The productivity gains in the cultivated Vigna (notably Green gram and black gram) over the last 7 decades in India have been around 100%. Breeders have been successful in significantly reducing the maturity duration and disease resistance (MYMV). However, the yield potential of the newly developed improved varieties have remained almost the same. Whether the productivity gains should be ascribed to replacement of MYMV susceptible older varieties with those of newer MYMV resistant varieties, to adoption of improved cultural practices or a combination of both?? If a combination of both, then what should be the proportional contribution???
Some of the gains over 7 decades would be due to the increase in CO2 in the atmosphere. Possibly 25% or so.
Gains are due to the new approaches in crop improvement and management practices
Many experiments done by plant breeders and agronomist suggest that gains in historic production levels are equally grounded in the agronomic practices which can be deemed as environment and the genetics or varietal improvement. Breeding programs need to focus on yield quality and defensive characteristic. For high yield potential the factors such as lack of water and nutrition need to be eliminated and for defensive characters the plants need to be exposed to both biotic and abiotic stresses. Many of our soils have lost significant amounts of soil organic matter and may not be of best pH the enhancement and optimization of these factors will help identify high yield capacity. For defensive characters the use of genetic blends of mixed varieties can be useful as well as development of less uniform genetic approaches. If plants are put into rotations it can enhance the yield environment and in plants grown continually the pests and diseases inhabitating the soil environment can be optimized for their effects allowing resistance sources to be expressed in the severe environment. In the case of vigna the genetics of symbiotics organisms the Rhizobium nitrogen fixers and the root extending mycorrhizal fungi may alse need consideration. For foliar diseases the use of disease spreaders and favorable disease environments can be supported
I do agree with Paul's opinion that productivity gain in Vigna may be apportioned equally to improved genetic potential of varieties and adoption of better agronomic practices. For further productivity gain, genetic diversity has to be enhanced. High throughput testing methods are required to enhance selection efficiency. Moreover, testing of germplasm in condition to which selections are destined to be grown commercially is also equally important.
We cannot ignore the contribution of the increased CO2 in the atmosphere. A paper in Nature attributed 30% of the current world biomass production to the extra CO2.
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