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Chemda Degani, Ruth El-Batsri and Shmuel Gazit

Forty-one (Mangifera indica L.) cultivars were characterized electrophoretically using the isozyme systems aconitase, isocitrate dehydrogenase, leucine aminopeptidase, phosphoglucose isomerase, phosphoglucomutase, and triosephosphate isomerase. The outcross origin of some of the mango cultivars was supported by the isozymic banding patterns. Reported parentage of some other cultivars was not consistent with their isozymic banding patterns.

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Chemda Degani, Ruth El-Batsri, Raphael A. Stern and Shmuel Gazit

Fruits produced in two commercial lychee (litchi chinensis Sonn.) orchards consisting of adjacent blocks of `Floridian' and `Mauritius' were analyzed for pollen parentage by phosphoglucose isomerase (PGI) isozyme system. 'Mauritius' and `Floridian' were found to possess distinguishable homozygous isozyme phenotypes in PGI, thus allowing the unequivocal identification of their progenies as originating from self- or cross-pollination. The rates of hybrids produced in the two orchards were 69% and 87% for `Floridian' and 17% and 65% for `Mauritius'. In both cvs a significant correlation was found between pollen parent and the weights of fruits and seeds. Fruits originating from cross-pollination were heavier and contained heavier seeds than selfed fruits. The most pronounced effect of the pollen parent on seed weight was found in `Floridian, which appears to exhibit inbreeding depression.

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Chemda Degani, Menashe Cohen, Ruth El-Batsri and Shmuel Gazit

Leaf phosphoglucose isomerase (PGI) isozymes from 139 cultivars and seedlings of mango (Mangifera indica L.) were analyzed by starch gel electrophoresis. Six distinct banding patterns of PGI-2 consisting of single- and triple-banded phenotypes were detected. The genetic control of PGI-2 isozymes were inferred from segregating progenies of self-pollinated parent cultivars having triple-banded phenotypes. Comparison of the banding patterns of PGI-2 isozymes extracted from the pollen and the leaf of the same heterozygous cultivar demonstrates the allelism of the Pgi-2 locus.

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Uri Lavi, Emanuel Lahav, Chemda Degani and Shmuel Gazit

Avocado (Persea americana Mill.) progeny that originated from 11 crosses (both self-pollinations and crosses between cultivars) were evaluated for the length of their juvenile period. Time to first flowering, “flowering age,” and time to first fruit production, “fruiting age,” were recorded for each progeny. The mean values for both ages, the sd, and the progeny distribution were calculated. Significant statistical differences in flowering age and fruiting age between various progeny populations were detected. No differences were detected between self-pollinated plants and crosses. The time until first flowering was found to be the limiting factor in evaluation of seedlings.

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Uri Lavi, Emanuel Lahav, Chemda Degani, Shmuel Gazit and Jossi Hillel

Genetic variance components for avocado (Persea americana Mill.) traits were estimated to improve avocado breeding efficiency. The additive and nonadditive genetic variance components were calculated from the variances between and within crosses. In all nine traits examined, i.e.-anise scent, fruit density, flowering intensity, fruit weight, harvest duration, inflorescence length, seed size, softening time, and tree size-a significant nonadditive genetic variance was detected. Additive genetic variance in all traits was lower and nonsignificant. The existence of major nonadditive variance was indicated also by narrow-sense and broad-sense heritability values estimated for each trait. Therefore, parental selection should not be based solely on cultivar performance. Crosses between parents of medium and perhaps even low performance should also be included in the breeding program.

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Chemda Degani, Anat Goldring, Itzhak Adato, Ruth El-Batsri and Shmuel Gazit

The effects of various pollen parents on outcrossing rates, yield, and fruit and seed weights were studied in a `Fuerte' avocado (Persea americana Mill.). Isozyme analysis was used to identify the pollen parent of mature fruits. Cotyledons were assayed for five polymorphic enzyme systems: alcohol dehydrogenase, leucine aminopeptidase, malate dehydrogenase, phosphoglucomutase, and triosephosphate isomerase. When sampling of fruits was done to a height of 2 m, percent of hybrids produced by `Teague' and `Topa-Topa' pollenizers was in the range of 30% to 40%. With `Teague' as the pollenizer, `Fuerte' yield increased by 30% in trees adjacent to the pollenizer. With `Tops-Tops' as pollenizer, the yield was increased by 40% for trees adjacent to and at a distance from the pollenizer. `Ettinger' trees planted at a distance of 30 to 50 m from `Fuerte' were found to be the pollen parent of 2% to 14% of the progeny, thus supporting our previous conclusion regarding the high potency of `Ettinger' as a pollen parent. `Tops-Tops', `Teague', and `Ettinger' significantly increased fruit and seed weights of crossed compared with selfed `Fuerte' fruits.

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Chemda Degani, Jiusheng Deng, Avigdor Beiles, Ruth El-Batsri, Moshe Goren and Shmuel Gazit

There is widespread confusion and uncertainty concerning the identity of lychee cultivars: the same cultivar may be known under different names and different cultivars may appear under the same name. In the present study, the potential of intersimple sequence repeat (ISSR) for the identification of 66 lychee cultivars and accessions and a determination of their genetic relationships was evaluated, using 32 primers containing different simple sequence repeat motifs. Of the 194 bands produced, 124 (64%) were polymorphic. A set of six ISSR primers was sufficient to distinguish all cultivars and accessions. Thus, cultivars which are morphologically very similar and have identical isozyme profiles can be distinguished by ISSR analysis. However, seven pairs of accessions, each considered to be the same cultivar, were found to be identical by ISSR analysis. Nei and Li band-sharing distances and Nei genetic distances were calculated among the cultivars and two similarity dendrograms were generated using the neighbor-joining algorithm. Results showed that the ISSR technique is a valuable tool for identification of lychee cultivars and analysis of their genetic relationships.