Characterization of Soybean Mosaic Potyvirus and Screening of Soybean Germplasm for the Source of Resistance to IT

Abstract

Soybean Mosaic potyvirus (SMV) occurred widely in major soybean growing areas of the NWFP. Infected plants exhibited predominantly mosaic and mottling symptoms on leaves and stunted the growth due to shortened petioles and internodes. Incidence of the virus ranged from mild to severe infection between 8-72% (average of 40%) in areas surveyed. ELISA test further confirmed incidence of the virus from 7 to 64% (average of 35.5%) during 1997-1998 and 10-47% (average of 30.6%) during 1999-2000 in major soybean growing areas of NWFP. Twelve soybean isolates were collected from soybean crop growth in different areas, which caused characteristics and distinguishable mosaic and mottling symptoms. Out of these, six isolates three each from Swat (SMV-S1, S2, S3) and Peshawar area (SMV-P1, P2, P3) were selected for further biological characterization. SMV-S1, S2, S3 produced severe mosaic on mechanically inoculated soybean (Glycine max) cv. Weber-84, leaf chlorosis and chlorotic local lesions on Phaseolus valgaris and P. lunatus, and local lesions on Chenopodium amaranticolor and C. quinoa. SMV-P1, P2, and P3 isolates caused mild mosaic on soyabean cv. Weber-84, while identical reaction was recorded in P.vulgaris and Chenopodium species. On the basis of biological characterization SMV isolates S1 and P1 were selected for further studies. None of the 29 soybean cultivars and 40 breeding lines screened for resistance, was found immune to two isolates of soybean mosaic potyvirus (SMV-S1 and SMV-P1). Malakand-96 was the only cultivars found highly resistant to both S1 and P1 isolates. Swat-84, Bryan, Hobbit-87, Kingsy, Lugan, Sherman and Harper-87 were resistant to S1 and P1 whereas Rincondita was resistant to S1 and moderately resistant to P1 isolate. Similarly, Clark, Nare, NARC-V and Wahab-93 were resistant to P1 but not to S1 isolate. Wahab-93, Kharif-93, Ajmeri, Hodgdon, Mid-spray, Full-Walter, NARC-II, NARC-IV, NARC-VI, Clark and Nare were moderately resistant to S1 whereas Kharif-93, Ajmeri, Hodgson, Full-water, NARC-II, NARC-IV, Rincondita, Mid-pharoah, NARC-VI and Winchester were moderately resistant to P1 isolate. William, Rawal-1, Mid-pharoah, Bass, NARC-III, NARC-I, NARC-V and Winchester were susceptible to SMV-S1 whereas William, Rawa-I, Mid-Spray, Bass, NARC-I and NARC-III were susceptible to P1. Weber -84 was highly susceptible to both isolates of SMV. Among 40 soybean lines, GC-81083-63, GC-81084-51, GC-80072-2-6, AGS-253 and AVRDC-12, AVRDC-13 and AVRDC-15 were highly resistant to both isolates of SMV. Lines GC-81075-44, GC-81090-108, GC-81084-147, GC-81090-10, AGS-294, AGS-85, AVRDC-10, AGS-297, AVRDC-7 were resistant to both S1 and P1 isolates whereas L-85-2308, AVRDC-14, AVRDC-5, were resistant to S1 and moderately resistant to P1 isolate. Similarly, GC-81080-13, GC-82117-8, AGS-154, L-88-8502, AVRDC-3, AVRDC-4, AVRDC-8 were moderately resistant to S1 and P1 isolates and AVRDC-11, GC-81084-134, GC-81084-41, GC-81080-36, GC-81090-94, AVRDC-2, AVRDC-6 were moderately resistant to only P1 isolate. Ten soybean lines were susceptible and 3 highly susceptible to S1 whereas 4 lines were susceptible and only one was highly susceptible to P1 isolate. Soybean germplasm found highly resistant or resistant to two prevalent SMV isolates in screen house experiment were exposed to field conditions. Among 13 soybean cultivars, Malakand-96, Bryan and Sherman developed no symptoms and no virus was detected by ELISA. Wahab-93, Lugan, Hobbit, Kingsay, Harper, Nare, NARC-V and Clark developed a mild mosaic and light veinal chlorosis on a few young leaves. Among soybean lines, GC-81083-63, GC-81084-51, GC-80072-2-6, AGS-253 and AVRDC-13, no visible host reaction was observed. AVRD-12 and AVRDC-15 responded mild mosaic on a few leaves. The soybean cultivars such as Malakand-96, Bryan, and Sherman and lines such as GC-81083-63, GC-81084-51, GC-80072-2-6, AGS-253 and AVRDC-13 were further tested in screen house experiments by inoculating isolates S1 through green peach aphids (Myzus persicae). Three soybean cultivars and four lines exhibited a mild mosaic on young leaves. A low virus concentration has been detected in resistant soybean germplasm.