Soliton attenuation and emergent hydrodynamics in fragile matter

Disordered packings of soft grains are fragile mechanical systems that loose rigidity upon lowering the external pressure towards zero. At zero pressure, we find that any infinitesimal strain-impulse propagates initially as a non-linear solitary wave progressively attenuated by disorder. We demonstrate that the particle fluctuations generated by the solitary-wave decay, can be viewed as a granular analogue of temperature. Their presence is manifested by two emergent macroscopic properties absent in the unperturbed granular packing: a finite pressure that scales with the injected energy (akin to a granular temperature) and an anomalous viscosity that arises even when the microscopic mechanisms of energy dissipation are negligible. Consistent with the interpretation of this state as a fluid-like thermalized state, the shear modulus remains zero. Further, we follow in detail the attenuation of the initial solitary wave identifying two distinct regimes : an initial exponential decay, followed by a longer power law decay and suggest simple models to explain these two regimes.Comment: 8 pages, 3 Figure

An appraisal of ginger (Zingiber officinale Rosc.) production in Sikkim, India

A general description of Sikkim and various aspects of cultivation and marketing of ginger (Zingiber officinale) in the state are discussed. The trend in production and major constraints in productivity are also dealt with. &nbsp

Pearl millet germplasm at ICRISAT genebank - status and impact

Pearl millet (Pennisetum glaucum) is an important food and forage crop in Africa and Asia, and forage in Americas. It is probably the world’s hardiest crop and has great potential because of its suitability to the extreme limits of agriculture. It is mainly cultivated in Niger, Nigeria, Burkina Faso, Togo, Ghana, Mali, Senegal, Central African Republic, Cameroon, Sudan, Botswana, Namibia, Zambia, Zimbabwe and South Africa in Africa; and India, Pakistan and Yemen in Asia. The success in crop improvement programs depends largely on the extent of genetic variability available to the researchers. Pearl millet is endowed with enormous genetic variability for various morphological traits, yield components, adaptation and quality traits. In ensuring that the plant breeders will have genetic resources for use in plant breeding programs, collection, conservation, characterization, evaluation, documentation and distribution of plant genetic resources is very important. Large efforts were made to collect and conserve the pearl millet diversity before it is lost forever. In this article, we have summarized the current status of pearl millet germplasm assembled in the genebank at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) and discussed its impact

Patterns of diversity in pigeonpea (Cajanus cajan (L.) Millsp.) germplasm collected from different elevations in Kenya

Pigeonpea germplasm accessions collected from low (1500 m) of Kenya were evaluated for 15 agronomic traits and seed protein content at ICRISAT, Patancheru, India. There were significant differences (P < 0.001) among elevation zones for the number of primary and secondary branches, days to 75% maturity, pod length, seeds per pod, 100-seed weight and seed yield. Mean values indicated that the accessions from low elevation zone were significantly different from those collected in higher elevation zones for early flowering and maturity, number of primary branches, pod length, number of pods per plant, seeds per pod, 100-seed weight, seed yield and harvest index. None of the accessions collected in Kenya belonged to extra early (<80 days to 50% flowering) and early (80–100 days to 50% flowering) maturity groups, as defined by time to flowering at Patancheru, India. Mean diversity index based on all characters indicated that accessions from the low elevation zone are more diverse than those from the higher elevation zones. Frequency distribution for trait extremes indicated that the accessions from the low elevation zone were early to flower and mature, short statured, produced more primary and secondary branches with high pod bearing length, long pods, more pods per plant, more seeds per pod, a high seed yield and harvest index. Accessions from the very high elevation zone were late flowering, with a large number of tertiary branches, large seeds and a high shelling percentage and could be a source for cold tolerance and the breeding of vegetable types. Results suggest that the elevation of collection sites is therefore a very important determinant of variation patterns of pigeonpea in Keny

Groundnut Cultivar Nyanda (ICGV 93437) Released in Zimbabwe

Nyanda (ICGV 93437) is a new Spanish groundnut breeding line developed at the International Crops Research Institute for the Semi-Arid Tropics, Patancheru, Andhra Pradesh, India, during the 1990s. It was released in Zimbabwe in 2001 for commercial cultivation. It was derived from the cross between two early maturing advanced breeding lines ICGV 86063 and ICGV 86065. Nyanda produces 13.5% higher yield than the popular cultivar Falcon. It matures 6 days earlier than Falcon and is almost similar to Falcon in shelling outturn and seed size. Nyanda has erect growth habit, sequential branching pattern and green plant colour. Data on various morphological, agronomic and seed quality traits are tabulated

Identification and evaluation of chickpea germplasm for tolerance to heat stress

Global warming and extreme temperatures are predicted in the future, hence identifi cation of appropriate varieties that could adapt to such changes is imperative for sustaining crop productivity. Thirty-fi ve early maturing chickpea (Cicer arietinum L.) germplasm accessions were evaluated for their tolerance to heat stress. Plant traits such as plant width, fl owering duration, days to maturity, pod number, seed weight, grain yield and per-day productivity were affected under heat stress. Genotypes differed in their sensitivity to heat stress, and the yield loss among genotypes varied from 10 to 15% of potential yield for every degree increase in temperature beyond the optimum temperature range. Multiple regression analysis indicated that the plant trait expression can be predicted accurately for the assumed change in climate on the basis of mean temperature, daylength, duration of bright sunshine, incident solar radiation, relative humidity, wind velocity, and potential evaporation. Mitigation of heat stress by irrigation and application of additional nitrogen to the crop resulted in sustaining the potential yield (up to 80%). ICC 14346 showed high tolerance to heat stress and could be used as a parent in crop improvement research. ICC 5597, ICC 5829, ICC 6121, ICC 7410, ICC 11916, ICC 13124, ICC 14284, ICC 14368, and ICC 14653 were heat stress tolerant, responsive to irrigation and nitrogen management, and consistently high yielding (>1400 kg ha–1) compared with the control ICCV 92944 (1333 kg ha–1)

Mini Core Collections for Enhanced Utilization of Genetic Resources in Crop Improvement

Plant genetic resources form the raw material for developing high yielding cultivars. About 7.4 million accessions of various economically important crops have been conserved globally. Since the large size of germplasm collections hampers the assessment of their genetic worth, the ‘mini core collection concept’ was postulated and developed at ICRISAT. The mini core serves as an efficient and convenient option for assessment of genetic diversity, population structure, association mapping and targeted allele mining for agronomically important traits and acts as a gateway to the germplasm. Using the mini core collection approach, scientists at ICRISAT and in national programs have identified diverse sources of resistance/tolerance for many biotic and abiotic stresses, and for agronomic and quality traits in chickpea, groundnut, pigeonpea, sorghum, pearl millet, foxtail millet and finger millet. This is expected to enhance the use of germplasm in crop improvement. Molecular characterization of the mini core will further enhance its use in plant breeding programs

Identification of Large-Seeded High-Yielding Stable Kabuli Chickpea Germplasm Lines for Use in Crop Improvement

Seed size is an important trait in kabuli chickpea (Cicer arietinum L.). The kabuli chickpeas with a 100-seed weight of >40 g garner higher market price as they are preferred by consumers. The objective of this study was to evaluate a sample of chickpea landraces, breeding lines, and cultivars for morphological traits and yield and identify lines that are high yielding and exhibit stable performance across environments. We evaluated 65 large-seeded kabuli lines identifi ed from the ICRISAT germplasm collection in three sets, 18 trials, and 13 environments for 22 qualitative and quantitative traits. Several highly signifi cant correlations were observed in all three sets and a few large-seeded high-yielding lines with stable yield were selected. Two extralarge- seeded (100-seed weight > 50 g) lines ICC 17109 (Blanco Sinaloa 92), a breeding line, and ICC 17452 (CuGa 288), a landrace, both originating from Mexico showed high yield potential and were moderately stable across environments. The small-seeded control cultivars, though high yielding, were highly unstable, performing better only in favorable environments. The study has also shown that some vegetative characteristics were more sensitive to stress than yield and yield components, hence selection in unfavorable environments should be based on grain yield and its components

Evaluation of pollination control methods for pigeonpea (Cajanus cajan (L.) Millsp.) germplasm regeneration

Maintaining the genetic integrity of germplasm accessions during regeneration is of paramount importance in ex situ conservation of plant genetic resources. In pigeonpea (Cajanus cajan (L.) Millsp.) where outcrossing by insects ranges from 3 to 26% (Reddy et al. 2004), regeneration is costly in terms of time and resources (Remanandan et al. 1988). The problems are compounded when several hundred germplasm accessions need to be regenerated in a season. Nestor and Ramanatha Rao (1998), analyzing the information on seed germplasm regeneration, noted much conjecture and uncertainty over regeneration procedures employed by genebanks. Therefore, the development of optimal procedures for regeneration, to preclude contamination of pollination, is vital to maintain genetic integrity of pigeonpea accessions..

Developing a core collection of peanut specific to Valencia market type

Crop improvement and the dissection of complex genetic traits require germplasm diversity. A core collection is a gateway for the use of diverse accessions with benefi cial traits in applied breeding programs. Valencia germplasm consisting of 630 peanut (Arachis hypogaea L. ssp. fastigiata var. fastigiata) accessions from the USDA collection and a check cultivar, New Mexico Valencia C, were evaluated for 26 descriptors in an augmented design for two seasons. The accessions were stratifi ed by country of origin, and data on morphological and agronomic descriptors were used for clustering following Ward’s method. About 10% or a minimum of one accession from each cluster and region were selected to develop core subset of 77 accessions. Comparison of means between the core subset and the entire collection indicated that the genetic variation available for these traits in the entire collection has been preserved in the core subset. The similarity in correlation coeffi cients in the entire collection and core subset suggests that this core subset has preserved most of the coadapted gene complexes controlling these associations. Peanut breeders engaged in improving the genetic potential of Valencia peanuts will fi nd this core subset useful in cultivar development