Quality Characteristics of Indian Wheat

After rice, wheat is the most important cereal in India. It is grown in cooler regions of India during the mild winter months of November to mid-April. Nearly 26 million hectares (mio ha) are sown with wheat. Of this, 24.5 mio ha are sown with spring bread wheat or Triticum aestivum, nearly 1.5 mio ha go under durum (T. durum); Khapli or T. dicoccum covers less than 50,000 ha, and a few fields of T. monococcum have been reported from Rajasthan. India's annual wheat production has been around 72 mio tons for the last few years, with minor variations between years. This puts India in second position among the wheat producing countries, with approx. 12 % of the world's wheat production. But India is also the second largest wheat consumer after China, with a quickly growing demand. The diverse growing environments are used to produce wheat grain with different quality attributes, so India is able to meet both domestic and international consumer needs.

1. India's Wheat Growing Zones
Wheat is the most important winter cereal grown during the non-monsoon months, and it is less vulnerable to yield fluctuation than other crops. On the contrary: production of the monsoon-season rice crop is dependent on good rainfall distribution. In order to have a reliable and robust food security system it is essential to have an adequate quantity of wheat.
Fig. 28: Wheat growing zones. (The boundaries of India as shown in this map are neither accurate nor authentic.)
The wheat-growing parts of India differ considerably in respect of soil type, temperature and moisture regime and are divided into six mega environments (Fig. 28): Northern Hill Zone (NHZ), North West Plain Zone (NWPZ), North East Plain Zone (NEPZ), Central Zone (CZ), Peninsular Zone (PZ) and Southern Hill Zone (SHZ). The NHZ has approximately 1.2 mio ha under wheat, which is grown at various elevations; on slopes it is un-irrigated, whereas irrigation is feasible where rivers flow.

The NWPZ is the fertile, canal and tube irrigated (> 90%) tract of the Gangetic plain, with alluvial soil and a very low gradient. Here, wheat occupies more than 9.0 mio ha. For several days the minimum temperature remains around 5 °C. In NWPZ wheat matures in 140 days, tillers well with more grains per spike and therefore has a very high yield. The limitations are the occurrence of karnal bunt (Tellesia indica) disease and grain shriveling due to a sudden increase in the maximum temperatures around grain filling time.

The NEPZ has a network of rivers and drains, with high humidity, high soil pH and irregular topography with unreliable irrigation services. The wheat season is foggy for several days, and dew condensation on the leaves promotes severe leaf blight (Dreschlera spp.) and brown rust (Puccinia triticiana). Wheat matures here in 125 days and may be affected by pre-harvest summer showers. The more than 9.0 mio ha under wheat in this zone falls into several cropping sequences resulting from the irregular topology, the low-lying area near rivers causes staggered wheat sowing.
Fig. 29: "Tropicalized wheat". IARI variety HW 3070 is grown in Tamil Nadu, close to the equator. Note coconut and wheat growing in the same ecosystem.
The CZ and PZ are predominantly highland areas with deep black soil, and in these tracts wheat is grown over 5.0 mio ha and 1.0 mio ha, respectively. Here wheat is cultivated under retreating soil moisture conditions and at best, in some areas, farmers are able to provide two irrigations. Wheat crops mature in 100 to 110 days and are continuously exposed to high temperatures (Fig. 29). As a consequence there is poor tillering, and the number of grains per spike is less, so per hectare productivity is only around two tons. The low yields are compensated for by the high quality of the grain. In the SHZ only a few hundred hectares are under wheat, and these hills are the main source of inoculum against stem (P. graminis tritici) and leaf rust (P. triticiana) for PZ and CZ. Hence, the development of rust-resistant varieties is an important strategy for reducing crop loss in PZ and CZ.

2. Wheat Varieties
In the last forty years more than 200 wheat varieties have been released for cultivation in the six mega wheat growing environments. Most of the wheat varieties released for cultivation are for irrigated, high-fertility, timelysown conditions or for the late-sown situation. Rain fed crop growth conditions may account for 12% of the net area sown to wheat, and all Khapli is grown as a rain fed crop. The seed replacement ratio in wheat is very poor and mostly it is farmers' retained seed that is exchanged horizontally between farmers.

Although breeders produce seed for more than sixty wheat varieties each year, a maximum of fifteen varieties accounts for 80% of the crop, and of these one or two cultivars cover 30% of the area.

Grain Quality
The physical aspects of grain quality include external features, foreign matter presence, plant debris damage due to saprophytes, grain diseases, stored grain pest damage and seed damage due to post-harvest operations.

Physical Purity
The manual harvesting and threshing of wheat practised earlier used to continue for two months after the harvest. But the situation changed dramatically in the 1970 s, when farmers mechanized their operations with tractor power. Following this, the local manufacture of threshing machines started. Threshing and winnowing operations are now completed quickly by mechanical means. In NWPZ nearly 60% of the wheat area is harvested by combines on a custom hiring basis, whereas in the NEPZ and the PZ there is less use of combines. The combine contractor roves over the wheat growing continuum of the NWPZ and facilitates the harvesting process. The combine is generally not well kept, and is only cleaned from time to time. It also carries a substantial amount of seed from one field to another, thus promoting grain admixture. In the combine-harvested fields there is a large percentage of broken grain because of poor maintenance of the machine or over-drying of the standing crop. Plant debris, weed seed and foreign matter are also abundant in combine-harvested fields, and if the farmer does not fine-clean his harvest it is difficult to market the produce.
Fig. 30: Physical purity of freshly harvested wheat samples from different states of India (data from AICWIP report, 2004).
There are more shrunken and broken kernels in the freshly harvested grain lots of Punjab, Haryana and the Plains of Uttaranchal, and to some extent in Uttar Pradesh where combine harvesting is common practice. In states like Uttar Pradesh, Haryana and the Plains of Uttaranchal many varieties are grown, and the admixture of grains from different classes happens frequently. Foreign matter content is very high in the grain harvest from Madhya Pradesh, and the percentage of damaged kernels is distinctly high in the freshly harvested grain samples from Punjab. In general the samples from NWPZ, which is the largest grain surplus producing area, have low physical purity and fall into grade II or III. Fig. 30 summarizes the physical purity of wheat samples from different states in 2004.

Other Physical Features Relevant to Milling
Physical characteristics such as hectoliter weight, thousand grain weight, grain hardness and texture are important for the grain trade. The wheat grain samples from Punjab have a hectolitre weight (HLW) of approximately 78 (kg/100 L), a thousand grain weight of about 37 g and a sedimentation value of < 40. The low temperature during the initial plant growth stages promotes the number of grains per spikelet. The accelerated ripening due to sudden terminal heat often results in small grain of uneven seed size. There are varietal differences in seed size and thousand grain weight, and the large-seeded genotypes rarely produce more than 3 or 4 grains per spikelet. The wheat kernel from NEPZ is generally large with more than 10% seed moisture, and has a sedimentation value above 40. The grains from PZ and CZ are hard and lustrous, with > 80 HLW and yield around 70% flour recovery.

Based on physical parameters and purity, Indian wheat has been grouped into five different grades in accordance with the international grading system. The durum wheat grain is generally large and hard with a higher hectoliter value. The CZ grain samples of bread wheat often have > 10% durum grain as an admixture. Millers do not like such material, since it impairs the quality of the flour. Most of the fresh grain arrivals from the farm need a first round of cleaning before they are graded, dried and sent to the silo for storage. This cleaning causes a 2.3 to 24.0% loss, depending on the grain grade (Gupta et al., 2002) and thus reduces the profit margin of the trader and the cultivator.

Micronutrient Status of the Grain
The micronutrient level of the grain is important. If it is low, it becomes necessary to supplement the flour with zinc, iron, etc. Such fortification raises the cost of the product, and to some extent this issue of micronutrient enrichment of the grain can be addressed through plant breeding. The micronutrient content of Indian wheat varies considerably. For example, C 306, C 591, K 68, UP 262 and WH 712 have higher Zn, Fe and Cu levels than the recently most popular varieties such as HD 2329 and PBW 343 (Tab. 43). The micronutrient content in the first group of varieties and their excellent chapatti-making quality make them ideal grain types, and so they generally fetch a premium price in the market. The well-funded global programme "Harvest Plus" of the CGIAR (Consultative Group on International Agricultural Research) addresses the issue of micronutrient enhancement. Many national programmes are also targeted towards accumulating the micronutrient-enriching genes in high yielding wheat. The information available indicates that it is possible to combine good micronutrient levels with high yield as in the case of WH 712 and with a good gluten score, sedimentation value and chapatti-making attributes (chapatti is flat, non-fermented Indian bread).
Tab. 43: Micronutrient, sedimentation-value and HMW data for Indian wheat

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