Screening of Soybean (Glycine Max (L.) Merrill) Genotypes for Resistance to Rust, Yellow Mosaic and Pod Shattering

Soybean (Glycine max (L.) Merrill) is known as ‘Golden bean’ and miracle crop of 20th century. Soybean is a native of North China, Asia belongs to family fabaceae. It is a versa‐ tile and fascinating crop with innumerable possibilities of not only improving agriculture but also supporting industries. Soybean besides having high yielding potential (40-45 q/ha) also provides cholesterol free oil (20%) and high quality protein (40%). It is a rich source of lysine (6.4%) in addition to other essential amino acids, vitamins and minerals. Its oil is also used as a raw material in manufacturing antibiotics, paints, varnishes, adhe‐ sives and lubricants etc.


Introduction
Soybean (Glycine max (L.) Merrill) is known as 'Golden bean' and miracle crop of 20 th century.Soybean is a native of North China, Asia belongs to family fabaceae.It is a versatile and fascinating crop with innumerable possibilities of not only improving agriculture but also supporting industries.Soybean besides having high yielding potential (40-45 q/ha) also provides cholesterol free oil (20%) and high quality protein (40%).It is a rich source of lysine (6.4%) in addition to other essential amino acids, vitamins and minerals.Its oil is also used as a raw material in manufacturing antibiotics, paints, varnishes, adhesives and lubricants etc.
Like other economically important crops soybean is also suffering from many diseases viz, rust (Phakopsora pachyrhizi Syd.) and yellow mosaic (Mungbean Yellow Mosaic Virus) are the major disease under Indian conditions, which causes considerable reduction in yield up to 80 per cent under severe conditions [3].Further, another major problem in soybean is pods shattering which also reduces yield and in some varieties 100 per cent yield losses have been observed.The extent of yield loss due to pod shattering may range from negligible to significance levels depending upon the time of harvesting, environmental condition and genetic endowment of the variety [11].Hence screening for soybean genotypes for identifying resistance to above major problems with high yielding potential will help to increase the production to a greater extent.

Materials and methods
The material consisted of 84 genotypes of soybean originated from different places of India and abroad.The experiment was laid in augmented design at the Research Farm of Kisan (PG) College, Simbhaoli, Ghaziabad, during kharif, season of 2008.In each replication the genotypes were grown in 2 m long rows with spacing of 40cm × 10cm for row to row and plant to plant, respectively.Within a row, seeds were hand dibbled 10 cm apart.Standard package of practices was followed to raise the crop.Ten competitive plants were randomly selected from each treatment in each replication and data were recorded on 3 qualitative characters namely, pod shattering resistance, rust resistance and yellow mosaic disease resistance.

Screening for pod shattering resistance
The pod shattering resistance was recorded at physiological maturity of the pod.The screening was done under laboratory condition by following the methodology adopted by IITA [4].The results were recorded as percentage of pod shattering.IITA method of calculating pod shattering under lab conditions: A sample of 25 pods were collected and kept in oven at 40°C for 7 days.
On the 7th day the number of shattered pods were counted and expressed in percentage as below,

Total number of pods
The genotypes were classified into different categories based on their reaction to pod shattering.The scoring rate was followed according to method adopted by IITA.

Sl.No
Category Resistant reaction

Screening for rust resistance
Growing resistant varieties is the most economical and safe method of controlling the rust of soybean, which is a devastating disease resulting in heavy yield loss.In order to identify the resistant cultivars 84 genotypes of soybean were screened for rust resistance during kharif 2008 under natural epiphytotic conditions at Dharwad.The rust incidence was recorded at physiological maturity of the genotypes and the results are presented in Table 3.Reactions of 84 genotypes to rust revealed that, none of the genotypes showed immune reaction to rust.Two genotypes viz., EC 241778 and EC 241780 showed resistant reaction (1 grade), which were considered as resistant and the remaining 82 genotypes as highly susceptible (9 grade).

Screening for pod shattering resistance
Pod shattering is one of the major constraints in soybean, which reduces the yield potential considerably.So management of pod shattering is of great importance for achieving higher productivity.Hence, the identification of resistant sources for pod shattering is one of the most important aspect in the management of pod shattering.In the present study 84 genotypes of soybean were screened for pod shattering resistance under lab condition.The pod shattering values ranged from 8.7 to 93.3 per cent.JS-335 one of the most popular variety recorded as tolerant with mean pod shattering value of 10.3 per cent.It is evident from the table that, none of the genotypes were better than the JS-335 except Himsoy-1560, which recorded 8.7 per cent mean pod shattering value.Among 84 genotypes, 20 genotypes fall under tolerant category and 32 under moderately shattering.Fifteen Indian soybean varieties were screened for pod shattering resistance and out of these three varieties viz., JS-1515, JS-1608 and JS-1625 were found resistant against pod shattering [16].Similarly, while screening for pod shattering resistance, Bragg and JS-71-05 recorded the lowest pod shattering and Punjab-1 with highest pod shattering value [12].Similar results were also reported [1,13].

Screening for rust resistance
Among many of the diseases in soybean, rust is the major fungal disease which may reduce the yield drastically.So identification of resistant sources and involving them in resistant breeding forms one of the criteria in resistant breeding programme.In the present study 84 genotypes of soybean were screened for rust resistance under natural epiphytotic condition.None of the genotypes showed immune reaction.However, genotypes EC-241778 and EC-241780 showed resistance reaction.Remaining all genotypes exhibited highly susceptible reaction.In general, over all disease incidence was very high.Similar results are reported in [9], who evaluated several soybean genotypes and varieties under natural epiphytotic condition and reported EC-392530, EC-392538, EC-392539, EC-392541, SL-423, RSC-1, RSC-2, JS-80-21 and PK-1029 as moderately resistant.Hundekar (1999) also evaluated S-22, WC-12 and 92-10 as rust resistant germplasm.Among varieties PK-1162, PK-1029, JS-80-21 and PK-1024 showed moderately resistant reaction with better yield.Basavaraja (2002) identified three useful mutants which are moderately resistant to rust among 270 induced mutant families studied in M 3 generation.Similar results were also reported by various researchers [8,10,14,15]

Screening for yellow mosaic disease
Yellow mosaic is one of the major viral diseases in India and it is causing major problem during rabi/summer in Utter Pradesh in recent years.The yield loss due to disease may range from minor to complete loss depending upon severity.So identification of resistant sources will help in optimum management and thus help in future breeding programmes.In the present study, 84 genotypes of soybean were taken for screening against yellow mosaic disease under natural conditions.None of the genotypes tested were immure to the disease.Over the entire disease incidence was high which was evident from the results as most of the genotypes fall under the category moderately susceptible to susceptible.Similar results were also reported [6,17].They screened 88 indigenous and exotic soybean genotypes in the field and found EC-107014, EC-107003 and EC-100777 resistant.

.3. Screening for yellow mosaic disease resistance
951% or more plants exhibiting symptoms highly susceptible Screening of Soybean (Glycine Max (L.) Merrill) Genotypes for Resistance to Rust, Yellow Mosaic and Pod Shattering http://dx.doi.org/10.5772/546973.

Table 1 .
Screening of soybean genotypes for pod shattering resistance

Table 2 .
Grouping of Soybean genotypes for pod shattering resistance

Table 3 .
Grouping of soybean genotypes for soybean rust resistance 84 genotypes of soybean were screened for yellow mosaic disease under natural conditions at Research Farm of Kisan (PG) College, Simbhaoli, Ghaziabad during kharif, 2008.The data presented in Table4revealed that, YMD incidence ranged from 0.95 to 90.12 per cent.Among the 84 genotypes screened lowest incidence was recorded with genotype MACS 57 (0.48%), followed by EC 241778 (0.49%).Genotypes JS 90-41 (90.12) recorded highest incidence followed by JS 76-205 (89.15%) and T 49 (86.21%).All the genotypes and their percent disease incidence are tabulated in Table5, which categorizes these genotypes based on 0-9 scale into different reaction types.It is evident from the table that none of the genotypes tested were immune or resistant.Screening of Soybean (Glycine Max (L.) Merrill) Genotypes for Resistance to Rust, Yellow Mosaic and Pod Shattering http://dx.doi.org/10.5772/54697

Table 5 .
Grouping of genotypes into different categories for soybean yellow mosaic virus resistance