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University of Agriculture, Faisalabad (2015)

Studies on metaxenial effect and use of molecular approaches for detection of hybrids, genetic diversity and sex in date palm (Phoenix dactylifera L.)


Titre : Studies on metaxenial effect and use of molecular approaches for detection of hybrids, genetic diversity and sex in date palm (Phoenix dactylifera L.)

Auteur : Maryam

Université de soutenance : University of Agriculture, Faisalabad

Grade : Doctor of Philosophy (PhD) 2015

Résumé partiel
Date palm (Phoenix dactylifera L.) has been an important crop in the desert regions of Asia and North Africa for centuries know adopted in many countries. Alexander the great and Arab conquerors introduced date fruit in Indo-Pak subcontinent after that date extended as a food item. Date palm is among the oldest cultivated plants in history of mankind, being used as food for 6000 years. Date is a world agricultural industry with total production of 7.5 million metric tonnes (MT) of fruit and Pakistan contribution is 10.34 metric tonnes. Date palm (2n=36) is dioecious monocotyledonous belonging to Arecaceae family. Fertilization and fruit set are consequences of pollination as there is an interesting but uncommon effect known as metaxenia, the direct influence of pollen on maternal tissues of date palm. Pollen not only control the fruit set, size of fruits and seeds but also effect the time of ripening. As pollen grains caused the great diversity and variations in size, quality and ripening time so 9 different pollen sources were selected to study the differential behaviour of pollen parents on fruit characteristics of two female cultivars i.e Hillawi and Khadrawy. Fruit was harvested at Khalal stage from controlled pollinated treatments and pysicochemical analysis was carried out to study the metaxenial effect of different pollen. Physical characters including ripening time, bunch weight, fruit length, fruit width, fruit area, pulp weight, seed weight and biochemical characters, total sugars, DPPH, ascorbic acid, total phenolic contents, total soluble solids, total proteins, sucrose, glucose, fructose, and enzymatic activities (peroxidase, catalaze, superoxidase ans protease) were highly variables. Data regarding all physicochemical characters was analyzed statistically using the two factor factorial in Randomized Complete Block Design (RCBD) that showed the significant differences in all variables. Duncan multiple range test was used to discrete the means (using the statistica 9.1) revealed that different pollen sources respond variably. Among 9 pollen sources M8 ( 32) was superior because it was positively associated with most of the variables. Fruits developed from M8 pollination were prominent with high bunch weight more sweetly in taste (high total sugars), good fruit area, enriched with protein, reduced seed weight, high antioxidant and enzymatic activity and reduced ripening time. M7 (collected from Uni campus) retained highest capability for ascorbic acid, reduced ripening time, good fruit length and width, reduced seed weight. For more positive correlation of pollen parents M8 was followed by M7, M3, M5 and M4. Strong positive correlation was found among most of 16 the traits. All the new combinations developed from pollinating the 2 date palm cultivars with 9 pollen sources were categorized by principle component analysis. The morphological and biochemical dendrogram generated from Wards method can distinguished these combinations into 3 and 2 clusters for cultivar Hillawi and Khadrawy respectively. Our results showed that physicochemical traits (using XLSTAT software) were very appropriate for studying the metaxenail effect that can be used for further breeding targets as economically very important regarding yield and quality. For hybrid identification 12 Simple Sequence Repeats were used to identify the true hybrid of date palm developed from the seeds, resulted from the controlled pollination from their respective parents. Main objective of this study was to identify the true hybrids respective to their parents to carry out the further breeding programmes. Out of 12, only 6 SSR primers clearly produced the SSR amplification with the size ranging from 125 to 500 bp. These six microsatellite primers resulted in 66 microsatellite loci with a mean of 11 loci per primer. Total 6 primers identified the true to type as well as ambiguous hybrids. Primer mpdCIR-10 identified the maximum no of true hybrids 13 (81.25%) out of 16 while 3 ambiguous hybrids (18.75%). In comparison, DP159 detected only 10 (62.5%) true hybrids and maximum ambiguous hybrids i.e 6 (37.5%). 75% true hybrids were determined with primer mpdCIR16 and mpdCIR25 followed by the mpdCIR15 and mpdCIR93 (68.75%). 12 microsatellite primers were used with 30 date palm samples which showed that microsatellites were highly polymorphic, having a great number of alleles.

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Page publiée le 17 mai 2019