Characterization of bean common mosaic virus isolates infecting three leguminous bean crops from South and Southeast Asia.

Bean common mosaic virus (BCMV) is causing economically important diseases in leguminous crops worldwide. In this study, BCMV isolates from country bean (CB, Lablab purpureus), yard-long bean (YLB, Vigna unguiculata) and rajma bean (RB, Phaseolus vulgaris) collected from Bangladesh, Nepal and Cambodia were characterized. Samples tested positive for BCMV in serological assays were subjected to high-throughput sequencing to generate near full-length genome sequences. In pair-wise comparisons of the polyprotein open reading frame, thirteen BCMV isolates from Bangladesh, Cambodia, and Nepal showed sequence identity of 92.1 to 98.8% at the nucleotide and 94.2 to 99% at the amino acid level among themselves and with corresponding sequences of BCMV reported previously. In phylogenetic analyses using the global BCMV sequences, they segregated into five distinct lineages, with RB isolates from Nepal clustering with US1/NL1-clade of common bean isolates from different countries, YLB isolates aligning with blackeye cowpea strain sequences reported from China, and CB isolates from Nepal and Bangladesh clustering with soybean isolates from China. One YLB isolate from Nepal was identified as a putative recombinant. None of the BCMV sequences aligned with isolates representing the RU1 or PStV clades. In grow-out tests, seed samples from local markets showed 14.3 to 38.1% transmission efficiency rate of BCMV with CB seed lots and from 9.5% to 33.3% with YLB seed lots.

Extraction and characterization of starch from Yard-long bean (Vigna unguiculata (L.) Walp. ssp. unguiculata cv.-gr. sesquipedalis).

Vigna unguiculata subsp. sesquipedalis is an important derivative cultivar of cowpea planted widely in China, and popularly known as "Yard-long bean". There is lack of research about the structural characterization and physicochemical aspects of carbohydrate content in Yard-long bean seeds. Thus, the present study aimed to evaluate structures, thermal and technological properties of Yard-long bean seeds starch (YSS). The starch contains little of ash, protein and total fiber meanwhile amylose content of 37.52%. The shapes of the starch granules obtained from field emission scanning electron microscopy (FESEM) were oval to semi-elliptical with little granules occurring in agglomerated structures clusters, and volume median diameter of granules ranged from 10.5 µm to 12.5 µm. The initial gelatinization temperature of YSS was 73.86 °C, peak temperature was 80.59 °C and final 88.53 °C. Solubility index (SI, 3.43% at 90 °C) and swelling power (SP, 6.62 g/g at 90 °C) were observed with low volume, which corroborated with the C-type structure shown by X-ray diffraction (XRD) and high crystallinity degree. The extraction of YSS can be feasible, and it has suitable properties for use in the food industry.

Same Locus for Non-shattering Seed Pod in Two Independently Domesticated Legumes, Vigna angularis and Vigna unguiculata.

Loss of pod shattering is one of the most important domestication-related traits in legume crops. The non-shattering phenotypes have been achieved either by disturbed formation of abscission layer between the valves, or by loss of helical tension in sclerenchyma of endocarp, that split open the pods to disperse the seeds. During domestication, azuki bean (Vigna angularis) and yard-long bean (Vigna unguiculata cv-gr. Sesquipedalis) have reduced or lost the sclerenchyma and thus the shattering behavior of seed pods. Here we performed fine-mapping with backcrossed populations and narrowed the candidate genomic region down to 4 kbp in azuki bean and 13 kbp in yard-long bean. Among the genes located in these regions, we found MYB26 genes encoded truncated proteins in azuki bean, yard-long bean, and even cowpea. As such, our findings indicate that independent domestication on the two legumes has selected the same locus for the same traits. We also argue that MYB26 could be a target gene for improving shattering phenotype in other legumes, such as soybean.

A study on Maruca vitrata infestation of Yard-long beans (Vigna unguiculata subspecies sesquipedalis).

Globally, Maruca vitrata (Geyer) is a serious yield constraint on food legumes including Yard-long bean (Vigna unguiculata subspecies sesquipedalis). However, there is a dearth of information on its damage potential, distribution and population dynamics in Yard-long beans. In the present study, the level of M. vitrata larval infestation on flowers and pods of Yard-long beans in Sri Lanka was determined with respect to three consecutive cropping seasons, Yala, Off and Maha. Results indicated that larval infestation and abundance varied with developmental stage of flowers and pods, cropping season and their combined interactive effects. Flowers of Yard-long beans were more prone to M. vitrata larval attack compared to pods. Abundance and level of infestation of M. vitrata varied with plant parts, having a ranking of flower buds (highest) > open flowers > mature pods > immature pods (lowest). Peak infestation was observed six and eight weeks after planting on flowers and pods, respectively. Among the three cropping seasons, M. vitrata infestation was found to be higher during Maha and Off seasons compared to Yala. The findings of this study contribute to the identified knowledge gap regarding the field biology of an acknowledged important pest, M. vitrata, in a previously understudied crop in Sri Lanka.