Influence of AM fungi,inorganic phosphorus and irrigation regimes on plant water relations and soil physical properties in okra (Abelmoschus esculentus L.) – pea (Pisum sativum L.) cropping system in Himalayan acid alfisol

Present investigation studied plant water relations and soil physical properties through AM fungi (Glomus mosseae) to mitigate drought stress in Himalayan acid Alfisol having low water retentivity. Experimentation was carried out at Palampur, India during 2009–2011 in okra–pea cropping system in randomized block design (RBD) replicated thrice with 14 treatments comprising arbuscular mycorrhizal (AM) fungi, varying phosphorus nutrition and irrigation regimes at 40 and 80% available water holding capacity. Integrated use of AM fungi at varying phosphorus (P) levels and irrigation regimes led to significantly higher relative leaf water content (3% each) in okra and pea besides significantly higher xylem water potential (27%) in pea over non-AM fungi counterparts. AM fungi enhanced water-use-efficiency in okra (5–17%) and pea (12–35%) over non–AM fungi counterparts. AM fungi also improved water holding capacity (5–6%) and mean weight diameter of soil particles (4–9%) over non–AM fungi counterparts; but, had nominal or no effect on bulk density. Mycorrhizal plants maintained higher tissue water content imparting greater drought resistance to plants over non–mycorrhizal plants at moisture stress. It is inferred that integrated application of AM fungi and P at varying irrigation regimes improved the plant water relations vis-à-vis drought resistance, crop productivity, WUE, soil aggregation and water holding capacity in okra–pea sequence in Himalayan acid Alfisol.     

Agronomic bio-fortification and quality enhancement in okra–pea cropping system through arbuscular mycorrhizal fungi at varying phosphorus and irrigation regimes in Himalayan acid alfisol

A field experimentation was conducted during 2009-2011 at CSK Himachal Pradesh Agricultural University, Palampur, India characterized with wet-temperate climate and acid Alfisol soil having medium available phosphorus content. The study aimed at bio-fortification and quality enhancement of okra (Abelmoschus esculentus)–pea (Pisum sativum) cropping system through arbuscular mycorrhizal fungi (AMF) (Glomus mosseae) at varying inorganic phosphorus (50, 75, and 100% soil-test-based recommended P dose) and irrigation regimes (40 and 80% available water capacity) in a Himalayan acid Alfisol. The results revealed that AMF and inorganic P significantly enhanced the concentrations and uptake of various primary [nitrogen (N), phosphorus (P), and potassium (K)]; secondary [calcium (Ca)]; and micronutrients [iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), boron (B), and molybdenum (Mo)] in okra and pea crops. However, effects of varying irrigation regimes were found to be nominal. In okra, AMF inoculation considerably enhanced N, P, K, B, and Mo uptake by 5, 19, 3, 4, and 15%, respectively, over their non-AMF counterparts. Likewise in pea, a higher amount of N (10%), P (26%), K (7%), Fe (7%), Cu (38%), Zn (20%), Mn (4%), B (7%), and Mo (13%) uptake was registered through AMF inoculation over their non-AMF counterparts. Application of soil-test-based P dose from 50% to 100% P also resulted in significant and consistent improvement in N, P, K, B, and Mo uptake both in okra and pea and in Zn, Cu, Mn, and Fe uptake in pea crop. Magnitude of increase in Ca content was to the tune of 13 and 4%, respectively, in okra fruits and pea pods following AMF inoculation, whereas crude protein content enhanced by 4% each in both the crops. Overall, the current study demonstrates the important role of AMF in nutrient enrichment and quality enhancement of okra and pea crops in acid Alfisol, besides considerable reduction in investment on chemical fertilizers. Results of current study suggest that AMF use in Himalayan production systems is of tremendous significance to harvest nutritionally-rich farm produce for Himalayan communities suffering from malnutrition especially anemia and Zn deficiency, and equally to resource-poor Himalayan farmers who ill-afford expensive external inputs.     

Tripartite symbiosis of Pisum–Glomus–Rhizobium leads to enhanced productivity,nitrogen and phosphorus economy,quality, and biofortification in garden pea in a Himalayan acid Alfisol

The present study was carried out to assess nitrogen (N) and phosphorus (P) economy, quality, and productivity of garden pea (Pisum sativum L.) through dual-inoculation of arbuscular mycorrhizal fungi (AMF) and Rhizobium in an acid Alfisol. Experiment was laid out in randomized block design replicated thrice comprising 13 treatments viz. Rhizobium along with three graded N levels (25%, 50%, and 75% soil-test-based recommended N), AMF along with three graded P levels (25%, 50%, and 75% soil-test-based recommended P), dual-inoculation of AMF and Rhizobium conjoint with four graded N and P levels (25%, 50%, 75%, and 100% soil-test-based recommended N and P), and three other treatments viz. generalized recommended NP potassium (K) dose (GRD), farmers' practice, and absolute control. The results revealed that dual-inoculation of AMF and Rhizobium enhanced the pea productivity, macronutrient (NPK) and micronutrient iron, copper, zinc, and manganese (Fe, Cu, Zn, and Mn) concentrations, and their uptake besides enhancing garden pea quality. Also, dual-inoculation of both symbionts at 75% and 100% soil-test-based N and P dose behaved statistically alike with respect to pea pod yield, NPK uptake, and quality parameters like total soluble solids (TSS) and crude protein (CP), thus indicating an economy of about 25% soil-test-based N and P dose through co-inoculation. AMF and Rhizobium dual-inoculated treatments led to enhanced TSS and CP in pea pods by 4.2% and 6.2%, respectively, over GRD, while sole application of AMF- or Rhizobium-imbedded treatments could enhance these quality parameters by 2.1% only in each case. Similarly, the highest N and P response ratio was registered in dual-inoculated treatments. Overall, dual-inoculation of AMF and Rhizobium with 75% soil-test-based N and P dose in pea can save up to 25% fertilizer N and P dose in acid Alfisol.Also, this tripartite symbiosis besides enhancing pea quality led to better bio-fortified pea seeds with micronutrients especially Fe and Zn, which can greatly curtail the widespread anemia and Zn deficiency in humans living in Himalayan acid Alfisol.     

Influence of Inorganic Phosphorus,VAM Fungi,and Irrigation Regimes on Crop Productivity and Phosphorus Transformations in Okra (Abelmoschus esculentus L.)–Pea (Pisum sativum L.) Cropping System in an Acid Alfisol

The present investigation was carried out at CSK Himachal Pradesh Agricultural University, Palampur, India, during 2009–2011 to economize inorganic phosphorus (P) and water needs of an okra (Abelmoschus esculentus)–pea (Pisum sativum) cropping system through vesicular arbuscular mycorrhizal (VAM) fungi (Glomus mosseae) in a Himalayan acid Alfisol. The field experiment was replicated three times in a randomized block design comprising 14 treatments consisting of 12 treatment combinations of two VAM levels [0 and 12 kg ha^?1], three phosphorus levels [50, 75, and 100% of recommended soil-test-based nitrogen (N)–P–potassium (K)], and two irrigation regimes [40 and 80% of available water-holding capacity of field soil (AWC)], in addition to one treatment with “generalized recommended NPK dose with generalized recommended irrigations (GRD)” and one treatment based on “farmers’ practice of plant nutrition and irrigation management in the region.” This article presents crop productivity and P dynamics studies during the second crop cycle of okra–pea sequence (2010–2011) and statuses of different P fractions in the soil after the second pea crop harvest during 2010–2011. Crop productivity and P uptake data in okra–pea sequence indicated that application of VAM + 75% P dose at either of two irrigation regimes did not differ significantly than GRD treatment and VAM + 100% P dose. It suggests an economy of about 25% inorganic P dose through VAM fungi. The treatments imbedded with VAM inoculation enhanced the P uptake in okra–pea system, on an average by 21% over the GRD and non-VAM-inoculated counterparts. Further, integrated application of P, VAM, and irrigation regimes evaluated in okra–pea sequence for 2 years led to greater status of water-soluble P (21%), sodium bicarbonate (NaHCO₃)–inorganic phosphorus (Pi) (11%), sodium hydroxide (NaOH)–Pi (9%), hydrochloric acid (HCl)–extractable–P (20%) over non-VAM-inoculated counterparts and low status of organic P (NaHCO₃-P_o and NaOH-P_o), all of which appreciably contributed to available P supply to plants in the present study in an acid Alfisol. The correlation coefficient reveals that contribution of inorganic P forms is highly correlated to crop productivity and total P uptake in okra and pea crops besides soil available P in the present study. Overall, it is concluded that VAM inoculation in okra–pea cropping system significantly enhanced the P availability to plants by way of enriching the labile-P pool such as water-soluble P and P loosely bound to aluminium (Al-P) and iron (Fe-P) on adsorption complexes and by P mineralization from organic matter in an Himalayan acid Alfisol.     

Genetic diversity in local cultivars of garden pea (Pisum sativum L.) conserved ‘on farm’ and in historical collections

During a national Swedish collection mission of vegetable varieties conserved ‘on farm’ more than 70 pea accessions were obtained, many of which had been grown locally for more than 100 years. In spite of a likely origin in the multitude of obsolete commercial pea varieties available on the Swedish seed market in the nineteenth century, the rediscovered local cultivars have lost their original names and cultivar identity while being maintained ‘on farm’. To analyze genetic diversity in the repatriated material, 20 accessions were genotyped with twelve SSR markers and compared with 15 obsolete cultivars kept in genebanks and 13 cultivars preserved as non-viable seeds collected in 1877–1918. Most of the local cultivars were genetically distinct from each other, and in only a few cases could a possible origin in a tested obsolete cultivar be suggested. These results reflect the wide diversity of pea cultivars present in Sweden during the nineteenth century. Both between and within accession genetic diversity was larger among the historical samples of obsolete cultivars compared to local cultivars and cultivars preserved in genebanks, indicating genetic erosion over time both in genebanks and during conservation ‘on farm’. The constraints on identifying and verifying historical cultivars using genetic markers are discussed.     

Broad antifungal activity of β-isoxazolinonyl-alanine,a non-protein amino acid from roots of pea (Pisum sativum L.) seedlings

Summary -(Isoxazolin-5-on-2-yl)-alanine (IA), a heterocyclic non-protein amino acid from root extracts and root exudates of pea seedlings, acts as a potent growth inhibitor of several eukaryotic organisms, including yeasts, phytopathogenic fungi, unicellular green algae, and higher plants. The antibiotic effect on baker's yeast was reversed by l-methionine, l-cysteine, and l-homocysteine. Phytopathogenic fungi such as Botrytis cinerea, Pythium ultimum, and Rhizoctonia solani grown on agar containing IA were inhibited in the growth of mycelia or in the production of sclerotia. In contrast, no significant inhibition of either Gram-positive or Gram-negative bacteria was observed. Rhizobium leguminosarum, the compatible microsymbiont of Pisum spp., and Rhizobium meliloti were able to tolerate up to 2.9 mM IA (500 ppm) without any effect on the growth rate. Bradyrhizobium japonicum even gave a positive chemotactic response to IA. The ecological significance of IA as a preformed plant protectant during the seedling stage of Pisum spp. and other IA-containing legumes is discussed.