Distinctive Physio-Biochemical Properties and Transcriptional Changes Unfold the Mungbean Cultivars Differing by Their Response to Drought Stress at Flowering Stage

Mungbean is a nutritionally and economically important pulse crop cultivated around Asia, mainly in India. The crop is sensitive to drought at various developmental stages of its growing period. However, there is limited or almost no research on a comparative evaluation of mung-bean plants at the flowering stage under drought conditions. Hence, the aim of this research was to impose the drought stress on two mungbean cultivars VRM (Gg) 1 and CO6 at the flowering stage and assess the physio-biochemical and transcriptional changes. After imposing the drought stress, we found that VRM (Gg) 1 exhibited a low reduction in physiological traits (Chlorophyll, relative water content, and plant dry mass) and high proline content than CO6. Additionally, VRM (Gg) 1 has a low level of H2O2 and MDA contents and higher antioxidant enzymes (SOD, POD, and CAT) activity than CO6 during drought stress. The transcriptional analysis of photosynthesis (PS II-PsbP, PS II-LHC, PS I-PsaG/PsaK, and PEPC 3), antioxidant (SOD 2, POD, CAT 2), and drought-responsive genes (HSP-90, DREB2C, NAC 3 and AREB 2) show that VRM (Gg) 1 had increased transcripts more than CO6 under drought stress. Taken together, VRM (Gg) 1 had a better photosynthetic performance which resulted in fewer reductions in chlorophyll, relative water content, and plant dry mass during drought stress. In addition, higher antioxidative enzyme activities led to lower H2O2 and MDA levels, limiting oxidative damage in VRM (Gg) 1. This was positively correlated with increased transcripts of photosynthesis and antioxidant-related genes in VRM (Gg) 1. Further, the increased transcripts of drought-responsive genes indicate that VRM (Gg) 1 has a better genetic basis against drought stress than CO6. These findings help to understand the mungbean response to drought stress and will aid in the development of genotypes with greater drought tolerance by utilizing natural genetic variants

The Hunt for Mungbean (<i>Vigna radiata</i> (L.) Wilczek) Genotypes and Breeding Lines Resistance to South Indian Bruchid Strain

Mungbean (Vigna radiata) is an important short-season legume widely cultivated in Asia, particularly India. It is highly susceptible to bruchids and developing bruchid resistance is an important goal in mungbean breeding programs. In the present study, 52 mungbean genotypes were evaluated for bruchid resistance based on the “no-choice test” and identified two highly resistant genotypes (V2802BG and V2709) with no adult emergence and seed damage. Further, these two resistant genotypes were crossed with six high-yielding bruchid susceptible cultivars (CO 5, CO 6, CO 7, CO 8, VBN 2, and VBN 3), and 12 independent F1 populations were generated. Of these, one population derived from CO 6 × V2802BG was selected (based on the good combining ability of the parents) and forwarded to later generations to trace the bruchid-resistant lines. A total of 159 F2:3 families were screened for bruchid resistance, and the results showed that seven families were highly resistant, whereas the remainder were resistant to highly susceptible. Further, those seven families were evaluated in F4 and F5 generations. As a result, five highly resistant lines (BSR-GG-1-49-3-1, BSR-GG-1-56-2-2, BSR-GG-1-160-5-3, BSR-GG-1-170-2-4, and BSR-GG-1-198-1-4) with good agronomic performances were identified. The newly developed lines could be tested in multi-location trials and then be utilized as a potential source of genetic material for improving the bruchid resistance in mungbean breeding programs