Fungos micorrízicos arbusculares em porta-enxertos de citros

Abstract

The present work had the objective of studying the mycorrhizal dependency of citrus rootstocks, traditionally used in citrus orchards and hybrids from the citrus breeding program from Embrapa Cassava & Fruits, in the city of Cruz das Almas, State of Bahia, Brazil, which have presented important characteristics for adaptation to the Coastal Tablelands ecosystem, with interest in drought and aluminum tolerance. In addition, the mycorrizal colonization of hybrids selected as promising rootstocks and traditional rootstocks was determined under field conditions, in the Citrus Germplasm bank of Embrapa Cassava & Fruits. Fine roots collected in November of 2002 and July of 2003, in citrus orchards of grafted plants with Pera orange as the scion plant, and with ungrafted rootstocks HTR-051, Sunki x Poncirus trifoliata selection English 264, Cleopatra x Carrizo 226citrange (Citrus sinensis x P. trifoliata), Rangpur lime (C. limonia Osbeck) and Cleopatra mandarin (C. reshni Hort. ex Tan.), inoculated with different species of arbuscular mycorrhizal fungi. All citrus rootstocks presented high percentages of root colonization, varying from 42% to 83%, even in high soil phosphorus conditions. The rootstocks HTR 051, Cleopatra mandarin e Cleopatra x Carrizo 226 citrange presented the greater mycorrhizal dependency, and Sunki x Poncirus trifoliata selection English 264 had the lowest mycorrhizal dependency. The species Acaulospora sp., Glomus clarum, and Glomus etunicatum were efficient for growth promotion of citrus rootstocks in a plant growing substrate with 32 mg.dm-3 of available phosphorous, while the species Gigaspora margarita and Gigaspora albida inhibited plant growth. Gigaspora albida was efficient for growth promotion in a plant growing substrate with 8 mg.dm-3 of available phosphorous.