New Sources of Resistance in Sorghum (Sorghum bicolor) Germplasm Are Effective Against a Diverse Array of Potyvirus spp.

Abstract

Seifers, D. L., Perumal, R., and Little, C. R. 2012. New sources of resistance in sorghum (Sorghum bicolor) germplasm are effective against a diverse array of Potyvirus spp. Plant Dis. 96:1775Dis. 96: -1779 Sorghum is a host to numerous Potyvirus spp. and its germplasm encompasses a wide range of infection responses to these viruses. We determined how 183 mini-core-collection sorghum germplasm accessions responded to mechanical inoculation with Maize dwarf mosaic virus (MDMV) in growth regimes in which they were maintained at 30°C followed by 16°C for 5 days. Accessions that appeared immune to MDMV in this initial screening were evaluated for their response in a similar temperature maintenance regime to mechanical inoculation with MDMV, Sugarcane mosaic virus strain MDB (SCMV-MDB), Sorghum mosaic virus (SrMV), Zea mosaic virus (ZeMV), and Kansas, Nigerian, and Australian isolates of Johnsongrass mosaic virus (JGMV-KS, -N, and -Aus, respectively). In both experiments, MDMV systemically infected all accessions except international sorghum accession number (IS) 7679 and IS 20740. These accessions also proved resistant to MDMV, SCMV-MDB, SrMV, and JGMV-N but both were susceptible to the JGMV-KS and JGMV-Aus isolates. IS 7679 but not IS 20740 was resistant to infection with ZeMV. These observations suggest that IS 7679 and IS 20740 might serve as new sources of resistance to several Potyvirus spp. that systemically infect sorghum. (ZeMV). Of these, MDMV and SCMV-MDB are most often associated with the disease called maize dwarf mosaic of corn and sorghum (21,22). JGMV has also been documented to naturally infect sorghum in the United States (14,17). A few instances of natural infection of sorghum with SrMV in Texas have been reported (9), and ZeMV occurs in Israel, where it infects maize and sorghum (18). Sorghum (Sorghum bicolor (L.) Moench) is a host to several virus species of the family Potyviridae, including Maize dwarf mosaic virus (MDMV) (formerly MDMV-A), Sugarcane mosaic virus strain MDB (SCMV-MDV; formerly MDMV-B), Johnsongrass mosaic virus (JGMV), Sorghum mosaic virus (SrMV), and Zea mosaic virusMaize dwarf mosaic of sorghum has been recognized as an important disease of sorghum in the United States (22). Two principal vectors of MDMV and SCMV-MDB are the corn leaf aphid, Rhopalosiphum maidis (Fitch), and the greenbug, Schizaphis graminum Rond. (4,7). At warm temperatures, sorghum plants respond initially to infection with mosaic symptoms but produce a red-leaf symptom when they are exposed to cooler temperatures of about 16°C (12,21). This symptom is a consequence of the necrosis induced by infection. The term "red-leaf" is also applied to sorghum genotypes that produce tan pigments during necrosis (10). In earlier literature, the mosaic reaction was described as a "resistant" response (8), although it demonstrated susceptibility to systemic virus infection. Other authors have described this "mosaic-only" response to infection at different temperatures as resistance, "tolerance", or as a reaction f...

Genetic Variability and Effect of Postflowering Drought on Stalk Sugar Content in Sorghum Mini Core Collection

“…K.J. Leonard & Suggs] (Sharma et al, 2012), while IS 13294 and 13549 were reported resistant to maize dwarf mosaic virus (Seifers et al, 2012). In terms of susceptibility to insect pests, research at ICRISAT has shown that while most of these accessions were reported highly susceptible to stem borer ( Chilo partellus S.), IS 1004, 4698, and 23216 were resistant to stem borer.…”

Multi-Trait Diverse Germplasm Sources from Mini Core Collection for Sorghum Improvement

“…On the basis of sorghum mini core accessions grown in two post-rainy seasons under optimally irrigated and drought-stressed conditions, the sources for earliness (flowered <60 DAS), greater seed size, and high grain yielding accessions were identified. Further, published information on the response of sorghum mini core accessions [11] to biotic [12][13][14][15][16][17] and abiotic [17][18][19] stresses, and for grain nutritional [20] and bioenergy traits [21,22] (Table 1) were used to identify genetically diverse trait-specific sources for use in sorghum breeding globally.…”

“…Sorghum mini core accessions have been extensively evaluated for resistance to diseases [12][13][14][15][16][17], and insect pests (ICRISAT Unpublished), and the identified sources of resistance are listed in Table 1. These includes 53 accessions with resistance to downy mildew (three accessions, IS 28747, IS 28449 and IS 30400, for Patancheru isolate of Peronosclerospora sorghi and 47 accessions for pathotype 6 (P6), a new virulent pathotype of P. sorghi in Texas and three accessions, IS 23992, IS 27697 and IS 31714, resistant to both Patancheru isolate and P6), 50 for grain mold, 27 for leaf blight, 13 for anthracnose, six for rust, 32 for sugarcane aphid (Melanaphis sacchari), six for spotted stem borer (Chilo partellus) and four for shoot fly (Atherigona soccata).…”

“…In this study, the evaluation of sorghum mini core collection under optimally irrigated and drought-stressed conditions during two post-rainy seasons resulted in the identification of 21 germplasm as sources for important agronomic traits namely early flowering, greater seed weight and high grain yield, for their utilization in crop improvement. The sorghum mini core collection has been extensively evaluated by researchers globally and sources for various traits identified for use in sorghum breeding programs [12][13][14][15][16][17][18][19][20][21][22]. The agronomic performance of these trait-specific accessions is a key factor to utilize them in breeding programs.…”

“…Greater use of such diversity in sorghum breeding programs so as to develop cultivars with a broad genetic base will result in sustainable sorghum production. The aim of the present investigation was to assess the agronomic performance of sorghum mini core collection [11], a germplasm diversity panel representative of the global sorghum collection, and identify genetically diverse multi-trait-specific germplasm sources, considering agronomic performance and published information on the response of sorghum mini core accessions to biotic [12][13][14][15][16][17] and abiotic [17][18][19] stresses, and for grain nutritional [20] and bioenergy traits [21,22].…”