Around the globe, a 932.2 million hectare area is affected with salinity and sodicity stresses (Metternicht and Zinck, 2003), out of which, an area of nearly 6.73 million hectare is affected by these stresses in India. Further, the arid and semi-arid areas in different states are associated with underground saline water, which have to be used for irrigation, due to the unavailability or diversion of good quality water to other than agricultural purposes. The use of such water is further rendering the soils unfit for crop cultivation. Rapeseed mustard is the third most important source of vegetable oil in the world and is grown in more than 50 countries across the globe. China, Canada, India, Germany, France, UK, Australia, Poland and USA are the major cultivators of its different species of Brassica. During 2012–2013, the estimated area, production and yield of rapeseed mustard in the world was 30.74 mha, 60.43 mt and 1.95 tonnes/ha, respectively. Globally, India accounts for 21.7% area and 10.7% production (USDA 2013). Brassica rapa, B. napus and B. juncea are grown predominantly for oil and seed meal. India is the second largest country in rapeseed mustard production and more than 85% of its area under rapeseed mustard is occupied by Indian mustard B. juncea (L.) alone, because, compared to the more widely grown brassica species B. napus and B. rapa, B. juncea is more tolerant to heat and drought stress, has high yield potential and wide adaptability. The species does not shatter as readily as B. napus and so it can be straight cut or swathed and combined.

Salinity affects the growth and development of brassica juncea in various ways. The most common adverse effects of salinity on Brassica are the reduction in plant height, size and yield as well as deterioration of the product quality (Zamani et al., 2011). Soil salinity markedly affected the lipid components of mustard seeds (Brassica juncea). With increasing salt levels, total and neutral lipids declined considerably, while phospholipids and glycolipids increased. The fatty acid profiles of total, neutral and polar lipid fractions were affected substantially. Erucic acid in total and neutral lipids decreased, while it was absent in the polar lipid fraction. In total and neutral lipids, oleic and linoleic acids increased. The amounts of linoleic and linolenic acids in the polar lipid fraction increased with rising salinity. Plant dry weight drastically declined at higher salinity levels (ECe 8 and 12) whereas the maximum weight was observed at ECe 4 (Parti et al., 2003). Brassica cultivars showed comparatively lower percentages of oil content in seeds under saline sodic soil conditions (Ece = 13.02 dS m and SAR = 12.70). It might be due to an excessive absorption of toxic ions disturbing metabolic processes. Furthermore, nutritional imbalance as a result of depressed uptake of nutrients, shoot transport, chlorophyll breakdown and impaired distribution of mineral ions retarded the development of seeds and early maturity of plants under high salinity treatments might be responsible for the reduced oil content (Ali et al., 2013, Mahmood et al., 2007).

In addition to a decrease in the mobilization of photosynthates towards developing siliqua, salinity also adversely affects the deposition of lipids. Fatty acid composition has revealed that erucic acid decreased marginally and this reduction was accompanied by an increase in linolenic acid and eicosenoic acid (Sharma and Manchanda, 1997, Sureena et al., 1999).

The irrigation of mustard with saline water (3500 ppm) raised the values of erucic acid followed by oleic acid to 40.98 and 20.49% respectively, as compared to 30.82 and 15.59% in the controlled treatment (Abd El-Wahab, 2013).

Improved genotypes of mustard with tolerance to high salt along with consumer acceptance and good oil quality are required for obtaining optimum yield and expansion of the cultivated area under such stress situation. These concerns prompted an intensive breeding program to develop high yielding cultivars with salinity tolerance at the Central Soil Salinity Research Institute (CSSRI).]

CSSRI has developed three high yielding salt tolerant varieties of Indian mustard (Brassica juncea) i.e. CS 52, CS 54 and CS 56. Further, information on the effect of salinity on the oil quality, nutritional and anti-nutritional make-up of mustard oil would be quite useful for the breeders in the quality improvement programme to make this crop globally competitive.

Indian mustard varieties exhibit quite high contents of erucic acid in oil (more than 40%) (Chauhan et al., 2007). A high amount of erucic acid in edible oils has been reported to impair myocardial conductance, causes lipidosis in children and increases blood cholesterol (Ackman et al., 1977). Because of the adverse effects of high erucic acid in the oil of Indian mustard varieties, the varietal improvement programme in India aims at reducing the erucic acid level up to internationally accepted norms (less than 2%) which necessitates the screening of a large number of samples with limited seed availability especially in potential germ plasm.

In addition, the high fiber content (12–13%) in the seed meal reflects lower values of metabolizable energy and may negatively influence protein digestibility and the bioavailability of minerals such as magnesium and zinc (Simbaya et al., 1995; Ahuja and Bajaj, 1999; Chauhan et al., 2002).

In order to utilize or develop genotypes with high contents of oil and protein and low contents of fiber and erucic acid, a rapid and reliable screening of existing genotypes is required.

Plant breeding programs usually involve extensive evaluations of the quality components of interest. Thus, large numbers of screenings by the standard analytical methods of seed lines are usually performed in order to detect target genotypes. Currently, chemical analytical methods are generally used to estimate oil, erucic acid, protein and crude fiber contents. Although the standard analytical techniques usually offer a high level of accuracy and precision, these methods are expensive, time consuming, and require the destruction of seed samples which could be a handicap in the case of valuable and scarce materials.

In recent decades, the development of low cost, non-destructive, high output equipments featuring improved electronic and optical components, the advent of computers capable of effectively processing information contained in spectra and the development of powerful chemo-metric applications has facilitated the expansion of spectroscopic techniques in an increasing number of fields, allowing for an efficient management of spectral and chemical data. The screenings of materials and applications of such selection techniques would increase breeding efficiency.

Newer technological advances have brought about a rapid, lower cost analytical technique called Fourier Transform Near Infrared Reflectance (FT-NIR) spectroscopy. The use of FT-NIR spectroscopy has already been reported for the non-destructive screening of oil, fatty acids, protein, amino acid, and individual and total glucosinolate contents of rapeseed mustard seeds (Petisco et al., 2010; Chen et al., 2011) in large breeding populations.

Moreover, FT-NIR spectroscopy is a fast, accurate, and non-destructive technique which requires minimal or no sample preparation and can be used as a replacement of conventional time-consuming chemical methods. It is also interesting to note that NIRS does not require the use of solvents, thus is environmentally friendly, which is currently a major concern. To date, no attempt has been made to assess the impact of salinity on oil quality parameters for mustard on intact seeds by FT-NIR spectroscopy.

Keeping in view the potential advantages of NIRS over chemical methods, the present study was undertaken to develop calibration models and to assess their application in estimating the effects of salinity on oil quality parameters of Indian mustard genotypes and to explore its applicability in identifying variability for these traits.

The experiment was conducted at the Research Farm Karnal (Non-saline field) and out station experimental farm, Nain (Saline field) of the Central Soil Salinity Research Institute (CSSRI), during Rabi 2011–12 and 2012–13. The experimental materials for the present investigation consisted of 97 salt tolerant Advance Breeding germ plasm lines of the Indian mustard developed by CSSRI.

All the materials were evaluated in a randomized block design with three replicates in two environments viz. normal (pH = 7.6 and ECe 3.9 dSm^-1) and saline (pH = 8.3 and ECe = 10.7 dSm^-1) and irrigated with water having pH = 7.7 and EC_iw 3.8 dSm^-1 at both Research farms; Karnal and Nain. The salinity of the saline soil is above the threshold limit for mustard under field condition ECe 8.2 dSm^-1 reported by Minhas and Gupta (1992). The seed analysis for oil, protein, erucic acid and crude fiber content was conducted using a pre-standardized Fourier Transform Near Infrared Reflectance Spectrometer (FT-NIR, Perkin Elmer, Massachusetts, USA). Further, the best performing advanced breeding lines out of 97 along with national check (CS 54) for salinity evaluation trials were evaluated under controlled condition in pots in the laboratory.

The plants were grown in 20 kg capacity plastic pots in sand culture and irrigated with five levels of salinity (EC_iw 0, 9, 12, 15 and 18 dSm^-1) throughout the experiment during 2011–12 and 2012–13. Saline irrigation water was prepared by adding NaCl, CaCl₂ and Na₂SO₄ and maintaining Na: Ca and Cl: SO₄ ratio as 4:1 respectively. The pots were arranged in a factorial experiment based on a completely randomized block design (CRBD) with 4 replicates. The seeds were surface-sterilized for 5 minutes in 10% sodium hypochloride solution and then rinsed with distilled water. Five seeds of each genotype were sown at 1 cm depth in each plastic pot (20 Kg capacity) filled with thoroughly washed river sand. The bottom of each pot was delved for drainage of extra water. The pots were irrigated with a nutrient solution (Hoagland’s solution) and maintained at full strength field capacity till germination. After germination, the number of plants was reduced to two seedlings per pot. Salinity stress was imposed at the four leaf stage and different levels of salinity were achieved by step-wise addition of saline solution to each pot so as to avoid shock. Thereafter, the salinity levels were maintained throughout the experiment by flushing the salt daily from the pots. At harvest seed yield was recorded. The whole seeds obtained were subjected to the above mentioned analysis using FT-NIR.

The present investigation revealed that FT-NIR is an accurate and powerful technique that could be applied successfully for rapid mass screening of the potential germ plasm for selecting high oil and protein, low crude fiber and erucic acid contents. The threshold limit of salinity for mustard, up to which little or no reduction in yield occur, is 8.2 dSm^-1 under soil (ECe) and 12 dSm^-1 for irrigation water (EC_iw), and for every increase of 1 dSm^-1 in EC above the salinity threshold results in a reduction in the oil, protein and crude fiber of about 1–3%, 4–6% and 5–8%, respectively, whereas erucic acid increased by 5–9%.