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  • Author or Editor: Chemda Degani x
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Abstract

Cultivars of fruit trees are vegetatively propagated in order to ensure a uniform crop with fruit of consistent quality. Unequivocal identification of the propagation material is essential for assuring the desired quality.

Open Access

Abstract

Using a malate dehydrogenase isozyme system, it was possible to identify the pollen donor parent in progenies of avocado (Persea americana Mill.) obtained by enclosing 2 cultivars of complementary flower type in a screenhouse with a beehive. The observed percentage of cross-pollination ranged from 7% to 92%. Isozymes are demonstrated to be a practical way of identifying hybrids.

Open Access

Abstract

Outcrossing rate in a solid block of ‘Hass’ avocado (Persea americana Mill) was determined using the isozyme systems of malate dehydrogenase (MDH) (EC 1.1.1.37), leucine aminopeptidase (LAP) (EC 3.4.11.1), and triosephosphate isomerase (TPI) (EC 5.3.1.1), for which evidence concerning the genetic control of the latter is presented. Almost all ‘Hass’ mature fruits were found to have resulted from cross-pollination. Among the potential pollen donors—‘Hass’, ‘Ettinger’, and ‘Reed’—‘Ettinger’ excelled, producing almost all of the hybrid fruits.

Open Access

Abstract

Outcrossing rates in ‘Hass’ and Fuerte’ avocado (Persea americana Mill.) blocks were determined during fruit development using the isozyme systems of malate dehydrogenase (MDH, EC 1.1.1.37), leucine aminopeptidase (LAP, EC 3.4.11.1), and triosephosphate isomerase (TPI, EC 5.3.1.1) as genetic markers. Abscission of avocado fruitlets was selective and was greatly influenced by the pollen parent. Thus, in ‘Hass’ trees subjected to crosspollination by ‘Ettinger’ and ‘Fuerte’, the population of ‘Hass’ fruitlets 1 month after fruit set consisted mainly of ‘Hass’ selfs; however, during fruit development, the rate of ‘Hass’ selfs decreased and the rate of ‘Hass’ hybrid fruitlets produced by ‘Ettinger’ and ‘Fuerte’ increased. By the end of fruit abscission, the surviving mature ‘Hass’ fruits were mostly ‘Ettinger’ hybrids. The ‘Hass’ fruit yield was found to correlate significantly with the rate of outcrossing with ‘Ettinger’. When ‘Ettinger’ served as a pollen parent for ‘Fuerte’, the outcrossing rate in trees adjacent to ‘Ettinger’ was about 40%, which shows that cross-pollination among avocado cultivars of the same flowering group can be substantial at close proximity. The outcrossing rate in ‘Fuerte’ diminished with increasing distance from ‘Ettinger’, but no effect on yield was observed.

Open Access

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.

Free access

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.

Free access

Abstract

Evidence is presented suggesting that genetic selection could be an important factor in avocado fruitlet abscission. ‘Ettinger’ embryos (Persea americana Mill.) at different stages of fruit development were classified according to their leucine aminopeptidase (LAP) electrophoretic pattern in the Lap-2 locus. Analysis of several fruitlet populations showed significant deviations from the expected Mendelian ratio. The genotypic ratios at the different stages indicate genetic selection during fruitlet abscission.

Open Access

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.

Free access

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.

Free access

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.

Free access