Screening Some Grain Sorghum (Sorghum bicolor L. Moench) Genotypes for Grain Yield and Plant Tolerance Against Stem Borers Chilopartellus (Swinhoe) andSesamiacretica (Led.)

Abstract

In Sudan, Sorghum (Sorghum bicolor L. Moench) is affected by mainly two lepidopteron stem borers, Chilopartellus andSesamiacretica causing considerable decrease in the yield. A survey was conducted to assess the incidence and distribution of stem borers in Summer sowed sorghum in Khartoum state and to evaluate the status of stem borers infestation on sorghum growing in Khartoum State in eight locations (Al Khadroo, El fakeiHashim, Shambat, Seleet Scheme (north Khartoum) Soba (east Khartoum) El Gezira Islang (north Omdurman), Toti Island (central Khartoum) and Tiba (south Khartoum). The results showed that, the sorghum crop in the study sites was variably infested by both stem borers. The highest infestation of all sites surveyed was recorded in Shambat (60.34%) and the lowest infestation was recorded in Soba (31.7%). There was a significant difference between the number of Chilopartellus and Sesamiacretica in the infested areas. The highest infestation was recorded in Shambat( Chilopartellus65.25% while that Sesamiacretica was 59.99%). The lowest infestation by both agents was found in Soba (Chilopartellus as 33.26%, while that Sesamiacretica was 30.37% ). Two field experiments were conducted under irrigation at the Experimental Farm of the College of Agricultural Studies, Sudan University of Science and Technology, Shambat, Sudan for two cropping seasons (Autumn and Winter) during 2016-17. The experiment was arranged in Randomized Complete Block Design (RCBD) with three replications, to screen the relative resistance/susceptibility of twenty-two genotypes of sorghum against stem borers (Chilopartellus, Sesamiacretica), and to assess for yield and yield components, assess the impact of genetic variability among grain sorghum genotypes, estimates the phenotypic correlation between different characters and to assess the heritable component of the total phenotypic variability using the parameters genetic coefficient of variation and heritability. The plants were subjected to natural infestation by stem borers. Four resistance expressing traits were recorded, i.e. percentage of infested plants, percentage of plants with dead hearts, tunnels length and intensity of damage. The results showed that in Autumn, the maximum level of leave damage was found in F-6 (61.59%), and minimumwas found in G.1.1.4(12.18%), while in Winter, the maximum level of leave damage was found in F-6 (59.15%) and minimum was found in G.1.1.4(15.12%). The percentage of plants with dead hearts formations was higher in more susceptible genotypes than least susceptible genotypes. Results showed that, G.1.1.4 was found to be the most resistant to all studied types of damage The Maximum occurrences of dead hearts were recorded in genotypes F- 6(4.99%, 4.21%) in Autumn and Winter respectively. The higher and lower Value of tunnels length ranged between F-6 (5.32cm) to Tabat (2.38) in Autumn, and F-6(5.38cm) to G.1.1.16 (2.67cm) in Winter season. The following growth and yield traits were measured: plant height, stem diameter, number of leaves /plant, leaf area, days to 50% flowering, days to physiological maturity, panicle length, panicle width, panicle exertion,1000 seeds weight and grain yield ton/ha. The results showed that there were significant differences among the 22 sorghum genotypes for some growth yield and stem borer’s infestation in both seasons. Genotypes (F- 6) scored the highest grain yields (1.34t/ha), (1.28 t/ha) in Autumn and Winter respectively, in spite of high leave damage 61.59%, 59.15% and high tunnels length 5.32cm, 5.38cm. This result illustrates the ability of the genotypes to produce high yield coupled with their tolerance to stem borer infestation. Genotype F-6 could be of advantage for any future sorghum breeding program. All genotypes gave higher yields in Autumn than in Winter. This can attributed to the favorable environmental conditions during the rainy season coupled by the lighter infestation of the stem borers. Genotypes F-5, F-15 gave highest value 197cm, 195 cm in Autumn and Winter respectively. The earliest flowering genotype was Arfagadmk (64.3days and 59.6days) in both Autumn and Winter seasonrespectively. For 1000-grain weight genotype G.1.1.4 (46.1g and 45.0g) in Autumn and Winter respectively. The phenotypic and genotypic variances, phenotypic (PCV) and genotypic (GCV) coefficient of variation, heritability (h2), phenotypic and genotypic correlation between different characters were calculated. There was a wide phenotypic variation among the genotypes in most of the characters studied. The genotypic component of the phenotypic variance was consistently higher than the heritability broad sense estimates that ranged from (95% - 41%). High heritability was reflected in this study among the following growth characters: plant height (0.95-0.88), days to maturity (0.76-0.83), days to 50% flowering (0.73-0.84) and leaf area (0.67-0.92) for both seasons. Genotypic coefficient of variation (GCV) was maximumin Leaf area (2313.70 and 4665.9) plant height (999.63 and 1162.66) for both seasons and it was not different than phenotypic coefficient of variation (PCV). It showed maximum value in leaf area (3444.38 and 5045.60) and plant height (1047.93 and 1327.46) for both seasons.This result indicated that these traits were affected by environmental fluctuations. The high values of (GCV) and (PCV) suggest the possibility of utilizing environmental effects through direct selection for these traits. Estimates of phenotypic correlations among different characters in the two seasons were variable from one season to another. Grain yield ton/ha had strong positive phenotypic correlation with some of the morphological characteristics and the susceptibility of the plant to stem borers.This indicates that the strong inherent associations between different traits are different under the different environments and hence the phenotypic correlations are dependent on environmental conditions.