Avaliação horitcultural da laranjeira 'Folha Murcha', tangerineira 'Satsuma' e limeira ácida 'Tahiti' sobre doze porta-enxertos

Abstract

Horticultural evaluation of 'Folha Murcha' sweet orange, 'Satsuma' manadarin and 'Tahiti' lime on twelve rootstocks Brazilian citriculture is mainly based on one rootstock cultivar, the 'Cravo' Rangpur lime, exploring a restricted number of scion cultivars. This situation limits the expansion of citrus production for fresh fruit export, due to the limited number of cultivars in use. Besides, near 80% of citrus orchards are located in an area of approximately 600,000 ha, in the São Paulo State and the southern region of the Minas Gerais State. These facts also impose a large phytossanitary vulnerability to citrus production, due to the increasing threats of pests and diseases outbreaks, that cause productivity decrease and higher costs for orchard establishment and management. The Citrus Variegated Chlorosis (CVC), caused by the xylem-limited bacterium, Xylella fastidiosa, is one example of such threats. This disease is extremely severe in sweet oranges, causing size reduction ad quality deterioration of fruits, that become unsuitable for fresh consume or juice processing. The losses associated to CVC have been recently estimated in 10-14% of the total comercial crop in São Paulo State. CVC management is currently based on the use of healthy nursery plants, pruning of injured branches and control of the vectors. In addition to these strategies, it is important to maintain adequate cultural practices for orchard management. Nonetheless, the utilization of resistant cultivars is an indispensable strategy to co-exist with the disease in the long term. This study was aimed to evaluate the horticultural performance of 'Folha Murcha' sweet orange, 'Okitsu' Satsuma mandarin and 'Tahiti' lime grafted onto twelve rootstocks. 'Okitsu' Satsuma mandarin and 'Tahiti' lime are assymptomatical species in relation to CVC, with potential to be produced in small areas. The 'Folha Murcha' sweet orange has demonstrated high tolerance to CVC, when compared with other sweet orange cultivars. The trials were conducted at the Estação Experimental de Citricultura de Bebedouro, (EECB), and were planted in 2001. Evaluations of plant growth, yield and fruit quality were carried out in all the trials, during three years. In the 'Folha Murcha' trial, additional evaluations of CVC tolerance were conducted. In the non-irrigated trials, tree water deficit tolerance was evaluated by two methods: visual assessment of water stress and direct leaf color measurements. In 'Tahiti' lime, peel color of export fruits was measured and a quantitative methodology was defined as an alternative for current classification criteria, which are based on the subjective visual inspection of external fruit aspect. The horticultural evaluation of 'Folha Murcha' sweet orange, 'Okitsu' Satsuma mandarin and 'Tahiti' lime onto twelve rootstocks allowed to identify the trifoliate rootstocks 'Flying Dragon', 'Rubidoux' and 'FCAV' as alternatives to 'Cravo Limeira'.