Breeding potential of lablab [Lablab purpureus (L.) Sweet]: a review on characterization and bruchid studies towards improved production and utilization in Africa

Lablab (Lablab purpureus L.) genotypes and field margin vegetation influence bean aphids and their natural enemies

Lablab (Lablab purpureus L.) is an important food and livestock feed legume that can also enhance soil fertility. However, its production is limited by insect pests, notably the black bean aphid (Aphis fabae). The present field study was conducted to determine the difference in the contribution of lablab genotypes and natural field margin vegetation (FMV) to the abundance and diversity of natural enemies and the damage, incidence, and abundance of bean aphids. Eighteen lablab genotypes were planted in the presence or absence of FMV in a randomized complete block design experiment replicated four times. Data on aphid abundance, incidence, and severity of damage were collected at four growth stages of the crop. Lablab genotypes significantly influenced aphid incidence, suggesting some level of tolerance to aphid colonization. Findings showed that lablab genotypes were a significant influence on natural enemy species richness with no statistical difference for abundance and natural enemy species diversity. However, the genotypes did not vary significantly in their influence on the number of aphid natural enemies. FMV was associated with low bean aphid damage. Overall, the presence or absence of FMV did not influence the number of natural enemies caught on the crop. This concurs with recent work that shows a similar number of natural enemies with field margin plants but may reflect the reduced number of pest insects. Cropping seasons influenced aphid abundance and damage severity, with the populations developing at the early stages of lablab development and decreasing as the crop advanced. This pattern was similar both in the presence or absence of FMV. The findings of this study highlight the important contribution of crop genotype together with the presence of field margin species in the regulation of aphids and their natural enemies in lablab.

Epicuticular wax chemicals of Lablab purpureus subsp. bengalensis influence short-range attraction and oviposition responses in Aphis craccivora and Aphis gossypii

Lablab purpureus subsp. bengalensis (Jacq.) Verdc. is an important legume of India and Africa. Both aphids, Aphis craccivora Koch and A. gossypii Glover (Hemiptera: Aphididae), are important herbivorous pests of this legume crop. These viviparous females lay nymphs on the leaf surface of this legume plant. Therefore, it is of considerable interest to study whether leaf surface wax chemicals (long-chain alkanes and free fatty acids) of this legume plant served as short-range attractants and oviposition stimulants in both females to lay nymphs. Twenty-one n-alkanes from n-C12 to n-C35 and 11 free fatty acids from C12:0 to C22:0 were identified in leaf surface waxes. Nonacosane and nonadecanoic acid were the most abundant among n-alkanes and free fatty acids, respectively. Both females were attracted towards one leaf equivalent surface wax against the control solvent (petroleum ether) in short Y-tube olfactometer bioassays. A synthetic blend of tetradecane, pentadecane, tetracosane, tridecanoic acid, tetradecanoic acid, and heneicosanoic acid comparable to one leaf equivalent surface wax served as short-range attractants and oviposition stimulants in A. craccivora; whereas a synthetic blend of tetradecane, hexadecane, docosane, nonadecanoic acid, and arachidic acid comparable to one leaf equivalent surface wax acted as short-range attractants and oviposition stimulants in A. gossypii. These results can provide the basis for efficient pest management strategies of A. craccivora and A. gossypii against L. purpureus subsp. bengalensis using host plant leaf surface wax compounds. Further, SEM studies of antennae and forelegs of both aphids were conducted to observe sensilla structures, which help in chemoreception.

Effects of genotype and environment on forage yield, nutritive value and morphology of lablab (Lablab purpureus (L.) sweet)

The goal of the study is to determine the effect of genotype and environment on forage yield, forage nutritive value and to determine the relation between morphology and forage yield and nutritive value of lablab. Thirteen genotypes (one local and 12 improved) were replicated 3 times in a randomized complete block trial across three locations in Ethiopian lowlands namely, Bechi, Kite and Tepi. All forage samples were analyzed for dry matter (DM), crude protein (CP), and in vitro dry matter digestibility (IVDMD) using a combination of conventional nutritional analyses and near infrared reflectance spectroscopy. There was a significant (P < 0.001) effect of genotype, location and genotype*location on forage yield of DM, forage yield of CP, forage yield of IVDMD, CP, and IVDMD. The difference between means of minimum and maximum genotypes was 12.9 t/ha of DM, 3.12 t/ha CP, 8.22 t/ha IVDMD, 57 g/kg of CP and 56 g/kg of IVDMD. The correlation between plant morphology and forage yield and nutritive value was weak (r ≤ 0.41) in all locations and the combined data. Both genotype and location should be considered by the farmers when they decide to grow lablab for forage production. Morphological traits of lablab are not suitable to evaluate forage yield and nutritive value. Enhancing the awareness of farmers about the effect genetic-environment interaction effect of forage yield and nutritive value and the relation between morphology and yield and nutritive value would improve the uptake of lablab in mixed the farming system leading to more sustainable agricultural production.

Combating ozone stress through N fertilization: A case study of Indian bean (Dolichos lablab L.)

The present study investigates the efficiency of nitrogen (N) amendments in the management of ozone (O₃) stress in two varieties (Kashi Sheetal and Kashi Harittima) of Indian bean (Dolichos lablab L.). Two O₃ concentrations, ambient (44.9 ppb) and elevated (74.64 ppb) were used, and each O₃ concentration has 3 nitrogen (N) dose treatments viz recommended (N1), 1.5 times recommended (N2), 2 times recommended (N3) and no nitrogen, which served as control (C). The experiment concluded Kashi Sheetal as O₃ tolerant, as compared to Kashi Harittima. N amendments were effective in the partial amelioration of O₃ stress, with N2 being the most effective nitrogen dose, at both ambient and elevated O₃ concentrations. Kashi Sheetal has been determined to be O₃ tolerant due to greater endogenous levels of H₂O₂ accumulation and enzymatic antioxidant contents with O₃ exposure. The O₃-sensitive variety, Kashi Harittima, responded more positively to N treatments, at both O₃ concentrations. The positive effect of N amendments is attributed to the stimulated antioxidative enzyme activity, rather than the biophysical processes like stomatal conductance. Strengthened defense upon N amendments was attributed to the enhanced activities of APX and GR in Kashi Sheetal, while in Kashi Harittima, the two enzymes (APX and GR) were coupled by SOD and CAT as well, during the reproductive phase. Yield (weight of seeds plant^-1) increments upon N (N2) amendments were higher in Kashi Harittima (O₃ sensitive), as compared to Kashi Sheetal (O₃ tolerant) at both ambient and elevated O₃ concentration, due to higher antioxidant enzymatic response and greater rate of photosynthesis in the former.

Debulking different Corona (SARS-CoV-2 delta, omicron, OC43) and Influenza (H1N1, H3N2) virus strains by plant viral trap proteins in chewing gums to decrease infection and transmission

Because oral transmission of SARS-CoV-2 is 3-5 orders of magnitude higher than nasal transmission, we investigated debulking of oral viruses using viral trap proteins (CTB-ACE2, FRIL) expressed in plant cells, delivered through the chewing gum. In omicron nasopharyngeal (NP) samples, the microbubble count (based on N-antigen) was significantly reduced by 20 μg of FRIL (p < 0.0001) and 0.925 μg of CTB-ACE2 (p = 0.0001). Among 20 delta or omicron NP samples, 17 had virus load reduced below the detection level of spike protein in the RAPID assay, after incubation with the CTB-ACE2 gum powder. A dose-dependent 50% plaque reduction with 50-100 ng FRIL or 600-800 μg FRIL gum against Influenza strains H1N1, H3N2, and Coronavirus HCoV-OC43 was observed with both purified FRIL, lablab bean powder or gum. In electron micrographs, large/densely packed clumps of overlapping influenza particles and FRIL protein were observed. Chewing simulator studies revealed that CTB-ACE2 release was time/dose-dependent and release was linear up to 20 min chewing. Phase I/II placebo-controlled, double-blinded clinical trial (IND 154897) is in progress to evaluate viral load in saliva before or after chewing CTB-ACE2/placebo gum. Collectively, this study advances the concept of chewing gum to deliver proteins to debulk oral viruses and decrease infection/transmission.

Farmers' Participatory Plant Selection of Lablab (Lablab purpureus (L.) Sweet) in Tanzania

Farmer-participatory breeding approach is an important component in the crop improvement of lablab (Lablab purpureus (L.) Sweet). The study was carried out to obtain the knowledge, practices and preferences of lablab through 31 lablab growing-farmers from Arusha, Kondoa, Karatu, Same and Babati districts of Tanzania toward initiating a lablab breeding program. Semi-structured questionnaires were administered and focused group discussions were held to collect data on the socio-demographic factors, production practices, constraints and farmer's preferred traits of lablab. Selection of preferred traits and accessions was also done by the farmers in the field. Results showed that the chief constraints of lablab production are pests and diseases, poor marketability, low seed quality, inadequate rainfall, expensive agrochemicals, low yield, and poor storage facilities. The major pests are pod borer (field) and bruchids (storage). Preferred traits for lablab improvement include the development of insect pests and disease-resistant varieties, early maturing, high yield, black colored seed for market, short cooking time, and dense foliage. Genotypes EK2, D360, HA4, and D96 with preferred traits were identified by farmers, which forms critical decisions in crop improvement. This study describes the current view of lablab production and generates the understanding of farmers' perceptions and preferences vital for breeding priorities and programs to increase its production, utilization and consumption.