Evaluation of soybean genotypes for resistance to rust disease (Phakopsora pachyrhizi)

Abstract

Pest and disease are one of limiting factor in soybean cultivation in Indonesia. One of the diseases that can reduce soybean production is rust diseases caused by Phakopsora pachyrhizi. The use of resistant varieties can reduce yield losses due to this disease. The aim of this study was to evaluate the resistance of soybean genotypes to rust disease and to study the interaction between agronomic traits with rust disease on soybean genotypes. This study was conducted at a screen house of the Indonesian Legumes and Tuber Crops Research Institute (ILETRI) in Malang, Indonesia from April to July 2015. A total of 10 soybean genotypes consist of eight lines and two varieties (Argomulyo and Grobogan) was evaluated for rust resistance to rust disease. The eight lines tested were a progeny of a cross between offspring of IAC 100 (resistant to rust disease) with high yielding soybean varieties (Argomulyo and Grobogan). The experiment was arranged as randomized completely block design with four replications. Each genotype planted in five plastic pots for each replicate. Three weeks after planting, all plants were inoculated with rust disease. Inoculation was done by spraying a suspension of spores (spore density of 104 spore mL-1) to the surface of leaves. Observations were carried out on rust disease severity based on the method of International Working Group on Soybean Rust rating system, days to flowering, plant height, number of branches, number of fertile nodes, number of pods, and seed weight per plant. The results showed that all genotypes classified as moderately resistant to rust disease. In this study, days to flowering and plant height influence the development of rust disease severity. There are three lines that have seed weight per plant significantly heavier than Argomulyo (4.97 g) and Grobogan (4.30 g), namely K/I100//B63///G-7 (6.55 g), K/I100//B63///G-8 (6.15 g), and I100/B54//A-5 (5.85 g). The high value of the scales of seed weight per plant for the three lines is supported by high-performance plants with a lot of number of fertile nodes and pods. These three soybean genotypes potentially serve as genetic material to develop high yielding soybean varieties and resistant to rust disease.