this file is about Cultural, physiological and molecular approaches to the improvement of economic plants for better yield of economic products

1. by
MUHAMMAD USMAN ZAKI(Roll no.05)

2. 

3. 
Cultural approaches
Physiological approaches
Molecular approaches
CONTENTS

4. 
Crop yield is controlled by the interaction between the genetic
potentialities of crop plants and the environment in which they grow.
Variations in the genotype and in the environment, including weather and
cultural practices, act through physiological processes to control growth.
Thus the physiological processes of plants are the machinery through
which both the genetic potentialities and the environment operate to
produce the quantity and quality of growth or phenotype which we term
yield.
Introduction

5. 
 Planting Patterns
 Tillering
 Rooting Patterns
 utilization of the growing season
 Ideotypes
 Double Cropping
Cultural approaches

6. 
 the potential loss of yield caused by lack of uniformity and the need for increased uniformity as
plant populations increase. Some preventable causes of non uniformity are obvious. Seeds
should be uniform in germination time and should be planted uniformly. At critically high
planting rates any lack of uniform plant distribution would mean localized high density areas
where plants would be shaded past the point of instability at which some plants must be
suppressed no matter how uniform the initial conditions. The adverse effect of any lack of
uniformity would be accentuated.
Tillering
 The disturbing fact is that tillering plants such as wheat [Triticum (aestivum L.) sp.] or rice
(Oryza sativa L.) are essentially plants growing in multiple-plant hills which is, according to our
computer, the worst way. USing somewhat different reasoning, Dr. Donald has selected as his
ideotype for wheat a single-culm variety. This is not to say that a tillering plant might not have
advantages in specific localities. Dr. Donald mentions the very obvious advantage of a tillering
rice plant for Japanese conditions where the individual plants are usually set by hand. Scientists
at the International Maize and Wheat Improvement Center in Mexico are interested in the
development of a strongly tillering variety of corn which may have great advantage under some
conditions.
Planting Patterns

7. 
 Dr. deWit has proposes to look under the soil surface to see if there
might be some progressive change in rooting habits. It is not
unreasonable to think that with time in undisturbed soil there are
increased numbers of passages into deeper layers of the soil attributable
to old root channels, insect holes, animal burrows, etc. These channels
are, to a considerable degree, structured so that roots following them
would be led downward, and most such openings would have some
degree of permanence. Plowing presumably interrupts and destroys
such channels and substitutes for them a non-structured and less
permanent porosity
Rooting Patterns

8. 
 It is the procedures we may use to make fullest use of the growing season. This
is not exclusively a temperate zone problem. Even in the tropics there are often
factors that make some part of the year a more desirable growing season than
others.
 Experiment
corn plant early varieties as soon as they can in the spring and spend the
summer hoping they will mature before it snows. In Kentucky if we plant corn
early it will be mature and dead by the last of August. With really early varieties
it will be dead sooner. There is often a month or more of fairly good growing
season left unused. The farther south one goes in the United States the more corn
growing weather is wasted. Our problem is how to translate the unused season
into higher yields. Later varieties grow taller and silk later but there seems to be
little increase in the filling time during which grain is produced.
UTILIZATION OF THE GROWING SEASON

9. 
 Another method for extending the growing season is by using the cooler
part of the year to produce crops that do well at lower temperatures and
follow or precede them with crops that flourish during the warmer part
of the season. Alert farmers in our area are experimenting with various
plans for double cropping to accomplish this and our plant breeders are
developing early maturing small grains to fit into such plans.
Double cropping

10. 
 we are looking for an ideotype that will be short and hence early with
erect leaves and that would have several or very large ears on every
stalk. It would silk ami tassel early and would spend the remaining
growing season filling the kernels pollinated earlier. The time from
silking to maturity would not be affected by temperature. With such
varieties a farmer could buy seed to suit his planting time and the
length of his growing season, and corn yields would increase with the
growing time available. The ideal ideotype for high yields would
germinate quickly in cool soils and grow off rapidly at low and variable
spring temperatures.
Ideotypes

11. 
 Introduction
 Genetic potential of a plant and its interaction with environmental factors decides its
growth and development by influencing or modifying certain internal processes. Plant
physiology studies about these internal processes and their functional aspects.
Reviews of progress made in wheat breeding reveal a number of interesting trends. In the
first place genetic gains in yield seem to have remained relatively steady over the last 30
years, averaging a little under 1% per year in favorable environments .
 In addition, while yield progress is strongly associated with improved partitioning of
assimilates to grain, little progress appears to have been made in improving biomass.
 The integration of rapid physiological screening tools as standard breeding procedure into
breeding programs is addressed as a means of improving the efficiency of breeding and
hence the probability of identifying new combinations of genes which interact favorably
in different genetic backgrounds.
Physiological approaches

12. 
 Radiation use efficiency (RUE) and light interception characteristics have
remained unaffected . Nonetheless, recent examination of yield progress in
irrigated spring wheat showed that biomass has been increased approximately
10% in the latest CIMMYT cultivars
Canopy photosynthesis
 leaf canopies are believed to increase crop assimilation rates, especially in high
radiation environments, and several lines of evidence have supported this
idea.
 Another way of improving canopy photosynthesis may be optimizing the
composition of the photosynthetic apparatus and N distribution throughout
the canopy, so that leaf photosynthesis is equally efficient at different light
intensities.
Radiation use efficiency

13. 
 There are a number of additional physiological traits that have
implications on yield potential and are related to increasing assimilate
(i.e. source) availability. One is the ability to reach full ground cover as
early as possible after emergence to maximize the interception of
radiation
 Another is remobilization of soluble carbohydrates (stem reserves)
during grain filling.
 A third is the ability to maintain green leaf area duration “stay green”
throughout grain filling.
Stem reserves and green leaf area
duration

14. 
 When water evaporates from the surface of a leaf it becomes cooler, and
the rate of evaporative cooling is affected directly by stomatal
conductance, which itself is affected by feedback mechanisms of other
processes such as photosynthetic metabolism and vascular transport.
Canopy temperature depression, therefore, is a good indicator of a
genotype’s physiological fitness, since a high value will be indicative of
good expression for all of those traits under a given set of environment
conditions.
Canopy temperature depression

15. 
 By combining information on the physiological basis of yield limitation with
new physiological selection tools, the probability of accelerating the rate of
genetic progress through plant breeding should be significantly increased.
 Parents can be selected for improved physiological and anatomical traits and
 crossed to high yielding ergonomically elite materials.
 Good performance in a genotype requires complementarily among a number
of different traits so that better performance can be expressed.
 By promoting a large numbers of progeny in the breeding process there is a
chance of identifying phenotypes where favorable interactions among genes
permit the expression of higher yield.
An integrated approach to plant
breeding

16. 
Introduction
In most crop breeding programs, the rate of yield increment is insufficient to
cope with the increased food demand caused by a rapidly expanding global
population. In plant breeding, the development of improved crop varieties is
limited by the very long crop duration. Given the many phases of crossing,
selection, and testing involved in the production of new plant varieties, it can
take one or two decades to create a new cultivar. One possible way of
alleviating food scarcity problems and increasing food security is to develop
improved plant varieties rapidly. Traditional farming methods practiced since
quite some time have decreased the genetic variability of crops. To improve
agronomic traits associated with yield, quality, and resistance to biotic and
abiotic stresses in crop plants, several conventional and molecular approaches
have been used, including genetic selection, mutagenic breeding
Molecular approaches

17. 
 Plants are a rich source of secondary metabolites that have medicinal and aromatic properties. According to some estimates,
at least *100,000 such secondary metabolites are now known to occur in 50,000 plant species and *4,000 new secondary
metabolites are being discovered every year from a variety of plant species For thousands of years, these natural plant
products have been utilized for human healthcare in the form of drugs, antioxidants, flavors, fragrances, dyes, insecticides
and pheromones. However, in recent years, a resurgence of the use of herbal drugs has once again been witnessed, firstly
because the synthetic drugs have been found to be hazardous in many cases, and secondly because there is growing
awareness that the plant-derived medicines have none of the side effects that are so common in the case of synthetic drugs.
The world market for herbal medicines including herbal products and raw materials is actually growing at an annual rate of
5–15%. This is an indication of a possible growing demand for plant-derived drugs in coming years. Despite this, although
the area under cultivation of medicinal crops has been slowly increasing due to increasing demand for herbal drugs. , the
use of medicinal plant species for human healthcare cannot so far take off in any substantial way for the following possible
reasons associated with medicinal crop/plants:
(1) low concentration of desired molecules in specific plant tissues;
(2) medicinal crops being low priority crops;
(3) technical difficulty in cultivation of these crops;
(4) over-harvesting of naturally occurring herbal plants;
(5) destructive collection techniques; and
(6) conversion of habitats of medicinal plants to crop-based agriculture.
 In the recent past, conventional breeding methods (including mutation breeding) have largely been utilized to improve the
yield and quality of secondary metabolites of cultivated species of medicinal value. However, these methods did not give
the desirable level of improvement for several reasons, including sterility, long generation time, perennial nature and
complex biosynthetic pathways involved .
Molecular approaches for the improvement of medicinal and aromatic plants

18. 
 Cloning genes
 Molecular marker technology
a. Random genomic markers
b. Functional markers
 Genetic manipulation using individual structural genes
 Agrobacterium-mediated transformation and RNAi
 Targeting metabolite to specific cellular compartments
 RNA interference (RNAi) technology
 Creation of metabolic sinks for storage of overproducing secondary
metabolites
Molecular approaches

19. 
 During the last several decades, efforts have been made to purify the key enzymes of different metabolic pathways involved in synthesis
of secondary metabolites. A large number of corresponding genes encoding these enzymes have been cloned using three basic
approaches:
 reverse genetic approaches based on purified enzymes,
 similarity-based PCR methods,
 and mutant based techniques.
By applying reverse genetics, knowledge of peptide sequence determined from purified enzymes was used to isolate the corresponding genes
with the help of molecular techniques. This is the most common approach used to isolate most of the genes controlling secondary metabolic
pathways. Because purification of enzymes is sometimes difficult, a general similarity-based, approach was developed, which
helped in isolation of genes encoding enzymes catalyzing pathways common between different organisms. This approach
involves development of gene specific degenerate PCR primers from either conserved motif or any other regions of nucleotide
sequence deduced from protein sequence. These primers have been used to isolate the corresponding full-length cDNA clones. It
is classical and modern genomics approaches, a number of genes encoding enzymes that control the key steps of secondary
metabolic pathways have been cloned from a number of medicinal plant species. The speed of isolating genes involved in
secondary metabolism is still slow due to species specificity, the difficulty in producing large number of mutants and their
analysis, and also to the instability of secondary metabolites caused by environmental factors. However, the implementation of
new functional genomics approach to non-model medicinal plants will boost the speed of discovery and isolation of genes
involved in biosynthetic pathways that lead to production of secondary metabolites.
Cloning genes

21. Plant breeding innovation cycle

22. 
The advantage of conventional plant breeding consists of increasing the
availability of genetic resources for crop improvement through introgression of
the desired traits. However, some plants are at risk of becoming susceptible to
environmental stress and losing genetic diversity traditional cultivation methods
are not sufficient to resolve global food security issues. Combining multiple
phenotypic characters within a single plant variety would successfully increase
yield and has been widely used, however, new breeding techniques are less
expensive and will enable faster production of genetically improved crop
In recent times, improvements in traditional plant breeding have been
introduced, such as wide crosses, introgression of traits from wild relatives by
hybrid breeding, mutagenesis, double haploid technology, and some tissue
culture-based approaches such as embryo and ovule rescue and protoplast fusion
Mutation through Traditional or Conventional Breeding

23. 
 DNA-based molecular markers can also help in improvement of medicinal plant species. These markers can be used for assessing
genetic diversity, authenticating plant material used for drugs and for marker-assisted breeding.
 Random genomic markers Markers commonly used in MAPs mainly include random genomic markers, e.g., RAPD, SSR, SCAR, and
SNP and ribosomal-DNA. These markers have been used in Cymbopogon and Mentha and have helped in characterizing elite varieties
of these MAPs . Efforts have also been made for the development of PCR-based high throughput markers (e.g., SSR, SNP, SCAR) in
some medicinal plants but they need to be developed in all medicinal plants. Recently a very detailed account of genomic markers for
MAPs has been presented by Shasany et al.
 Functional markers : The available nucleotide sequences of genes which have been cloned can also be used to design
primers for functional markers (FMs), to be used as perfect markers for detection of marker–trait associations . These
markers can then be used directly in breeding programs to assess the potential of a genotype at the early seedling stage .
Whole genome sequencing of model plant species such as Oryza sativa (rice) and Arabidopsis thaliana have also been used
for developing FMs. Thus, molecular markers developed from gene sequences of one species can be used for analysis of
marker–trait associations in another species .
Molecular marker technology

24. 
 Transgenic approach for improvement of yield and quality of a secondary metabolite can be used by targeting a rate
limiting step through manipulation of the expression of an individual structural gene. This would increase the flux rate
towards the downstream reactions either by overexpression of genes encoding enzymes or by blocking the competitive
pathways using anti-sense genes or RNAi For example, in the opium poppy, which is the sole source of pharmaceutically
important alkaloid morphine, transgenic plants were produced which had a yield of morphinan alkaloids that was 15%
higher than in the high-yielding control genotypes and 30% higher than in the control non-transgenic segregants.
Targeting metabolite to specific cellular compartments
 Single gene manipulation with the aim of targeting gene expression to specific cellular compartment can be another useful
approach for increasing the concentration of secondary metabolites in transgenic plants. Using this approach, concentration
of terpenoids could be increased several-fold. As is known, biosynthesis of terpenoids occurs via two pathways, one
occurring in plastid (MEP) and the other in cytosol (mevalonate). However, previous attempts made to modify these
pathways through genetic engineering did not involve overexpression of the transgene in a specific compartment.
Consequently, the concentration of the targeted metabolites could not be improved to the commercial level due to the
limited availability of precursors.
Agrobacterium-mediated transformation and RNAi

25. 
 Sometimes, although a plant may have the capacity to synthesize a secondary metabolite, it may lack a proper subcellular
compartment to store it . The genes controlling the formation of such subcellular compartments have been isolated and
characterized in plants . In transgenic cauliflower with an Or gene encoding a DnaJ cystine-rich domain-containing protein,
orange curd with high levels of b-carotene was produced. Cytological studies of transgenics plants revealed that expression
of this gene leads to the formation of large membranous chromoplasts in the cauliflower curd cells . Similarly, transgenic
potato expressing the same gene under the control of a potato granule-bound starch synthase (GBSS) promoter also
increased the total carotenoid levels up to six-fold that in the non-transformed plants. This higher level of carotenoid
accumulation in these transgenic tubers is believed to be due to the formation of carotenoid sequestering structures in
chromoplasts, which provide a metabolic sink to facilitate accumulation of carotenoids. These studies clearly suggest that
manipulation of the formation of deposition sinks offers a new strategy for metabolic engineering of secondary metabolite
content in storage tissues
RNA interference (RNAi) technology
 Using antisense gene for blocking activity of an enzyme is widely accepted, but in case of enzymes encoded by multi genes,
it sometimes fails to block the activity. In recent years, RNAi technology has become an important tool for accelerating the
breeding of aromatic and medicinal plants, where a conventional mutation breeding approach failed .
Creation of metabolic sinks for storage of overproducing secondary metabolites

26. 
https://www.researchgate.net/publication/254988834_Applying_physiol
ogical_strategies_to_improve_yield_potential
https://www.researchgate.net/publication/343889007_Molecular_Appro
ach_for_Crop_Improvement
https://digitalcommons.unl.edu/agronomyfacpub/194
Reference link

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