Theses and Dissertations


Title: RESPONSE AND CORRELATED RESPONSE TO SELECTION OF CHANNEL CATFISH, ICTALURUS PUNCTATUS, FOR RESISTANCE TO EDWARDSIELLA ICTALURI, FLEXIBACTER COLUMNARIS, LOW LEVELS OF DISSOLVED OXYGEN, TOXIC LEVELS OF NITRITE

Name: Waters, Phillip Lynch Jr.

Degree: MS

Chair: Rex A. Dunham

Resides:

University: Auburn University

Location: Auburn, Alabama

Date: 2001

Pages: 65

Keywords: Channel catfish,genetic selection,disease resistance,resistance to dissolved oxygen,resistance to high nitrite

Abstract:

Four challenges were conducted to determine resistance to Flexibacter columnaris, Edwardsiella ictaluri (ESC), low dissolved oxygen (<0.6 ppm), and lethal levels of nitrite in different lines of channel catfish, Ictalurus punctatus. Response and correlated response to selection, mean survival, percent gain, and realized heritability were calculated for channel catfish within each challenge. Mean survival from columnaris epizootics (challenge) in 1999 and 2000 was 57.3%. ESC mean survival ranged from 0%- 77.5%, with a grand mean of 39.0%. Differences were found (chi square) between observed and expected survival of the lines of channel catfish challenged by Flexibacter columnaris (P < 0.001) and Edwardsiella ictaluri (P < 0.001). Response to selection for resistance to disease was calculated as percent gain and ranged from -2.9% to 128% for columnaris and -97.0% to 26.0% for ESC. Correlated response to selection ranged from -40.8% to 32% for columnaris and -18.7% to 93.8% for ESC. Channel catfish lines challenged with low levels of dissolved oxygen were significantly different (P = 0.0001, (a = 0.05). Mean survival of the 1999 and 2000 dissolved oxygen challenges ranged from 30.5% to 89%, with a grand mean of 58.5%. Differences were observed between the selected lines 8L81L (P=0.004, a = 0.05), 43R (P = 0.034, (a = 0.05), and 2L21L (P = 0.03, (x = 0.05) and their controls 8L, 4R, and 2L, respectively. Response to selection, recorded as percent gain, ranged from -53.0% to 122.0%. One correlated response to selection was calculated to be 182% gain. Channel catfish lines challenged for tolerance to lethal levels of nitrite were different (P = 0.017, a = 0.05). Mean survival ranged from 17.4% to 83.8%, with a grand mean survival from l999 and 2000 of 47.4%. Differences were observed between the selected lines 83L8L (P = 0.05, a = 0.05), 82L83L (P = 0.007, (a = 0.05), and 41R (P = 0.02, (a = 0.05), and their respective control lines. Response to selection, recorded as percent gain ranged from - 24.4% to 193%. Correlated response to selection ranged from -67.5% to 219.0%. A positive response was obtained for 3 of 5, 2 of 3, 2 of 3, and 1 of 2 lines to selection for low dissolved oxygen, high nitrite, resistance to columnaris, and resistance ESC, respectively. A positive correlated response was obtained for 1 of 1, 2 of 3, 1 of 5, and 2 of 3 lines to selection for low dissolved oxygen, high nitrite, resistance to columnaris, and resistance to ESC, respectively. In general selection and indirect selection for tolerance of low water quality was similar to selection and indirect selection for disease resistance in success. Direct selection for disease resistance was slightly more successful than indirect selection for disease resistance.

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