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Introduction

Maize (Zea mays Linn) is the most widely distributed crop of the world. It adapts easily to a wide range of production environments and is grown in tropical, subtropical and temperate regions of the world. It holds a unique position in world agriculture ranking third after rice and wheat in terms of area as well as production. In India too, it is the third most important cereal crop and is cultivated in 8. 17 m ha (2007-08) area. It contributes nearly 8% to the national food basket and more than Rs 100 billion to agricultural gross domestic products with an annual production of 19. 73 million tons. It is used as a source of human food (24%) animal feed (11%), poultry feed (52%), starch (11%), brewery and seed (1% each). In India it is largely grown in Northern states where it serves as an important staple food for an economically vulnerable population of submountainarean and hilly regions.

Maize (Zea mays L.) occupies an important place in world agriculture due to its high yield potential and greater demand. Because of its divergent character, maize is grown over a wide range of climatic conditions, ranging from near sea-level to several thousand meters above sea-level (2,700 msl). It can also be grown in all types of soils ranging from sandy to heavy clay. Among the factors adversely affecting productivity, incidence of diseases is prominent. In India Maize is prone to a number of biotic stresses like foliar diseases, downy mildews, banded leaf and sheath blight, stalk rots and ear rot caused by fungi and bacteria, incidence of which are variable in time, space, and genotype. Disease may be minimized by the reduction of the pathogen’s inoculum, inhibition of its virulence mechanisms, and promotion of genetic diversity in the crop (Richard et al., 2005). Conventional plant breeding for resistance has an important role to play that can now be facilitated by marker-assisted selection.

Chemical control measures for some of the diseases are helpful in reducing losses, however for stabilizing production it is necessary to build level of genetic resistance. Germplasm improvement programme undertaken in sixties and early seventies by All India Co-ordinated Maize Improvement Project provided an opportunity for combining resistance against important diseases with other desirable agronomic traits. Thus, breeding for resistance had been an important objective of the overall crop improvement programme and it had been a cooperative venture of the plant breeders and plant pathologists. Consequently, it was recognized that there should be an efficient technique for the mass multiplication of inoculums, artificial inoculation technique and scoring/rating of plant disease as a pre-requisite for the successful identification of resistant sources in such improvement programme. With these objectives in to consideration, a six days seminar on the “Techniques of scoring for resistance to diseases of maize in India” was held at Andhra Pradesh Agriculture University, Hyderabad during 15-20 March, 1982 (Payak and Sharma, 1983).

Introduction

The world’s population is expected to grow from 6 billion people in 2000 to 7.5 billion people in 2020. Availability of land for farming is on the decline, and water for agriculture and other uses is increasingly scarce. Together these and other forces will challenge the capacity of the world’s food production system. The world has experienced an unprecedented increase in population during the past century, with a billion people added every decade during the last three decades alone. Dramatic shifts in production and consumption of food have accompanied this population explosion, including a surge in grain production, a spectacular rise in meat production and consumption, and the emergence of an increasingly vital role for international trade (Fig. 1). High-yielding varieties of wheat and rice swept across much of Asia during the 1970s and early 1980s, easing fears of imminent famine. Cereal yields have risen more modestly in recent years, but they have still outstripped gains in other crops such as cassava, potatoes, and beans.

Introduction 
Maize (Zea mays L.) which belongs to the Poaceae family, has its roots in the American continent where it was once grown by ancient cultures like the Indians, Magyars, and Aztecs. Today, maize is one of the most widely cultivated crops globally, with the largest productions in countries such as the US, China, India, and Brazil. As a monocotyledonous and cross-pollinated annual plant, maize is an angiosperm with seeds enclosed in a fruit or shell. The root system of maize is fibrous, reaching up to 60 cm. in soil depth. Maize is a warm-season crop with specific agro climatic requirements for successful cultivation. It thrives in warm temperatures and requires a minimum temperature of around 10°C (50°F) for germination. The ideal temperature range for its growth is between 20°C and 30°C (68°F to 86°F). However, maize is sensitive to frost, and exposure to freezing temperatures can damage or kill the crop. Adequate and well-distributed rainfall is crucial during its growing season, as maize needs about 500 to 1000 mm. (20 to 40 inches) of rainfall to support its development, with higher water requirements during flowering and grain-filling stages. While the crop is moderately droughttolerant, moisture stress at critical growth stages can significantly impact yield. Maize is a sun-loving crop and requires long daylight hours with ample sunshine for efficient photosynthesis and plant growth. The soil should be well-drained, loamy or sandy, rich in organic matter, and have a pH ranging from 5.8 to 7.0 (Greaves et al., 1996). Avoiding waterlogged or compacted soils is crucial, as they can impede root development and nutrient uptake. Maize can be cultivated at varying altitudes, but its suitability is generally limited to elevations below 2,500 meters (8,200 feet) above sea level. The crop typically requires 90 to 120 days from planting to maturity, although some varieties with shorter growing seasons are available for regions with limited frost-free periods. High salinity can result in decreased plant leaves, green weight, fresh weight, shorter shoots, and root length but salt-tolerant varieties have been developed.

Maize (Zea mays L.) has tropical origin and is traditionally grown in monsoon. The crop is grown in diverse geographical and climate conditions around the world and in India maize is grown in kharif (rainy season), rabi (winter season) and spring seasons where more than 70 per cent of the production happen in kharif alone. Of late, the area under rabi maize has increased because of higher productivity and ever increasing demand.

Insect pests of maize

Compared to most cereals, maize faces fewer biotic and abiotic constraints in production. Among biotic stresses, insect pests are major constraints in the production and productivity of maize crop. The earlier literature cites over 160 insect and mite species which attack maize crop (Fletcher, 1914, 1917; Ayyar, 1940; Bhutani, 1961; Pant and Kalode, 1964) but later Mathur (1987) observed over 250 species of pests associated with maize in field and storage conditions. Dick and Guthrie (1988) identified 87 species that directly or indirectly exert severe stress on corn culture in tropical and temperate regions throughout the world. Excluding stored grain insects, Luckman (1978) lists 34 pests or pest groups for which chemical controls are recommended on corn in the United States. There have been more than 130 insect pests reported to cause damage to maize in India but only about a dozen cause economic losses (Sarup et al., 1987).

Plant diseases are of paramount importance to humans because they damage plants and plant products on which humans depends for food, clothing, furniture, the environment and in many cases the housing. The kinds and amounts of losses caused by plant diseases vary with the plant or plant products, the pathogen, the locality, the environment, the control measures practiced and combination of these factors (Agrios, 2005). Disease is one of the major biotic constraints to reduce crop yield and also deteriorate the quality of product that ultimately reduce the market price.

Maize production in India has been dominated by erstwhile Andhra Pradesh and Karnataka which together contribute around 38 per cent of the total maize production of the country. Erstwhile Andhra Pradesh has achieved the highest mean yield of 4441 kg/ha in the country during the last decade (2001-02 to 2010-11) by surpassing Karnataka which had the highest productivity in the country, earlier. The main reason for achieving the highest productivity in the country was due to adoption of improved production technology along with 100% area grown under hybrids. In Telangana, maize is the third most important crop after rice and cotton. It is cultivated in 5.74 lakh hectares, predominantly in Kharif season (4.54 lakh ha), with a productivity of 3.69 t/ha (2015-16).

Trends in maize area, production and productivity in the state (1950 to 2016)

The erstwhile Andhra Pradesh (including Telangana) is the non-traditional maize growing state. But, the climate of the state is very favorable for the crop and hence maize can be grown in any season in the state. However, it is mainly grown as a rainfed crop during monsoon season, concentrated in Telangana. The trends in area, production and productivity of maize in erstwhile Andhra Pradesh have shown a remarkable increase during the past six decades. During 1955-56, the maize acreage in the state was very less (1.89 lakh ha), which has been up by 5.3 times to the present (2014-15) level of 9.95 lakh hectares. The production has also increased dramatically from merely 1.14 lakh tonnes during 1955-56 to 42.36 lakh tones during 2014-15, which is nearly 37 times higher. Similarly, the productivity of maize in the state was merely 601 kg/ha during 1955-56, which has been increased to 4257 kg/ha during 2014-15 (Fig. 1).

Maize is presently the crop with growing importance in the state. Earlier it was primarily grown for human consumption only. In view of rapidly increasing demand of poultry feeds and fodder in Assam presently it has more use in some small industries. It is the raw material for most of the feed industries. Presently the crop has state acreage of 27953 hectare and production of 93179 tonnes with a productivity of 3333 kg/ha (2014-15).

While most other states in India are gradually moving away from their traditional agriculture based economy toward industry or service oriented economy, Assam is still predominantely dependent on the agricultural sector. While the sociopolitical problems afflicting the state since the last few decades are partly to blame for a lack of conducive environment for economic development of the state, particularly in industry or service oriented areas, there are various economic reasons (e.g. fragmented land) responsible for the lagging agricultural sector in the state. Economy of Assam is fundamentally based on agriculture. Over 70% of the state’s population relies on agriculture as farmers, agricultural laborers, or both for their livelihood.

Assam produces both food and cash crops. The principal food crops produced in the state are rice (paddy), maize (corn), pulses, potato, wheat, etc., while the principal cash crops are tea, jute, oilseeds, sugarcane, cotton, and tobacco. Although rice is the most important and staple crop of Assam, its productivity over the years has not increased while other crops have seen a slight rise in both productivity and acreage.

Bihar is an important maize growing state in India after Karnataka, Andhra Pradesh, Telangana, Rajasthan and Maharashtra, where it is cultivated during all season. However, the yield of maize is much higher during Rabi and summer seasons than the Kharif. Due to climate change and other factors, the yield of maize is likely to further decline during the Kharif season. However, the cultivation of maize in Bihar during the Rabi season will be much more profitable as compared to wheat due to rise in temperature. There is need to develop maize varieties which can with stand biotic and abiotic due to changing climate factors.

Decadal trends of maize area, production and stresses yield in the Bihar from 1950–2015.

Chhattisgarh, the 26^th state of the Indian Union came into existence on November 1^st, 2000. The state is geographically situated in the central part of India, between the latitudes of 17° 46' N - 24° 5' N and the longitudes of 80° 15' E - 84° 20' E. Its proximate position with the Tropic of Cancer has a major influence on its climate. The total geographical area is around 137.90 lakh ha of which cultivable land area is 46.77 lakh ha and forest land area is 63.53 lakh ha with more than 2.55 crore population. In Chhattisgarh region about 22% of net cropped area was under irrigation. About 80 percent of the population in the state is engaged in agriculture and 43 percent of the entire arable land is under cultivation. Paddy is the principal crop and the central plains of Chhattisgarh are known as rice bowl of central India. Other major crops are coarse grains, wheat, maize, groundnut, pulses and oilseeds.

Importance of Maize in Chhattisgarh

Earlier maize was mainly cultivated in Surguja and Bastar division of Chhattisgarh but now it is emerging as main cash crop in entire Chhattisgarh state. There had been an increase of 20 per cent in maize crop acreage in Chhattisgarh during the past 10 years. Now the farmers of the area are cultivating maize in lines, applying atrazin weedicide, full dose of chemical fertilizers, etc. They are willing to buy the hybrid seed for cultivation from the market and taking maize as green cob and also utilizing as green fodder. Maize threshers have been purchased by some farmers in the region which is an indicative of large maize production.

For industrial utilization of the maize Chhattisgarh state has “Raja Ram Maize Factory” in Rajnandgaon district. They are producing and supplying Maize starches, liquid glucose, dextrose mono hydrate, dextrin, maltose liquid, malto dextrin, maize oil, maize gluten, maize grit, maize husk etc. But most of the maize production is used as poultry feeds in the state. Traders purchase it directly from the farmers’ fields in the villages. It is also exported to the neighboring states either as grain or green cob. Around 10-15% is retained by the farmers for own consumption and seed purpose.

Maize ranks fourth after rice, wheat and bajara with respect to area and production, and grown on 4.23 lakh ha average with 6.72 lakh tones production and yield 1589 kg/ha in the Gujarat (2014-15). The state has 38.0% lower than national yield. It mainly grown in Panchmahal, Dahod, Mahisagar, Vadodara, Chhota Udepur, Kheda, Sabarkantha, Banaskantha and Aravali districts as rainfed Kharif and irrigated winter/Rabi crop for food, feed and industrial raw materials.

It is staple food and feed of tribal and grown as sole and intercrops with pigeon pea, black gram and soybean in Kharif season. The white and yellow flints to semi-flint maize are preferred to prepare bread and other food preparations

Maize is one of the most important food, feed, fodder and industrial crop in Haryana and is cultivated in all the three seasons (Kharif, Rabi and spring). It was cultivated on 6 thousand hectares in Kharif season with average productivity of 2.83t/ha during 2015-16. The maize is also increasing in spring season which was grown on ~ 7 thousands hectare with productivity of 4.5t/ ha. The specialty corn (baby corn and sweet corn) is also grown in >2 thousand hectare area of Haryana in national capital region. The demand of maize is increasing every year due to growth in poultry industry and expansion of maize based industries. There is a good scope of cultivation of specialty types of corn (baby corn, quality protein maize and sweet corn) in Haryana as it is very near to national capital, Delhi. The cultivation of specialty corn and its value addition by establishing

Maize (Zea mays L.) is one of the most versatile crops having the highest genetic yield potential among cereals and wider adaptability under varied agro-climatic conditions rightly earning it the name of ‘the queen of cereals’. Maize is cultivated in all agricultural areas around the world and is an economically significant crop for all human population. It is grown from 58⁰ L north to 40⁰ L south and extends from the sea level up to an altitude of above 3,800 m; covering regions with rainfall varying from 250 to 10,000 mm (Hallauer and Miranda, 1988). Globally, maize occupies an area of about 184.0 million ha with production of 1065 million tons and productivity of 55.2 q/ha (FAOSTAT, 2014). It is the third most important cereal crop and a major source of energy, protein and other nutrients for human and livestock in the world (Jompuk et al., 2011). India is the second most important maize growing country in Asia, and now ranks as the world’s fifth largest consumer of maize. It is an important cereal crop in India covering an area of 9.42 million ha with a production of 24.35 million tonnes and productivity 25.83 q/ha (Anonymous, 2015). Maize is cultivated in the country throughout the year mostly during rainy or Kharif season (June to September, 80%) followed by winter or Rabi (November to April,18%) and spring (February to May, 2%) for various purposes including grain, fodder, green cobs, sweet corn, baby corn and popcorn.

Agriculture is the predominant sector in the economy of Jammu and Kashmir. Directly and indirectly, it supports about 80 per cent of the population besides contributing nearly 60 per cent of the state revenue. The total geographical area of the state is nearly 22.2 million hectare and population of 12.5 million, which is approximately 1.04% of the national total. The J&K is divided into three agro-climatic zones: Cold arid desert areas of Ladakh, temperate Kashmir Valley and the humid sub-tropical region of Jammu. Each has its own specific geo-climatic condition which determines the cropping pattern and productivity profile.

In Jammu province, a small portion of the land lies in the plains along the borders of Punjab while the rest of the area is hilly, dominates both in maize and wheat production. About 67 per cent of the area is under maize and wheat production with the production of 21.25q/ha maize and 15.36 q/ha wheat. This region contributes 79.56 per cent and 95.69 per cent of total production of these two cereals respectively. Even though the yield is not high, the region makes appreciable contribution to the cereals production.

The second agro-climatic zone Kashmir is also known as ‘cultivator’s paradise’. The region practically depends on irrigation, which is easily available. A large area of level land has alluvial soil. Extensive elevated plateaus of the alluvial or lacustrine material (locally called Karewas) also exist in the Kashmir valley. These Karewas are productive only in the face of sufficient rainfall or adequate irrigation facilities. Rice is the chief crop of this zone, followed by maize, oat, barley and wheat.

Ladakh zone is endowed with bare rocky mountains and bare gravel slopes. Villages are located near pockets of land with level ground and irrigation facilities, where cultivation is viable. In this region, barley is the major cereal crop followed by summer wheat. Millets and wheat rank second in importance and are grown in the warmer belt of the region.

Maize or corn (Zea mays L.) is second most important crop after rice in Jharkhand. Though considered as a Kharif season crop, it can be successfully grown in other two crop seasons viz., Rabi and zaid also as the climatic condition in Jharkhand is conducive for growth of the plants. Rabi maize has comparative advantage over Kharif maize due to low incidence of diseases and insect pests slow growth of weeds and crop does not have to suffer on account of heavy rainfall hence, higher yield potentiality could be realized from Rabi maize. In Jharkhand, the Kharif crops including the maize are grown as rainfed as the 80 to 85% of the annual rainfall takes place during June to September. The share of maize under irrigated condition is restricted to only 15 to 18% of the total cropped area. Maize is not only an important source of nutrient to the human beings but also constitutes a basic component of animal and poultry feed. Here, farmers grow maize mainly for green cobs as cash crop whereas the grains are to be used for human consumption as well as for animals and poultry feed. The cultivation of the specialty corns like baby corn, sweet corn and popcorn is still in its infancy in Jharkhand and hence, large scale cultivation of specialty corn in the state will take some more time. Establishment of food processing unit in the state is at the nascent stage. However, the Government of India is implementing a Mega Food Park in Getalsud Industrial Area of Ranchi district in Jharkhand. The establishment of this mega food park is expected to give a significant boost to the food processing sector in Jharkhand.

Karnataka is India’s eighth largest state in geographical area covering 1.92 lakh sq km and accounting for 6.3% of the geographical area of the country. As per the population Census 2011, agriculture supports 13.74 million workers, of which 23.61 per cent are cultivators and 25.67% agricultural workers. A total of 123,100 km² of land is cultivated in Karnataka constituting 64.6% of the total geographical area of the state (Table 1). Of the total cultivated area in the state, about 33.0% is covered by cereals, 42% by pulses and 19% by oilseeds and 6.0% by commercial crops (Savitha and Kunnal, 2015). Agriculture employs more than 60% of Karnataka’s workforce. The large portion of agricultural land in the state is exposed to the vagaries of monsoon with severe agro-climatic and resource constraints.

The state of Madhya Pradesh is one of the high profile maize growing state of the country cultivating maize in about 11.32 lakh hectare area which is ~12% of the total maize area of the country having 90-95% of total maize area having rainfed. Madhya Pradesh is situated in heart of India between 17°-26° N latitudes and 74°-84° E Longitude. The rainfall in maize growing belt varies from 800 to 1600 mm. Due to erratic and uneven rainfall in the state, the production and productivity of maize fluctuates every year. Maize cultivation in the area is associated with resource poor tribal farmers. As the demand for maize is growing globally due to its multiple uses for food, feed and industrial uses, we need to produce more from same or even less resources, which can be achieved through targeting technologies in potential regions.

Besides, monsoon crop due to mild winter conditions the climate allows the cultivation of maize during winter successfully under assured irrigation conditions. At present about 50 thousand ha area is under Rabi cultivation with high productivity levels as compared to monsoon crop. However, the major area increase was achieved during past few years mainly due to adoption of hybrids and shift in acreage under non-traditional areas, replacing soybean crop on farmers field. Uncertain climatic conditions and more disease and pest problem lead farmers to adopt maize in place of soybean.

The trends in area production and productivity of maize in Madhya Pradesh has shown a remarkable increase during four decades. During 1966-67 the maize acreage in the state was very less (5.59 lakh ha) that has grown up by 11.32 lakh ha in 2014-15. Moreover, the productivity also increased dramatically from mere 811 kg/ha during 1966-67 to 1513kg/ha in 2014-15.

Maharashtra is the third largest state in terms of area in the country located in the north-centre of peninsular India. It links the southern part of the northern plains to the southern peninsula. Maharashtra occupies the western and central part of the country with total 3.08 lakh sq. km geographical area and has a long coastline stretching nearly 720 kilometers along the ARabian Sea. The prominent physical trait of the state is its Plateau character, which has up to 1350 meters high altitude. Physiographically this state may be divided into three natural divisions-the coastal strip (the Konkan), the Sahyadri or the Western Ghats and the Plateau. The Sahyadri mountain ranges provide a physical backbone to the state on the west, while the Satpuda hills along the north and Bhamragad-Chiroli-Gaikhuri ranges on the east serve as its natural borders. It has a geographical area of 307713 sq. km and is bounded by north latitude 15°40’ and 22°00’ and east longitudes 72°30’ and 80°30’.

NBSS & LUP has divided the state into 356 soil mapping units and published a map of the soils of Maharashtra. It has broadly categorized as soils of Konkan coast, soils of Western Ghats, soils of upper Maharashtra, soils of lower Maharashtra. The soil status of Maharashtra is residual, derived from the underlying basalts. In the semi-dry Plateau, the regur (black-cotton soil) is clayey, rich in iron and moisture-retentive, though poor in nitrogen and organic matter. The rainy Konkan and the Sahyadri Range, the same basalts give rise to the brick-red laterites, which are productive under a forest cover, but readily stripped into a sterile varkas when devoid of vegetative cover. The soil in the Deccan Plateau is made up of black basalt soil. This type of soil is rich in humus. The soil is commonly known as the black cotton soil because it is best suited for the cultivation of cotton. The volcanic action which had taken place in the Deccan region has given rise to the soil texture and composition. These igneous rocks break down into the black soil which is very fertile. The Wardha-Waliganga river valley has old crystalline rocks and saline soils which make the soil infertile. This type of soil has a natural resistance to wind and water erosion because it is rich in iron and granular in structure. A very important advantage of this type of soil is that it can retain moisture. This makes the soil very reactive to irrigation.

Maize is the only cereal crop which is being used as human food, animal feed and as a source of large number of industrial products. In Odisha traditionally maize is a Kharif season crop and second most important crop next to paddy during Kharif season in terms of both area and production. The Rabi maize is cultivated under irrigated condition, and accounts only 7% of total area and production of the State. While only 24% of the Kharif maize area have irrigation facilities. Irrespective of the season, it is that is the fourth most important food grain crop with respect to area in the state which is next to rice, mungbean and urdbean. Even though maize is grown as a sole crop in the state but, some farmers are also adopting maize based inter-cropping and the major recommended/adopted inter-crops are arhar, cowpea, yam, runner bean, greengram and blackgram. The comparative analysis of compound annual growth rate (CAGR) of area, production and yield of the major crops is the state was done for the years 2004-05 to 2013-14. The CAGR study of major crops revealed that no other major crop including rice has the impressive growth rate a like maize in the state (Fig. 1).

Maize is one of the most important cereal crops of the world. Being a C₄ plant, it is physiologically more efficient than rice, wheat and other important cereal crops which belong to C₃ category. In Punjab, traditionally, maize is grown during Kharif season but from last few years the area under spring maize is increasing because its cultivation is highly profitable and commercially viable after harvesting of potato crop. No doubt, Punjab has been the leading state in contributing to the national food security but simultaneously paddy-wheat rotation resulted in depletion of underground water, deterioration in soil health and environmental pollution. These problems need to be addressed for the sustainability of these natural resources and at the same time meeting the food grain production for the ever-increasing human population. Under such circumstances, maize crop is a viable alternative to replace some area occupied by rice and can help in breaking rice–wheat dominant cropping pattern in the state. Promising maize hybrids possessing high grain yield potential and offering comparable economic returns to the farmers are available with Punjab Agricultural University as well as with the private sector.

In Punjab, maize is commonly used in the form of chapatis, boiled or roasted green cob, breakfast food like cornflakes, popped grains etc. Maize chapatis are used as a delicacy with saag. The high carotene content of yellow grained maize is considered very useful in imparting yellow colour to egg yolk. Therefore, a substantial quantity of maize grain is utilized as an important ingredient of animal/ poultry feed industry. The use of maize grains for such purposes is going to increase as poultry and dairy industries are expanding. Maize plant is extensively used as green as well as dry fodder. The digestibility of maize fodder is better than sorghum, bajra and other non- legume forage crops. Maize plant does not have any anti quality factor hence can be fed to cattle at any stage. Maize can be utilized as an industrial raw material for number of industries viz., starch, ethanol, rubber, paper, cosmetics and pharmaceuticals etc. Quality Protein Maize (QPM) can be promoted for nutritional security of poor masses whereas pop corn, baby corn and sweet corn can help in increasing the farm income due to high market value. In Punjab, major industries which are utilizing maize are The Sukhjit Starch & Chemical Limited, Kapurthala, and M/s Field Fresh Food Pvt. Ltd, Ladhowal, Ludhiana.