Management and cultivar effects on ruminant nutritional quality of pearl millet (Pennisetum glaucum (L.) R. Br.) stover: II. Effects of cultivar choice on stover quality and productivity
Introduction
One of the most effective and least-cost options open to farmers to increase both stover productivity and stover quality is the choice of cultivar, provided that there are significant differences among cultivars for both productivity and quality, and that emphasizing stover traits does not carry an unacceptable penalty in terms of reduction in grain yield. In addition, there may be potential synergies between higher input management and superior cultivars that can be exploited by farmers to maximize both stover production and quality. There are major benefits to farmers in both greater stover yields and improved stover quality, whether the stover is used for maintaining draft or meat animals, for the production of milk for sale, or for direct sale in peri-urban markets, where there is a high demand by urban milk producers for good quality stover. For example, for sorghum stover, which is intensively traded in the peri-urban urban dairy environment in Hyderabad in India, cultivar-dependent variation in stover in vitro digestibility of 5 units (46–51%) resulted in a 25% price difference (3 compared to 4 Indian Rupees) per kilogram dry sorghum stover (Blümmel and Rao, 2006).
A high demand for quality stover, and a consequently growing economic value (Kelley and Rao, 1996), has resulted in cereal breeding programs beginning to focus on the improvement of stover yield and quality as well as grain yield (Reddy et al., 1995, Hash et al., 2000). The ultimate success of crop breeding programs targeting increases in stover yield and improvement in stover quality depends on the existence of useful genetic variation in stover quantity and quality, and on the absence of competitive relationships between these and other desirable agronomic traits such as grain yield. Estimates based on ex ante impact assessments predict that improvement of stover quality through genetic enhancement can result in benefit:cost ratios of 15:1 and higher (Kristjianson and Zerbini, 1999), so the potential gains are real, if the conditions for simultaneous improvement in grain and stover are met.
The previous paper from this study (Bidinger and Blümmel, 2007) examined the effects of crop management variables on stover and grain productivity and stover quality in pearl millet. The objective of this part of the study was to assess (1) the range of variation among existing cultivars in both stover productivity and quality, (2) the relationship of these with each other and with grain yield, and the (3) effects of management variables on these relationships. In addition to quantifying the potential benefits of cultivar choice, the results of this study also have important implications for the future genetic improvement of stover quality of pearl millet.
Section snippets
Cultivars used
The material used in the experiment represent diverse cultivar types adapted to the major arid and semi-arid pearl millet growing zones of NW India, primarily the state of Rajasthan and adjacent areas of the states of Haryana and Gujarat, in which pearl millet stover is widely used to feed domestic animals. They included (1) five representatives of traditional landraces, (2) six representatives of genetically improved dual-purpose (grain and stover) open-pollinated varieties with different
Cultivar differences in stover productivity and quality
There were highly significant differences among cultivars for all productivity and quality variables measured in the experiment (Table 1). However, the presence of significant interactions of cultivar and year for total stover yield, and for most stover quality parameters, indicate that cultivar differences are not independent of environmental differences among years. Similarly, there were significant cultivar × fertility interactions for biomass, grain and all measures of stover yield; cultivar ×
Summary
Dual-purpose cultivars can be developed by essentially two approaches, namely by exploiting variation in already existing genotypes and by targeted further genetic enhancement. The first approach is quick and does not need much investment, since only screening of genotypes for stover quantity and quality is required. The second is a long-term approach and does require some investment; but there is an excellent potential to improve dual-purpose traits above their current level. However, certain
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