Selection of Soybean Lines (Glycine max) Tolerant to Drought

Soybean cropping pattern in Indonesia, which follows the pattern of rice-rice-soybean, causing soybean cultivation often encounter the problem of water deficiency due to soybean growing season which falls in the dry season. Soybean varieties tolerant to drought can prevent yield loss due to water deficit. The aim of this research was to identify soybean lines tolerant to drought. A total of 85 soybean lines from F5 generation population were tested in Muneng Experiment Station, Probolinggo district, East Java province from July to September 2013. Six soybean genotypes namely: Dering 1, Tidar, Grobogan, ARG/GCP-335, Tanggamus and SU-17-1014 were used as check. All genetic material planted into five different blocks in the field and arranged as augmented design. Each block contains of 17 different lines and 6 soybean genotypes were planted randomly. Fertilization was given at planting and conducted according to the dosage recommendation, i.e. 100 kg ha⁻¹ of Urea, 75 kg ha⁻¹ of SP36, and 75 kg ha⁻¹ of KCl. Irrigation was only given twice, first at planting time and the latter at the time of flowering with the purpose of conditioning the plant exposed to drought stress during the reproductive phase. The results showed that there were soybean lines with better performance than those of check. Line number 76, 81, and 84 (Tanggamus/Shr-3B-342-207, Tanggamus/Shr-3B-343-208, and Tanggamus/Shr-3B-351-64, respectively) had the number of fertile nodes and the number of pods higher when compared with Dering 1. All soybean lines were classified as ultra early maturing soybean (ranging from 60 to 69 days after planting) and early maturing soybean (ranging from 70 to 73 days after planting). A total of 78 lines (92%) more early maturing when compared with Dering 1, but only 20% (17 lines) more early maturing than those of Tidar. In general, almost all of lines had seed size larger compared to Tidar, but there were only 14 soybean lines with seed size greater than those of Dering 1. However, none of soybean lines are capable of producing seeds exceeds Dering 1 and Tidar.