Resistance to Soybean Aphid in Early Maturing Soybean Germplasm

Abstract

yellow, and even drop. Other symptoms of direct feeding damage include plant stunting, poor pod fill, reduced Since 2000, the soybean aphid (Aphis glycines Matsumura) has pod and seed counts, smaller seed size, and nutrient become a major pest of soybean [Glycine max (L.) Merr.] in North America. In the USA, there are currently no commercial soybean deficiencies resulting in overall yield and quality reduccultivars with aphid resistance and there are no reported resistance tion (DiFonzo and Hines, 2002). Significant yield loss sources in early maturing soybean germplasm. The objectives of this (8-25%) occurs when the soybean plants are heavily study were to identify sources and types of resistance to soybean aphid infested by the aphid during the early reproductive stage from early maturing soybean germplasm. Over a 2-yr period, 2147 (DiFonzo and Hines, 2002). Honeydew, a sticky subsoybean accessions from maturity group (MG) 0 to III, originally stance excreted by soybean aphids onto the leaves, leads from northern China, were evaluated for aphid resistance in a greento the development of sooty mold, which affects photohouse and in field cages. The plants were hand-inoculated and aphid synthesis and results in yield loss (Baute, 2004). During populations were evaluated 10 d after inoculation. A damage index the feeding process, soybean aphids are capable of trans-(0-100%) was calculated for each accession. After 2 yr of evaluation mitting viruses including Alfalfa mosaic virus, Soybean and confirmation in choice tests, four MG III accessions from Shandong province, PI 567543C, PI 567597C, PI 567541B, and PI 567598B, mosaic virus, and Bean yellow mosaic virus. These viwere found to be resistant to the soybean aphid. Two of these acces-ruses commonly occur together and form a disease comsions, PI 567541B and PI 567598B, possessed antibiosis resistance,plex that leads to plant stunting, leaf distortion and preventing the aphids from reproducing on the plants in a no-choice mottling, reduced pod numbers, and seed discoloration study. PI 567543C and PI 567597C possessed antixenosis resistance.

Mapping soybean aphid resistance genes in PI 567598B

“…It is also possible that the two genes discovered in this study are allelic to Rag1 or Rag3, or different genes, but tightly linked to Rag1 or Rag3. Rag1 in Dowling can be overcome by the Michigan aphids and Rag3 in PI 567543C did not provide antibiosis resistance (Mensah et al 2005). PI 567598B had a relatively lower DI value than PI 567543C (unpublished data).…”

“…Aphid resistance was visually rated for each plant 3 weeks after infestation in the summer 2009 test and 3 and 4 weeks after infestation in the fall 2010 test, using a scale of 0-4 developed by Mensah et al (2005Mensah et al ( , 2008. The following criteria were used: 0 = no aphids; 0.5 = less than 10 aphids per plant, no colony formed; 1 = 11-100 aphids per plant, plant appears healthy; 1.5 = 101-150 aphids per plant, plant appears healthy; 2 = 151-300 aphids per plant, mostly on the young leaves or tender stems, plant appears healthy; 2.5 = 301-500 aphids per plant, plant appears healthy; 3 = 501-800 aphids per plant, young leaves and tender stems covered with aphids, leaves slightly curly and shiny; 3.5 = More than 800 aphids per plant, plants stunted, leaves curled and slightly yellow, no sooty mold and few cast skins; 4 = more than 800 aphids per plant, plant stunted, leaves severely curled and yellow, covered with sooty mold and cast skins.…”

“…A damage index (DI) for each line was calculated by the following formula (Mensah et al 2005): DI = P (Scale value 9 No. of plants in the category)/(4 9 Total no.…”

“…Therefore, finding new sources of resistance and new resistance genes is necessary to control the newly discovered or evolved biotypes. PI 567598B and its derived lines have strong antibiosis resistance (Mensah et al 2005) and resistance to soybean aphids as shown by biotype studies conducted in several states (Cooper 2012;Mian et al 2008a). However, little is known about the genomic locations of the two recessive genes for the aphid resistance in PI 567598B; this could hinder its utilization.…”

“…Antixenosis affects insect behavior and is expressed as non-preference for certain plants. Researchers in the US have identified several aphidresistant germplasm accessions (Hill et al 2004;Mensah et al 2005;Diaz-Montano et al 2006;Hesler et al 2007;Hesler and Dashiell 2008;Mian et al 2008a). Genetic studies have shown that the antibiosis resistance in Dowling and Jackson were both controlled by a single dominant gene (Hill et al 2006a, b).…”