Manish Srivastav

Bio-active compounds in mango (Mangifera indica L.) and their roles in human health and plant defence – a review

Summary Mango (Mangifera indica L.) is one of the most important tropical fruits in the World. Mango leaves, bark, and fruit (pulp, peel, and stone) are rich sources of bio-active compounds (BaCs) such as proteins [0.36 – 0.40 g 100 g–1 fresh weight (FW) of pulp; 1.76 – 2.05% (w/w) of peel; 66.1 g kg–1 of kernel flour; and 3.0% (w/w) of leaves], vitamin A [0.135 – 1.872 mg 100 g–1 FW pulp; 15.27 International Units (IU) in kernels; 1,490 IU in leaves], vitamin C [7.8 – 172.0 mg 100 g–1 FW of pulp; 188 – 349 µg g–1 FW of peel; 0.17 g kg–1 DW of kernel flour; 53 mg 100 g–1 dry matter (DM) in leaves], carotenoids (0.78 – 29.34 µg g–1 FW of pulp; 493 – 3,945 µg g–1 FW of peel), mangiferin (1,690.4 mg kg–1 DM in peel; 4.2 mg kg–1 DW of kernel extract), phenolic compounds, dietary fibre (DF), carbohydrates, minerals, and other anti-oxidants known to have medicinal, nutritional, and industrial benefits. Bio-active compounds exist in functional foods and can protect us against diseases via several mechanisms. The anti-oxidant properties of several BaCs are important to protect against diseases related to oxidative stress. Fruit intake provides us with anti-oxidants that may act in a synergistic way to offer protection. In mango fruit, only the pulp is used, while all other parts are discarded and cause environmental pollution. The importance of all the different parts of mango fruit and trees should not be disregarded. With a global increase in health issues there is an increasing demand for natural foods. Hence, there is need to study all the bio-active constituents in mango to provide greater insights into their medical, nutritional, and industrial applications, as well as their role(s) in defending of the plant. This review aims to assist in the proper utilisation of mangoes to improve nutrition and health, as well as to improve our understanding of the defence mechanisms in plants that depend on these compounds.

Paclobutrazol minimises the effects of salt stress in mango (Mangifera indica L.)

Summary We investigated the effects of paclobutrazol (PBZ) on 1-year-old plants of ‘Olour’ mango subjected to NaCl stress under polythene tunnel conditions. Plants were treated with two levels of salt [0.0 g NaCl kg−1 soil (control) or 1 g NaCl kg−1 soil] and three concentrations of paclobutrazol [PBZ; 0.0 mg l−1 (control), 750 mg l−1 or 1,500 mg l−1] after 30 d of establishment. Mortality in saline-treated mango plants was reduced significantly (LSD = 8.55; P ≤ 0.05) following the application of PBZ. NaCl-stress reduced the survival of plants without PBZ treatment by 89%, but only by 28.4% for 1,500 mg l−1 PBZ-treated plants. PBZ-treated plants also showed less defoliation, and fewer leaves per plant exhibited salt stress symptoms. It was also evident that treatment with PBZ increased the relative water and chlorophyll contents of mango seedlings, and reduced membrane injury, under salt stress. Furthermore, saline treatment without PBZ increased the Na+ and Cl− ion contents of leaves and roots; however, application of PBZ consistently and significantly lowered these ion contents (P ≤ 0.05). The Na+ content of leaves on saline-treated plants was reduced by 1.96- to 2.12-fold, whereas Cl− ion contents were reduced by 22 – 39% by PBZ treatment compared to salt-treated seedlings without PBZ. Our results suggest a role for PBZ in promoting the avoidance of salt stress in mango by increasing the levels of photosynthetic pigments, water content, K+ uptake and accumulation, and by reducing defoliation, the membrane injury index, and the uptake and accumulation of harmful Na+ and Cl− ions. These findings may be used to improve the yields and quality of mango trees grown in salt-affected areas.

Leaf Transcriptome Sequencing for Identifying Genic-SSR Markers and SNP Heterozygosity in Crossbred Mango Variety ‘Amrapali’ (Mangifera indica L.)

Mango (Mangifera indica L.) is called “king of fruits” due to its sweetness, richness of taste, diversity, large production volume and a variety of end usage. Despite its huge economic importance genomic resources in mango are scarce and genetics of useful horticultural traits are poorly understood. Here we generated deep coverage leaf RNA sequence data for mango parental varieties ‘Neelam’, ‘Dashehari’ and their hybrid ‘Amrapali’ using next generation sequencing technologies. De-novo sequence assembly generated 27,528, 20,771 and 35,182 transcripts for the three genotypes, respectively. The transcripts were further assembled into a non-redundant set of 70,057 unigenes that were used for SSR and SNP identification and annotation. Total 5,465 SSR loci were identified in 4,912 unigenes with 288 type I SSR (n ≥ 20 bp). One hundred type I SSR markers were randomly selected of which 43 yielded PCR amplicons of expected size in the first round of validation and were designated as validated genic-SSR markers. Further, 22,306 SNPs were identified by aligning high quality sequence reads of the three mango varieties to the reference unigene set, revealing significantly enhanced SNP heterozygosity in the hybrid Amrapali. The present study on leaf RNA sequencing of mango varieties and their hybrid provides useful genomic resource for genetic improvement of mango.

EFFECT OF PACLOBUTRAZOL AND PUTRESCINE ON ANTIOXIDANT ENZYMES ACTIVITY AND NUTRIENTS CONTENT IN SALT TOLERANT CITRUS ROOTSTOCK SOUR ORANGE UNDER SODIUM CHLORIDE STRESS

The effects of paclobutrazol (PBZ) and putrescine (Put) on antioxidant enzymes activity, proline contents and nutrients uptake were studied on salt tolerant citrus rootstock sour orange. Six-month-old nucellar seedlings grown in pots and subjected to three levels of PBZ and two levels each of salinity and Put for 90 days. Seedlings treated with PBZ or Put alone or in combination had higher anti-oxidant enzymes activities, accumulation of proline and nutrients contents like potassium (K+) and calcium (Ca2+) under both saline and non-saline conditions. Further, application of PBZ or Put alone or in combination also reduced the accumulation of both Na+ and Cl− ions in leaves and roots in NaCl stressed seedlings. A combined application of 250 mg L−1 PBZ and 50 mg L−1 Put proved to be more effective in improving proline and Ca2+ content and restricting accumulation of Na+ ions in leaf tissues.

Effect of NaCl in the irrigation water on growth, anti-oxidant enzyme activities, and nutrient uptake in five citrus rootstocks

Summary Seven–month-old, uniform-sized seedlings of five citrus rootstocks [sour orange (Citrus aurantiam), Attani-2 (C. rugulosa), Troyer citrange (C. sinensis × Poncirus trifoliata), billikhichlli (C. reshni), and RLC-6 (C. jambhiri)] were irrigated to 70% of field capacity with water containing 0, 50, 100, or 200 mM NaCl for 180 d. Growth, in terms of plant heights and the numbers of leaves, decreased with increasing levels of salinity in all five rootstocks. The decrease in plant height was greatest in the salt-susceptible Troyer citrange and billikhichlli at higher levels of salinity. However, in the salt-tolerant sour orange and Attani-2, NaCl caused only a slight decrease in plant height. Defoliation was maximum in the salt-susceptible Troyer citrange and billikhichlli. The maximum increases in superoxide dismutase (SOD) and peroxidase (POD) activities were found in the salt-susceptible Troyer citrange at higher levels of salinity. Leaf proline contents increased most in Attani-2, sour orange, and RLC-6 at higher levels of salinity.The concentration of Na+ ions in leaf tissues increased to a maximum in Attani-2; while, in root tissues, RLC-6 and Troyer had the highest Na+ ion contents. The maximum increase in leaf Cl– ion levels occurred in Troyer citrange, and the minimum was in RLC-6, at 200 mM NaCl. These data suggest that higher levels of proline accumulation and leaf abscission could be used as indicators for screening citrus rootstocks for resistance to NaCl stress. Sour orange and Attani-2 were able to exclude Cl– ions, whereas Troyer citrange appeared to exclude Na+ ions at lower levels of NaCl. Further studies are required to observe the translocation of harmful and beneficial mineral elements to scion cultivars grafted onto sour orange and Attani-2 and grown under NaCl stress. Overall, salt-tolerance increased in the following order: Troyer ì billikhichlli ì RLC-6 ì Attani-2 ì sour orange.

Effect of hot water treatment on the incidence of lenticel browning and quality of mango fruits

The present investigation was undertaken to evaluate the effect of hot water treatment on the incidence of lenticel browning (LB) in mango, which is becoming one of the main problems in handling and trade of fresh fruits. Fruits of four selected mango varieties (Indian – ‘Dashehari’, ‘Langra’; Exotic – ‘Sensation’, ‘Eldon’) which were found susceptible to LB, were subjected to hot water treatment (HWT) at different levels (45°, 50° and 55°C for 30 min.). After treatment, the fruits were stored at ambient conditions (35 ± 4oC and 65 ± 5% RH) for 10 days. At the end of storage period, observations were recorded on various parameters. Our results revealed that fruits of ‘Langra’ exhibited 100% LB, followed by ‘Dashehari’ (52.8%), ‘Sensation’ (35.9%) and ‘Eldon’ (28.3%). All levels of hot water treatment reduced the LB to a greater extent as well as improved fruit quality attributes significantly over untreated fruits. The best results were obtained with HWT at 50°C for 30 min. for reducing LB and fruit decay in different mango varieties and maintaining better quality over untreated fruits. Thus, it can be concluded that hot water treatment at 50°C for 30 min. could be recommended for reducing incidence of LB in mango.

Effect of pre-harvest application of salicylic acid on postharvest behaviour of ‘Amrapali’ mango fruits during storage

Mango is a highly perishable and deteriorates at a very fast rate during storage. In contrast to the common practice of postharvest application of growth regulators, we have studied the effect of pre-harvest application of the ethylene biosynthesis inhibitor, viz. salicylic acid (SA) at three different concentrations (75, 150 and 200 ppm) on ‘Amrapali’ mango fruits. The results indicate that pre-harvest application of salicylic acid, one week before the commercial harvest could effectively modulate the postharvest behaviour of the mango fruits during storage at ambient conditions (30 ± 5°C and 50 ± 5% RH). Although the mango was responsive to all the treatments, SA (200 ppm) was found to be effective in delaying the ripening cum senescence processes through suppression of respiration rate (105.43 ml CO2 kg−1h−1) and ethylene production rates (0.20 μl C2H4 kg−1 h−1) and retention of high firmness (21.76 N), colour (26.31 ΔE), TSS (27.72°B) and titratable acidity (0.53%) compared to untreated fruits.

Differential Gene Expression Studies: A Possible Way to Understand Bearing Habit in Fruit Crops

India is still by far the major producer of various fruit crops, but its relative share in the world production has been gradually declining. Alternate bearer fruit cultivars present a serious economic problem to fruit growers. An alternate bearing plant is the one that does not bear a regular crop year-after-year; rather heavy yields are followed by extremely light yield. This complex phenomenon could be solved by transcriptome analysis resulted in numerous differentially expressed genes (DEGs), allowing the partial identification of mechanisms that convert ‘on’ into ‘off’ buds. Several candidate genes would be identified in future studies whose differential expression can be correlated with growth habit and architectural variation in another perennial fruit crops. The information generated will be utilized for identification of potential parents, desired hybrids in early nursery stage, thus would assist breeders by bringing precision breeding and also make available fruits during off years.

An efficient and rapid method for the isolation of RNA from different recalcitrant tissues of mango (Mangifera indica L.)

Summary The isolation of high quality RNA from different tissues of mango (Mangifera indica L.) is relatively challenging due to the presence of interfering substances such as polysaccharides, polyphenols, and proteins. All these compounds render available isolation protocols useless by reducing the quality (purity and integrity) and quantity of the RNA that can be recovered. Several tissue-specific protocols for the isolation of RNA have been developed specifically for mango, however they are cumbersome, expensive and time-consuming. To overcome these drawbacks, we have developed a comprehensive (CTAB-free, guanidine-free, and LiCl-free) RNA isolation protocol using SDS (sodium dodecyl sulphate) plus phenol which works well for most mango tissues such as leaves, flowers, and fruit, at different stages of development or ripening, as well as fruit peel and seed kernels.This rapid protocol allowed us to process large numbers of samples (12 - 15) simultaneously in a single day. Using this method, we obtained good quantity RNA (16 - 80 ?g g-1 tissue) from various mango tissues at different stages of development. RNA isolated by this method was pure and amenable to various downstream molecular applications such as RT-PCR and the construction of a cDNA library.

Studies on extent of polyembryony in salt tolerant mango rootstocks

The present study was undertaken to know the extent of polyembryony in three mango rootstocks, namelyOlour, Kurukkan and 13-1. Freshly harvested seeds after 10 days were sown in earthen pots (sand: soil: FYM; 1: 1: 1). The number of seedlings from stones of Olour, Kurukkan and 13-1 were recorded and extent ofpolyembryony was calculated. The extent of polyembryony was maximum in Kurukkan (74.43%) followed by 13-1(51.85%) and Olour (33.15%). The number of seedlings per stone ranged from 1 to 5 in Olour & Kurukkan; and1 to 4 in 13-1 rootstock. The average number of seedlings per stone was maximum in Kurukkan (2.35) followed by 13-1 (1.88) and Olour (1.51).