes are a root scale, the ground-pearl (Eurhizococcus brasiliensis), associated with soil fungi (Cylindrocarpon, Fusarium, Phaeacrimonium and others), and high-clay-content soils. Apparently, the root wounds caused by ground-pearl under poorly aerated soil conditions allow the entrance of root decay fungi, resulting in plant death. The creation of grape rootstocks resistant to root decay fungi is one objective of the grape breeding program at Epagri, the Agricultural Research Enterprise of Santa Catarina State, Brazil. The first step was the identification of resistance sources. In rootstock trials carried out in areas where high mortality rates were previously observed, all traditional rootstocks were highly susceptible. Vitis caribaea hybrids showed a high level of resistance but also some defects, such as excessive vigor and absence of winter dormancy. Some genotypes of Vitis shuttleworthii and Vitis palmata, originating from the waterlogged soil conditions of the Everglades (Florida, USA), also showed a high level of resistance. However, the performance of these genotypes and their descendants under dry soil conditions was very poor, and more generations of crossing will be necessary to eliminate undesirable characters. The most promising breeding lines resulted from self pollination of the rootstock IAC 572 (V. caribaea × 101-14Mgt). The selection process started from 840 seedlings and resulted in 23 selections that showed no symptoms of vine decline at three different sites. These selections are being evaluated now for productivity and fruit quality in rootstock trials with different scion cultivars.