(a) Nilgiris (b) Western Ghats (c) Eastern Gnat (d) Kankan Coast.
(ix) Which of the following is a commercial crop?
(a) Wheat
Cotton (c) Corn (d) Rice
(x) The fundamental Rights in our constitution are inspired by the constitution of
(a) UK (by USA (c) USSR (d) Sweden
- Fill up the blanks with appropriate word:-
(i) in Germany - - were killed in chamber poisonous gases.
(ii) Economic activities are classified into 2.- categories.
(iii) A total of - Schemes of pollution abatement abatement has been sanctione
schemes have completed at the Ganga action plan
(iv) Voting of the Estates General was conducted on the principle of -
v) Socialists regarded
as the root of all evils in society.
State whether the following statements are True or False
i) Charles Darwin gave the theory of "survival of the fittest".
i) There are seven major tectonic plates.
(True/False)
(True/False)
1:1
infallic
form of recipitation
Answers
Answer:
Global food demand is expected to nearly double by 2050 due to an increase in the world's population. The Green Revolution has played a key role in the past century by increasing agricultural productivity worldwide, however, limited availability and continued depletion of natural resources such as arable land and water will continue to pose a serious challenge for global food security in the coming decades. High yielding varieties with proven tolerance to biotic and abiotic stresses, superior nutritional profiles, and the ability to adapt to the changing environment are needed for continued agricultural sustainability. The narrow genetic base of modern cultivars is becoming a major bottleneck for crop improvement efforts and, therefore, the use of crop wild relatives (CWRs) is a promising approach to enhance genetic diversity of cultivated crops. This article provides a review of the efforts to date on the exploration of CWRs as a source of tolerance to multiple biotic and abiotic stresses in four global crops of importance; maize, rice, cotton, and soybean. In addition to the overview of the repertoire and geographical spread of CWRs in each of the respective crops, we have provided a comprehensive discussion on the morphological and/or genetic basis of the traits along with some examples, when available, of the research in the transfer of traits from CWRs to cultivated varieties. The emergence of modern molecular and genomic technologies has not only accelerated the pace of dissecting the genetics underlying the traits found in CWRs, but also enabled rapid and efficient trait transfer and genome manipulation. The potential and promise of these technologies has also been highlighted in this review.
Keywords: crop wild relatives (CWRs), maize, rice, cotton, soybean, tolerance to biotic stress, tolerance to abiotic stress
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Introduction
Understanding the origins of crop plants and their relationships to wild relatives has been a major focus for plant biologists for many years. This knowledge continues to be of great importance in dissecting the process of crop domestication and the ability to leverage wild relatives for crop improvement. Germplasm characterization studies and breeding programs over decades have shown that cultivated plants, in general, have a relatively lower level of tolerance to biotic and abiotic stresses when compared to crop wild relatives (CWRs). One-dimensional selection for increased yield has been hypothesized to result in metabolic resource allocation toward accelerated growth and reproduction and away from plant's tolerance to biotic and abiotic factors (Rosenthal and Dirzo, 1997). Alternatively, plant breeders and population geneticists believe that artificial selection for very small percentage of genes has created breeding bottlenecks that has drastically reduced genetic variation of modern crops and led to the loss of genes derived from CWRs (Hufford et al., 2012). Although tolerance genes have traditionally been considered as negatively correlated with yield (Strauss et al., 2002; Wise, 2007), it has been recently reported that breeding for multiple plant defense traits can be achieved without compromising crop yield (Kaplan et al., 2009).
CWRs offer a diverse array of traits with the potential to decrease the amount of yield loss as a result of biotic and abiotic stresses and pest damage. These CWR- derived resistant traits could be brought into susceptible modern crops through conventional breeding (if there is a sexual compatibility), transgenesis, or other emerging technologies. Introgression of traits of interest from a CWR to a sexually compatible conventional line through traditional breeding could add complications due