Morphological, cytological and molecular analysis of interspecific hybrids (Oryza sativa cv IR56 x Oryza brachyantha Acc 101232) of rice.

Date

3-1999

Degree

Bachelor of Science in Biology

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Adelina A. Barrion

Abstract

The possibility of gene transfer from the wild rice Oryza brachyantha Acc 101232 to the cultivated rice Oryza sativa cv IR56 was determined through morphological, cytological and molecular analyses of the interspecific hybrid (0. sativa x 0. brachyantha). Parental materials revealed several differences on morphological characteristics such as height, leaf and panicle features like awning and colors of stigma and pericarp. Interspecific hybrid was intermediate between the two parents in most of the morphological characters observed, although some characters from the wild parent like awning and purple stigma appeared to be dominant. Squash preparations of pollen mother cells (PMC's) fixed in Farmer's solution revealed that both parents possessed 2n=24 chromosomes. Chromosome pairing showing 12 bivalents each during diakinesis and metaphase 1 was normal for both parents, however, the interspecific hybrid showed that out of 50 cells, only a few cells exhibited a maximum of 2 bivalents per cell. During metaphase 1, no bivalents were observed and in some cases the univalents were more than 24 indicating a case of restitution nucleus. The high frequency of unpaired chromosome implies limited homology between the AA genome of 0. sativa and FF genome of 0. brachyantha. The reported short chromosome of 0. brachyantha may also be responsible for the low frequency of chiasma formation during metaphase I. Using VI, the pollens of the interspecific hybrid were determined to be completely sterile due to lack of chromosome pairing. Molecular analyses done through restriction fragment length polymorphism (RFLP) showed that there was polymorphism between 0. brachyantha and 0. sativa. The hybrid showed bands from both parents clearly indicating the true hybrid nature of the F1. In a related experiment, the total genomic DNA of the parents were used as probes. Based on the intensities of signals received upon hydridization of the total genomic DNA of either the cultivated or the wild parent, the divergence of the parental rice species used was established.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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