M. U. AHMED
Ph.D. Fellow
Department of Botany, Jahangirnagar University, Savar, Dhaka and
Principal Scientific Officer, Plant Pathology Division, BARI, Joydebpur, Gazipur 1701
ABUL KHAIR
Professor
Department of Botany, Jahangirnagar University, Savar, Dhaka
I. H. MIAN
Professor
Department of Plant Pathology, BSMRAU, Gazipur 1706, Bangladesh
Screening, Wheat germplasm, Seedling diseases
Variety and Species
A total of 15 germplasm of wheat, namely BAW-1033, BAW-1045, BAW1056, BAW-1061, BAW-1064, BAW-1004, BAW-1008, BAW-1027, BAW1035, Sonalika, Gourob, Protiva, Shatabdi, Sourov and Kanchan (check) were evaluated under pot culture conditions for their susceptibility to different seedling diseases recorded during the survey in wheat fields. The experiment was started with 15 germplasrn of wheat during 2003-2004 growing season and was repeated during 2004-2005 crop seasons using nine germplasm. The earthen pots of 30 cm diameter were filled with sandy loam soil. Before potting, the soil was steam sterilized and mixed with well decomposed cowdung @ 10 t/ha and Urea, TSP. MP, and Gypsum @ 220, 132, 68 and 125 kg/ ha, respectively (Ahmed and Meisner, 1996). Inocula of S. rolfsii, B. sorokiniana, and F. oxysporum were prepared on barley grains. The barley grains were soaked in water for 24 hours, excess water was decanted from the grains and poured into 500 ml conical flasks (about 2/3rd of the flask). The mouth of conical flask was wrapped with aluminum foil and autoclaved for sterilization at 121°C for 15 minutes at 0.7kg/cm2 pressure. After proper cooling, the sterilized barley grains were inoculated with 10 mycelial blocks (0.5 mm diameter) cut from 5 days old PDA culture in petridishes. Inocula of R. solani and P. aphanidermatum were prepared in a mixture of sand : maize meal: water. For multiplication of R. solani, the mixture composed of 20g maize meal: 980g sand:250 ml sterilized water and for P. aphanidermatum maize meal: sand:water were mixed at 3:1:1 ratio. The mixtures were sterilized in autoclave at 121°C for 15 minutes at 0.7kg/cm2 , poured into conical flasks and inoculated with 5 days old mycelial blocks of the fungi. The inoculated flasks were kept under room temperature for 3 weeks for growth of the fungus. For uniform colonization, the flasks were shaken with hand every alternate day. The colonized barley grains were air dried on paper trays at room temperature (28°C ± 2 °C) and stored at 4°C in a refrigerator for future use. The pot soil was inoculated with S. rolfsii, B. sorokiniana, F. oxysporum, P. aphanidermatum and R. solani before 7 days of sowing. The inoculum was mixed at the rate of 100 g/kg of soil. Steam sterilized pot soil was mixed thoroughly with the inocula. After inoculation, the pot soil was covered with sterile sand to ensure the viability of inoculum. Then water the pots from the top to facilitate rapid spread of the inoculum. In case of Pythium, soil was saturated with water before and after the inoculum was added. After inoculation, pots were incubated for 72 hours, first at a temperature suitable for sporangia formation and then suitable for disease development. To avoid the pre- emergence damping off, the inoculum was placed 2-3 cm below the seed (Dingra and Sinclair, 1995). The pots were arranged on the pot yard of Plant Pathology Division, BARI, Gazipur following completely randomized design. Three pots (replications) were used for each germplasm. Equal number of 25 seeds were sown in each pot. After emergence, watering and mulching were done as and when necessary to maintain appropriate soil condition for proper growth of wheat seedlings. After emergence, data on total number of healthy and diseased seedlings in each pot were recorded at every 3 days and continued upto 35 days. Finally percent of diseased seedling was calculated based on total number of seedlings per pot. The wheat germplasm were graded according to their reaction to different seedling diseases following a standard grading scale (Anon., 1985). where Resistant (R) = 0-5%, Moderately resistant (MR)= 6-10%, Moderately susceptible (MS)= 11- 20%, Susceptible (S) 21-30% seedlings were diseased. Germplasm showing 31% or more seedlings diseased were graded as Highly Susceptible (HS). Vigour index (VI) of seedling was determined by using a standard formula (Baki and Anderson, 1972) as followes: Vigour Index = (mean root length+ mean shoot length) x percent emergence. All data were analyzed statistically following SPSS programme.
Bangladesh J. Agril. Res. 34(4) : 673-681, December 2009, ISSN 0258-7122
Journal