Leaf Isozymes as Genetic Markers in Citrus

Abstract

The genetic control of isozymes from Citrus and its near relatives was determined for three gene/enzyme systems: glutamate oxaloacetate transaminase, phosphoglucose isomerase and phosphoglucose mutase. These enzymes are controlled by four genes having 19 codominant alleles, 12 of which occur in Citrus subg Citrus. Formal genetic studies were carried out with F, biotypes and F1 populations of known origin. When biotypes were grouped into traditionally recognized species to examine genetic affinities within and between species, a remarkable pattern of uniformity of genotype combinations was found within a species, and every species had an unique combination. Because many economically important cultivars produce asexual(nucellar) as well as sexual(zygotic) embryos, a central problem of the breeder is to distinguish these when plants are young, long before fruiting. Isozyme markers can be used with varying degrees of efficiency, depending on the genotypes of the particular parents, to distinguish nucellar seedlings from those of zygotic origin.

Genetic Diversity in Citrus

“…'Ponderosa' was suggested as citron like fruits and notified as monoembryonic with large fruits and hybrid of citron and lemon (Hodgson 1967;Kahn et al, 2001). At the same way, 'Ponderosa' was the most distant cultivar from the other lemons based on leaf isozyme data (Torres et al, 1978). On the other hand, 'Song Panache' lemon have similar-shaped fruit as 'Ponderosa'.…”

“…Low level of genetic variation was found among sour oranges (Uzun, 2009). On the other hand, there was no polymorphism in sour oranges based on leaf isozymes (Torres et al, 1978) and SSR markers (Luro et al, 2000). Torres et al (1978) reported that 'Rangpur' lime is quite different morphologically and genotypically from limes and was listed under C. reticulata.…”

“…On the other hand, there was no polymorphism in sour oranges based on leaf isozymes (Torres et al, 1978) and SSR markers (Luro et al, 2000). Torres et al (1978) reported that 'Rangpur' lime is quite different morphologically and genotypically from limes and was listed under C. reticulata. Nicolosi et al (2000) indicated that 'Rangpur' was a hybrid of citron and mandarin and clustered with the citrons.…”

“…Lemon (C. limon (L.) Burm. f.) was accepted as a species by two important taxonomic systems (Swingle & Reece 1967;Tanaka, 1977), but it has been reported as a hybrid by other studies (Barrett & Rhodes 1976;Torres et al, 1978;Herrero et al, 1996). Besides, lemon was notified as a hybrid of citron and sour orange (C. aurantium L.) in recent studies (Nicolosi et al 2000;Gulsen & Roose 2001).…”

Identificação de espécies de citros mediante polimorfismo enzimático

“…(1978) consideraram as duas e as três bandas pertencentes a um mesmo loco simples. Soost & Torres (1978) consideraram a hipótese de o gene Got-2 ser um loco duplicado com formação de heterodímero intraloco, que foi considerada não definitiva, porém, seguida por Ballvé et ai. (1991).…”