Pathological and molecular characterizations of slow leaf rusting in fifteen wheat (<i>Triticum aestivum</i> L. em Thell) genotypes

Abstract

Leaf rust caused by Puccinia triticina, is a globally important fungal disease of wheat (Triticum aestivum L. em. Thell), resulting in significant yield losses, sometimes up to 40% worldwide. In this study we investigated slow rusting resistance at pathological and molecular level. Fifteen (15) wheat genotypes which also included multiple crosses with the aim to characterize pyramid resistance genes, including slow rusting genes like Lr46 and Lr50 were evaluated for disease severity percent, latent period and incubation period under field conditions. Detached leaf assay was also performed with three virulent pathotypes viz., 21R55 (104-2), 121R63-1 (77-5) and 29R45 (12-5), under controlled laboratory conditions. Genotypes, KIRITATAI//HUW234+LR34/PRINIA, WAXWING*2/TUKURU, WBLLI*2/KIRITATI, KAMBI*2/-BRAMBLING and KAMBI*2/KIRITATI were very close to near immunity and showed comparatively higher level of resistance against all the three pathotypes. Disease severity in resistant genotypes was traced type 5 to 6% in both years, while it was 60 to 80% in the case of susceptible genotypes, that is, ‘Agra Local’ (S1). Similar pattern was observed for AUDPC, that is, <250.0 in the resistant genotypes, while it was beyond 1000.0 in ‘Agra Local’. The shorter mean latent (7.67) and incubation period (6.0) was observed in susceptible genotypes, that is, ‘Agra Local’ to all the resistant genotypes, that is, LP (10 to 12) and IP (9 to 10); while testing against all the three different pathotypes. Linked microsatellite markers were used to confirm the presence of different rust resistance genes required to achieve near immunity. Out of 10 primers, nine produced gene specific bands with all genotypes except the control, that is, Agra Local. Genotypes which showed slow rusting, had longer latent period and incubation period as well as reduced percent disease severity and confirmed the presence of four to five resistance genes including slow rusting genes, that is, Lr46 and Lr50. This indicates that these genotypes have potential durable resistance and can be used as parental lines in the development of more durable rust resistance.

Key words: Near immunity, pathotypes, Puccinia triticina, SSR.