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Characteristics of Three Cotton Varieties and Their Impact on Feeding and Growth of Cotton Armyworm

Md Ruhul Amin
Department of Entomology, Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh

Dil Afrose Tithi
Department of Entomology, Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh

Yong Jung Kwon
Department of Agricultural Biology, Kyungpook National University, Daegu, Korea

Abstract/ Executive Summary:

This study investigated morphological and biochemical characteristics of CB9, CB10 and SR05 cotton varieties and observed their effect on feeding and growth of cotton armyworm Spodoptera litura. Morphological characters of plant architecture, branching, color, hairiness, trichome density and boll size indicated that CB9 is a bushy, well developed, branched, light bronze colored and hairy variety with number of trichomes 193/cm² and boll weight 5.5–6.0 g/boll. Both CB9 and CB10 bear normal leaves and spherical bolls whereas SR05 has well-ventilated branching, okra shaped and ventrally arranged light bronze colored leaves and oval bolls ranging 4.0–4.5 g/boll. Biochemical analysis indicated significant differences in starch and protein contents, which range 11.4–21.3 and 17.5–30.6%, respectively. The lowest percentages of starch and protein were found in SR05 and CB9, respectively. Cotton varieties showed significant effects on second, third, fourth and fifth instar larval weight and they attained the highest weights (22.7, 133.8, 168.2 and 1190.2 mg, respectively) when fed SR05. Larvae and moths fed SR05 also showed the significantly highest cocoon, exuviae, and adult male and female weights (434.5, 19.2, 161.3 and 232.4 mg, respectively). The cotton armyworm showed the significantly highest growth index (1.5) as well as lowest feeding index (0.05) on SR05. Results of this study indicated that SR05 is suitable for larval feeding and development, and suggest that this variety is least suitable for cotton growers in areas where S. litura is a major pest.

Keywords: Cotton armyworm, characteristics, cotton, variety, weight

Location: Field of the Regional Cotton Research Station, Dinajpur, Bangladesh

Start Date: 00-00-2008

End Date: 00-00-2009

Program Area: Variety and Species

Commodity: Cotton

Objectives:

To investigate the morphological and biochemical characteristics of CB9, CB10 and SR05 cotton varieties and
To observe their effect on feeding and growth of cotton armyworm Spodoptera litura.

Methodology:

Experimental field and cultivation of cotton varieties: The cotton varieties CB9, CB10 and SR05 were cultivated in the field of the Regional Cotton Research Station, Dinajpur, Bangladesh (25°13′N, 88°23′E). The soil was sandy loam with pH 5.2. Seeds of CB9, CB10 and SR05 were sown in plots 5.4 m X 5.0 m on 3 August 2008 with a spacing 45 cm from plant to plant and 90 cm from row to row. Intercultural operations such as mulching, weeding and irrigation were done whenever necessary and fertilizers were applied according to the recommended doses of the Cotton Development Board of Bangladesh. Observation of morphological characteristics: Morphological characteristics of plant architecture, branching, stem color and hairiness; leaf shape, color, hairiness and bract shape; nectar gland, flower color, boll shape and size, and boll bearing (number/plant) were observed by eye. The number of leaf trichomes (number/cm²) was counted using a 200 X optical microscope. Biochemical analysis: Determination of starch: The percentage of starch content in the leaves, flowers and fruits of CB9, CB10 and SR05 was determined and the mean value of each variety was calculated. Estimation of starch was carried out by the method. The sample was measured at 630 nm in a spectrophotometer and converted to the amount of glucose with a standard curve prepared using known concentrations of glucose. The glucose concentration was multiplied by 0.9 to calculate the starch content of the plant. Determination of protein: The percentage of protein of the varieties was determined from their leaves, flowers and fruits and the mean value of each variety was calculated. The conventional Kjeldahl method was adopted for nitrogen determination. The percentage N of the sample was multiplied by 6.25 to obtain the percentage protein content. Collection and rearing insects: Adult male and female moths were collected from the field of the Regional Cotton Research Station, Dinajpur, Bangladesh and kept in pairs in Petri dishes (9.0 cm X 1.5 cm) for mating. The Petri dishes with moths were kept in the laboratory at 25 2°C, 60 5% relative humidity (RH) under conditions of 12 h light : 12 h dark (LD 12:12). Every morning fresh cotton flowers of one of CB9, CB10 or SR05 were supplied to the Petri dishes for food. After 3 days, the male moths were removed from the Petri dishes and the females were transferred to jars (26.5 cm X 13.5 cm) for oviposition. Leaves and flowers of the respective variety were supplied into the jars. Every morning the jars were cleaned and monitored to observe the egg mass. Weight measurements: Wet weight of different larval instars, cocoons, and adult males and females were measured by a Mettler digital balance. Growth index: Growth index (% adult eclosion/total development period) was calculated by the formula. Feeding index: Feeding index (pupal weight/total weight of leaf tissue consumed) was adopted by the method. Data analysis: Data were analyzed by analysis of variance and the mean values were separated by Duncan’s multiple range test (DMRT). All the analysis were performed using PASW Statistics 18 (SPSS Inc., Chicago, Illinois, USA).

Source of Information: Entomological Research 41 151–156, 2011

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

SR05 is a well ventilated, green colored, slight hairy and low trichome content variety that has a lower percentage of starch and a substantial amount of protein, which might be the reason for better development of the pest.

Knowledge Management: Journal