Yellow mosaic disease (YMD), incited by mungbean yellow mosaic virus (MYMV), is a primary viral disease that reduces mungbean production in South Asia, especially in India. There is no detailed knowledge regarding the genes and molecular mechanisms conferring resistance of mungbean to MYMV. Therefore, disclosing the genetic and molecular bases related to MYMV resistance helps to develop the mungbean genotypes with MYMV resistance. In this study, transcriptomes of mungbean genotypes, VGGRU-1 (resistant) and VRM (Gg) 1 (susceptible) infected with MYMV were compared to those of uninfected controls. The number of differentially expressed genes (DEGs) in the resistant and susceptible genotypes was 896 and 506, respectively. Among them, 275 DEGs were common between the resistant and susceptible genotypes. Functional annotation of DEGs revealed that the DEGs belonged to the following categories defense and pathogenesis, receptor-like kinases; serine/threonine protein kinases, hormone signaling, transcription factors, and chaperons, and secondary metabolites. Further, we have confirmed the expression pattern of several DEGs by quantitative real-time PCR (qRT-PCR) analysis. Collectively, the information obtained in this study unveils the new insights into characterizing the MYMV resistance and paved the way for breeding MYMV resistant mungbean in the future.

Background: Mung bean Yellow Mosaic Virus (MYMV) is found to be one of the prime viral diseases of mungbean in Tamil Nadu state. Screening for MYMV resistance in field condition always remains a hassle for breeding society. The peculiar MYMV symptoms often failed in the field due to some factors such as environmental changes, whitefly genotypes, host factors etc. With the above perspective, the present study aimed to screen the mung bean derivatives against MYMV through a novel in vitro agroinoculation technique and further substantiation through whitefly transmission. Methods: Four interspecific derivatives (VGGRU 1, VGGRU 2, VGGRU 3 and VGGRU 4) generated by making crosses between mungbean VRM (Gg) 1 and rice bean (TNAU RED) along with the susceptible check VRM (Gg) 1 were agroinoculated with the MYMV infectious clone VA 239 (KA30 DNA A + KA27 DNA) and are further substantiated through whitefly transmission studies from the artificially reared whiteflies. Result: The agroinoculation results revealed that among the four interspecific derivatives, VGGRU 1 was found to be completely resistant to MYMV. The substantiation of the obtained result through whitefly transmission also revealed that 24 h Acquisition Access Period (AAP) and 24 h Inoculation Access Period (IAP) with Bemisia tabaci able to cause 65% infectivity in susceptible plant VRM (Gg) 1 and zero infectivity in VGGRU 1 and the results were PCR confirmed for the presence of viral DNA.

Yellow Mosaic Disease (YMD) caused by mungbean yellow mosaic virus (MYMV, begomovirus) is one of the main causes of low mungbean (Vigna radiata L.) productivity, primarily in South Asia. Agroinoculation screening for MYMV resistance in mungbean cultivar VGGRU 1, an interspecific derivative of mungbean × rice bean and VRM (Gg)1 across replications, revealed VGGRU1 as highly resistant to MYMV infection. Gas chromatography mass spectrometry analysis was performed on the methanolic leaf extracts of susceptible and resistant genotypes, along with necessary controls. The metabolite profiling of the susceptible and resistant genotypes, along with controls, identified 121 discriminant metabolites belonging to 24 different classes of metabolites. A maximum number of 27 metabolites were accumulated in agroinoculated VGGRU1 alone. Metabolite profiles of VGGRU1 and VRM1 were clustered hierarchically and revealed substantial variations between the genotypes. Fold change revealed the upregulation of amino acids and phenol in the resistant genotype. The resistant genotype, VGGRU1, showed significantly higher levels of key defense-related metabolites, such as amino acids and phenolics. In this study, 18 significant VIP metabolites were identified, differentiating the resistant VGGRU1 and susceptible VRM (Gg)1 genotypes.