The effect of the citrus tristeza disease caused by CTV on vegetative, productive, and industrial characters of the sweet orange 'Valencia' grafted onto seven hybrid progenies of full sibs segregating for tolerance was studied. The hybrids were originated from controlled crosses between the commercial rootstocks 'Davis A' Poncirus trifoliata (T), Sunki mandarin (S), 'São Paulo' sour orange (A) and 'Limeira' Rangpur lime (C). Two sets of hybrids were studied. The first was formed by 298 individuals, from which 20 were T x S, 67 S x T, 98 S x A, 48 C x A, and 65 T x A. The second set had 1.243 hybrids, being 845 S x A, 240 A x S, 139 C x A, and 19 A x C. In the nursery, tristeza disease was responsible for 21% of death among the intolerant individuals, while among survivors transplanted to the field, an additional 13% died in a four-years period. Among the intolerant survivors in the field, tristeza reduced in four years rootstock diameter to 41%, scion diameter in 45%, and general vigor in 42%. Fruit weight was reduced in 22% in average. Yield was the most drastically affected character, being reduced to 41% in the first harvest, and up to 90% in the fifth harvest. Accumulated yields of five years were reduced 85% in the intolerant segregants among the different groups of hybrids. Productivity (yield/area of canopy) was also intensely affected (46%) indicating that the reduction in yield was proportionally more intense than the correspondent reduction in the vegetative growth. The relation between scion/rootstock diameters decreased 7% in the intolerant plants. Although small, it indicated that the vegetative growth of the tolerant canopies was more affected than the rootstocks, despite their intolerance. Little or no effect was detected on external peel color, juice outturn, and soluble solids/acids ratio. Acidity and soluble solids significantly increased at an average of 12 and 14%, respectively, in the intolerant hybrids.
Citrus; CTV; yield; growth; ºBrix
