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MORPHOLOGICAL AND GENETIC CHARACTERIZATION OF CITRUS POLYPLOIDS

Fatima, Bilquees (2004) MORPHOLOGICAL AND GENETIC CHARACTERIZATION OF CITRUS POLYPLOIDS. PhD thesis, University of Agriculture, Faisalabad.

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Abstract

Although Citrus enjoys the premier position among all fruits in Pakistan, there are several problems that occur including high number of seeds, lack of genetic diversity and a number of diseases and insect pests etc. Genetic characterization of polyploidy could help to improve Citrus both through breeding and biotechnological approaches. Therefore, Citrus polyploidy of both nutural and induced origin were subjected to morphological and genetic characterization. Seed number and size was found to be cultivar dependent. Among the four cultivars explored, Kinnow showed the highest numbers seeds per berry followed by Musambi, Succari and Feutrell’s Early. Different plant sides have not shown any significant impact on the development of seeds. Germination behavioral studies revealed that sweet orange cultivars Musambi and Succari had greater root and shoot length in vitro than mandarins for both underdeveloped and shriveled seeds. Chromosomal analysis revealed that the highest percentage of naturally occurring triploids was found in kinnow (9.95%) while percentage of tetraploids was the highest in Succari and Kinnow (6.05%). The stomatal size and number of chloroplasts were found directly proportional to the ploidy while number stomata was inversely proportionate to ploidy. Colchicine treatment in vivo also showed was significant increase in the number of chloroplasts in colchiploids. The morphological characterization of polyploids obtained from open pollinated Citrus seeds, colchicines induced polyploids and the interploid hybrids of diploid and tetraploid Kinnow showed signinficantly better root and shoot length (cm) in the ploids of sweet orange cultivars than the Mandarins. Spontaneous Kinnow triploids had shorter root and shoot length while spontaneous Musambi tetraploids were found to have large root and shoot length. The foliage studies and the leaf analysis of the ploids depicted a direct proportion to the ploidy level as various leaf parameters increased with increase in the ploidy level. Regarding recovery of spontaneous polyploids, Citrus cultivars Kinnow and Musambi were high in spontaneous triploids while Kinnow and Succari were high in tetraploids. Colchicine application significantly delayed the bud sprouting, decreased sprouting percentage and shoots length and showed about two fold increases in the leaf lamina length and width. The genetic analysis of the Citrus polyploids through SSR molecular markers confirmed the genetic variability of the morphologically distinct spontaneous and colchicines induced ploids; and interploid hybrids. The methodology of using SSR loci genotyping with morphological selection and cytological screening of putative polypoids appeared as a much improved strategy in the identification of zygotics, nucellars, hybrids as well as polyploids at the seedling stage. Consistency in such studies will help to develop a Citrus germplasm bank by saving cost, reducing time and selecting a wide range of genetically characterized Citrus Polploids for diversification of production base in Pakistan.

Item Type:Thesis (PhD)
Uncontrolled Keywords:citrus polyploids, germination, pollination, genetic characterization, polyploidy, kinnow, musambi, succari, feutrell, interploid, tetraploid
Subjects:Agriculture & Veterinary Sciences(a) > Agriculture(a1) > Forestry, horticulture(a1.3)
ID Code:648
Deposited By:Mr. Muhammad Asif
Deposited On:14 Sep 2006
Last Modified:04 Oct 2007 21:02

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