Research Projects
Reproduction Control Research

Subcontract No. RD010A-02

Staff

University of Oklahoma, Norman, Oklahoma

William Shelton	US Principal Investigator, Project Leader
William Baker	Research Assistant (June through August 2000)
Robert Raymond	Research Assistant

Background

Limited knowledge of the reproductive physiology and breeding of culture species was identified as one of the key constraints to aquaculture in the Continuation Plan 1996–2001. Specifically, effective and practical control of reproduction is the major constraint in tilapia culture. Inter- and intraspecific breeding programs can result in populations with highly skewed sex ratios but often give inconsistent results. Interspecific crosses have not proven to be practical due to difficulties in maintaining the parent species integrity.

Intraspecific breeding programs have been developed to exploit the sex inheritance mechanism in Nile tilapia, Oreochromis niloticus. The androgenetic approach to developing YY males simplifies the identification of YY males as all males produced should be of the YY genotype. Proposed Ninth Work Plan research will search for a phenotypic marker to further simplify identification of YY males and continues efforts to develop androgenesis techniques for Nile tilapia of the Egyptian and Ghanaian strains.

Work Plan Research

This subcontract was awarded funding to conduct the following Ninth Work Plan investigation:

• Monosex tilapia production through androgenesis/9RCR7. An abstract was submitted for this investigation.

Note: The schedule and methods for 9RCR7 have been modified. Please see Appendix 5, "Completion dates for Work Plan Studies," for revised schedule information. The revised methods will appear in the Addendum to the Ninth Work Plan.

Conferences

PD/A CRSP Annual Meeting at New Orleans, Louisiana, 31 January–2 February 2000. (Shelton)
Aquaculture America 2000 at New Orleans, Louisiana, 2–5 February 2000. (Shelton)

Monosex Tilapia Production through Androgenesis

Ninth Work Plan, Reproduction Control Research 7 (9RCR7)
Abstract

William L. Shelton
University of Oklahoma
Norman, Oklahoma, USA

Abstract

A phenotypic marker in chromosome manipulation investigations is vital to interpreting induction results. During earlier studies on androgenesis in tilapias, males of the homozygous recessive color mutation (blond) in Nile tilapia (Oreochromis niloticus; Egyptian strain, Lake Manzala) were used as an induction control to verify that progeny carried only the paternal genome. Control crosses between blond males and normal colored females (Ghana strain) produced viable progeny, but survival of androgenotes (paternal, blond) was extremely low. Severity of the induction treatment and inbreeding of the blond mutant were considered possible factors. An alternative approach is being tested which involves another color mutation as the phenotypic marker. Red tilapia also originated from the same population (Egyptian strain, Lake Manzala), but the color mutation is a dominant trait. Thus, red females and Ghana males are being used, since the relatively unselected paternal genome of the Ghana strain might be hardier. However, the inheritance of the color and the pigment development pattern must be verified through progeny testing. The color pattern of red x red and red x Ghana is now being examined. Broodstock of these phenotypes and in these combinations have been pair spawned during the latter part of this reporting period.