The genetics of tolerance to tristeza disease in citrus rootstocks

Abstract

Controlled pollinations between four elite citrus rootstocks, Citrus limonia -'Limeira' rangpur lime (Cravo), C. sunki -'Sunki' mandarin (Sunki), C. aurantium -'São Paulo' sour orange (Azeda) and Poncirus trifoliata -'Davis A' trifoliate orange (Trifoliata), resulted in 1614 nucelar and 1938 hybrid plants identified by the isozyme loci Pgi-1, Pgm-1, Got-1, Got-2, Aps-1, Me-1, Prxa-1 and or by the morphological markers broadness of leaf petiole wing or trifoliolate leaves. Tolerance to the citrus tristeza virus (CTV) was evaluated under nursery and field conditions for several years by the reaction of Valencia orange infected with a severe strain of CTV and grafted onto the hybrids and nucellar clones. Genetic analyses indicated that tolerance was controlled by at least two loci designated here as Az and t interacting in dominant-recessive epistasis. Genotypes Az__ __ __ and __ __ tt were tolerant while azaz T__ was intolerant. The intolerant Azeda was azaz TT, the tolerant rootstocks Sunki and Cravo were Azaz tt and the Trifoliata was Azaz TT. The different degrees of intolerance seen in some hybrids may reflect the inability of segregating modifiers from parental clones to overcome the epistatic interaction that controls the major tolerance reaction.

The influence of citrus rootstocks on the relationship between the mite Brevipalpus phoenicis and citrus leprosis disease

“…On the basis of the results obtained from the percentage map (Fig. ), it was assumed that Sunki rootstock may have increased the tolerance of the ‘Pera’ variety to B. phoenicis mites and even to leprosis disease via some intrinsic characteristics of the rootstock, such as reasonable tolerance to water and salt stresses, and the ability to provide vigorous vegetative growth to the canopy . In addition, Carlos et al reported that Sunki mandarin presents satisfactory resistance to the tristeza, exocortis, psorosis, xyloporosis and citrus blight diseases.…”

Características da laranjeira 'Valência' sobre clones e híbridos de porta-enxertos tolerantes à tristeza

“…Sete diferentes grupos de híbridos (Quadro 1), obtidos por polinizações controladas, identificados por eletroforese de isoenzimas e folhas trifolioladas, enxertados com laranja 'Valência' e transplantados, juntamente com seus genitores para um campo de observação no Centro Avançado de Pesquisa Tecnológica de Agronegócios dos Citros (BORDIGNON et al, 1990;BORDIGNON, 1995;2000;BALLVE et al, 1991;1995; foram previamente investigados quanto a reação ao vírus da tristeza (BORDIGNON et al, 2004) . Em um total de 128 plantas os genitores, exceto a laranja Azeda, se mostraram tolerantes, bem como 396 dos 544 híbridos entre eles.…”