Marker-Assisted Gene Pyramiding for Powdery Mildew Resistance in Thai Mungbean Variety SUT1 by Backcross Breeding

Abstract

In Thailand, all Thai cultivated varieties of mungbean [Vigna radiata (L.) R. Wilczek] preferentially grown by farmers are susceptible to powdery mildew (PM) disease. Marker-assisted gene pyramiding (MAGP) for improving resistant varieties is sustainable strategy to overcome its outbreak in mungbean elds. In this study, two PM resistance genes from donor parent A2 were pyramided into Thai cultivated variety, namely Suranaree University of Technology 1 (SUT1) using markerassisted backcrossing (MAB). Three polymorphic marker loci linked to PM resistance genes and three marker sets with 72 polymorphic loci were subsequently used for foreground and background selection, respectively. As a consequence, three pyramided BC 4 lines B1, B2, and D5 carrying all foreground marker loci in homozygosity were obtained. Their recurrent parent genome (RPG) recovery was 100.0%, 100.0%, and 98.8% for background marker Sets A, B, and C, respectively. In eld conditions, it was found that a low level of PM severity was exhibited in the pyramided BC line D5, which also had most of the agronomic traits similar or superior to SUT1. Moreover, the yield performance of this line was higher than SUT1, up to 8.3%-12.2% with no disease or PM outbreak. Thus, this pyramided BC line can be further used to develop a new resistant variety for farmers in the future. Key MessageNew mungbean breeding line D5 with two powdery mildew resistance genes was developed by marker-assisted gene pyramiding (MAGP). This backcross line which had better yield performance than recurrent parent SUT1 will be useful for improving resistant variety for prone areas with disease outbreaks and organic farming systems in the future.