Out of 26 strains of Volvariella volvacea used, 18 were of 'typical' type and possessed all the characteristics of a normal V. volvacea mycelium, while the rest 4 'atypical' type strains showed completely distinct mycelial growth characteristics. The remaining 4 strains grew very slowly and exhibited growth characteristics of single spore isolates of V. volvacea. Strains varied in their extracellular lignocellulolytic activities and strains; OE-274, OE-272 and OE-210 with high ligninase enzymes (laccase and polyphenol oxidase) activities, gave highest mushroom yield on pasteurized paddy straw substrate. On the composted paddy straw substrate, additional two strains, OE-213 and OE-215 with lower activities of ligninases also gave higher mushroom yield. Mushrooms were harvested 3 to 4 d early from the composted substrate than on the pasteurized substrate. Activities of endoglucanase, laccase and polyphenol oxidase were found to be more crucial for mushroom yield on pasteurized substrate, while xylanase and β-glucosidase were more important for composted substrate. Strains also varied in their fruiting bodies quality and the substrate used for mushroom cultivation also affected the fruiting body quality. The superior yielding strains varied in shape, size, weight, colour and contents of sodium and potassium in their fruiting bodies; while contents of carbon, calcium and protein did not vary much with the strains.

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Plant microbiome also known as it's second or extended genome, regulates and influences plant's metabolism and growth. The plant microbiome members promote nutrient uptake, tolerance against abiotic and biotic stresses and regulate host immune system. Although there is plenty of information available on role of rhizosphere microbiome for plant growth, but still there is dearth of knowledge for the vast majority of rhizosphere microorganisms. This is mainly due to their unknown growth requirements or inability to grow on any known growth media. To support plant growth under stress conditions, the information on presence of specific microorganism in rhizosphere microbiome along with the role it plays is very much essential. Here, we review the generalized role of plant microbiome in different plant functions, information generated till date specifically on wheat metagenomics, role of rhizosphere microorganisms in abiotic stress management in other crop plants and the breeding in wheat in light with wheat metagenomics or metagenome engineering through breeding.

Wheat (Triticum aestivum L.) cultivation differs considerably in respect of soil type, temperature, pH, organic matter, moisture regime, etc. Among these, rising atmospheric temperature due to global warming is most important as it affects grain yield drastically. Studies have shown that for every 1°C rise in temperature above wheat's optimal growing temperature range of 20-25°C, there is a decrease in 2.8 days and 1.5 mg in the grain filling period and kernel weight, respectively, resulting in wheat yield reduction by 4-6 quintal per hectare. Growing demand for food and multidimensional issues of global warming may further push wheat crop to heat stress environments that can substantially affect heading duration, percent grain setting, maturity duration, grain growth rate and ultimately total grain yield. Considerable genetic variation exists in wheat gene pool with respect to various attributes associated with high temperature and stress tolerance; however, only about 15% of the genetic variability could be incorporated into cultivated wheat so far. Thus, alternative strategies have to be explored and implemented for sustainable, more productive and environment friendly agriculture. One of the feasible and environment friendly option is to look at micro-organisms that reside inside the plant without adversely affecting its growth, known as 'endophytes', and these colonize virtually all plant organs such as roots, stems, leaves, flowers and grains. The relationship between plant and endophytes is vital to the plant health, productivity and overall survival under abiotic stress conditions. Thus, it becomes imperative to enlist the endophytes (bacterial and fungal) isolated till date from wheat cultivars, their mechanism of ingression and establishment inside plant organs, genes involved in ingression, the survival advantages they confer to the plant under abiotic stress conditions and the potential benefits of their use in sustainable wheat cultivation.

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Of the 2 parent strains and 6 single-spore isolates (SSIs) used in this study, the SSIs BBSR-007 and BBSR-002 of the culinary-medicinal straw mushroom Volvariella volvacea exhibited superior growth characteristics on different growth media. These also took less time until first harvest (days after spawning), gave higher numbers of fruiting bodies per unit weight of substrate, and provided a higher mushroom yield on composted substrate. The fruiting body weight of isolate BBSR-007 was significantly higher compared to BBSR-002. On pasteurized paddy straw, the SSI BBSR-007 had a higher mushroom yield than BBSR-002. The contents of dry matter, protein, and other elements (sodium, potassium, and calcium) were on par in both the parent strains and different SSIs, except SSI OE-55-08, which had highest dry matter, protein content, and potassium/-to-odium ratio. In amplified ribosomal DNA restriction analysis, the SSIs did not show any distinctness, whereas in amplified fragment length polymorphism, the SSI OE-55-08 of parent strain OE-55 formed a separate clade; of 4 SSIs of strain OE-274, the SSI BBSR-003 formed a separate clade than other SSIs. The genetically distinct SSI OE-55-08 produced the highest numbers of fruit bodies per unit weight of substrate and exhibited the highest amounts of dry matter and protein in its fruit bodies. Another slightly distinct SSI, BBSR-003, formed white aerial mycelia on growth substrate, and its fruit bodies exhibited the highest levels of sodium and calcium.

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