Abstract: One mutant variety Shua-92 and two mutants of rice, derived through mutation breeding from the two standard varieties IR8 and Pokkali, were evaluated for two years for their yield performance in salt affected soils with pH 7.63 to 7.68 and EC 7.11 to 8.0 dSm-1. The mutant variety Shua-92 produced 40 and 49% higher paddy yield on salt affected soils than the famous salt tolerant varieties Nona Bokra and Pokkali.
Introduction
The predominate constrain in rice production is soil salinity in Pakistan because the area ranging from 2.2 to 6.5 million hectares have become saline and 40000 hectares of fertile lands are becoming saline annually (Gareth and John, 1986). This is the most serious problem in Sindh province, where about 48% of the cultivated areas have been affected one way or other. This situation is becoming worse day by day (Aslam et al., 1987; Boje-Klein, 1986; Bui and Do, 1988; Gregorio and Senadhira, 1993; Jones, 1985; Mishra, 1990; Narayanan and Rangasamy, 1990; Yamanouchi et al., 1987; Massoud, 1974; Akber, 1986, 1987).
Many physico-chemical and biological techniques are under investigations for the reclamation of such salt affected soils in the country. Breeding for salt tolerance of rice varieties seems to be one of the most promising solutions for utilizing such soils. Exploitation of salt tolerant rice varieties had been in progress since 1943 in the sub-continent, but those rice varieties were generally low yielding. Salt affected lands provide avenues for testing rice genotypes for tolerance to salinity. As a consequence, sustained and profitable production of rice crop on salt affected soil is only possible by evolving the salt tolerant varieties, which possess high yield, early maturity and other desirable characteristics through the use of induced mutation.
Induced mutations have been utilized for creation of genetic variability for the selection of mutant varieties with improved agronomic traits (Micke et al., 1990; Hu, 1991; Maluszynske et al., 1991; Baloch et al., 1999; Baloch et al., 2001, 2002). The study was therefore, carried out to assess the performance for yield and yield components of mutation along with their parents and check varieties under saline conditions.
Material and Methods
Two mutants (IR8-202 and Pokkali-M) and one mutant variety (Shua-92) of rice, developed from varieties IR8 and Pokkali through mutation breeding, were tested at Nuclear Institute of Agriculture Farm, Tandojam, during Kharif 1998 and 1999 for grain yield and yield components under the saline conditions along with well known salt tolerant rice varieties (Nona Bokra and Pokkali) and check variety (DR-83). The layout of the experiment was 4 times replicated randomized complete block designed (RCBD) design. The plot size was 5x3 m2. Soil of the experimental area was analyzed for pH (7.68 and 8.63) and EC (7.11 and 8.00) during 1998 and 1999. The data for paddy yield and yield components were recorded at maturity, except 50% heading date. The data were analyzed according to Gomez and Gomez (1984) and mean values were compared by DMR test.
Results and Discussion
The performance of varieties with respect to days to heading, plant height, number of fertile panicle per plant, number of fertile grains per panicle, fertility percentage per panicle, 1000-grains weight, grain yield per plant and grain yield kg ha-1 were significantly (P<0.05) different from each other in both the years. The salinity affected the grain formation more than the vegetative growth as reported by Bari and Hamid (1988) and Akber (1986). The mutant of pokkali, headed earlier (112 days) followed by the variety DR83 (113.50 days) as compared with the five other genotypes during 1998 (Table 1).
Results indicated that the mutant variety Shua-92 was significantly (P<0.05) shorter in stature (71.11 cm2), higher in fertile panicles per plant (16.33), fertile grain per panicle (129.50), panicle fertility (96.00), 1000-grains weight (24.24 g), grain yield per plant (28.11 g) and paddy yield kg ha-1 (4467) than salt tolerant varieties Pokkali and Nona bokra.
| Table 1: | Performances of rice mutants/varieties for yield and yield components under saline conditions during 1998 |
| Table 2: | Performances of rice mutants/varieties for yield and yield components under saline conditions during 1999 |
| Table 3: | Average performances of the two years of rice mutants/varieties for yield and yield components under saline conditions during 1998 and 1999 |
| Means followed by the same letters are not significantly different from each other at 5% level of significance | |
This mutant variety showed an increase of 43 and 31% in fertile panicles per plant, 29 and 22% in fertile grains per panicle, 4 and 3% in panicle fertility percentage, seed index 2 and 0.4% in 1000-grains weight, 32 and 36% in grain yield per plant and 46 and 39% in paddy yield per ha-1 over pokkali and Nona Bokra, respectively. Salinity significantly reduced plant height, root length and biomass in rice cultivars indicated by Salim, et al. (1990). Results of the second year (1999) head confirmed that the mutant Pokkali-M was found early in heading (111.5 days) (Table 2). The mutant variety Shua-92 again produced significantly (P< 0.05) shorter in stature (69.34 cm), higher in fertile penicle per plant (15.51), fertile grain per penicle (124.25), penicle fertility (94.95%), 1000-grains weight (24.21 g), grain yield per plant (27.96 g) and paddy yield kg ha-1 (4580) than salt tolerant varieties Pokkali and Nona-Bokra. This mutant variety showed an increase of 14 and 389% in fertile penicle per plant, 30 and 23% in fertile grain per penicle, 4 and 3% in penicle fertility, 3 and 0.3% in seed index per 1000-grains weight, 30 and 25% in grain yield per plant and 51 and 42% in paddy yield ha-1 over the well known designated salt tolerant varieties Pokkali and Nona-Bokra, respectively.
Pooled averages of two years showed significant differences (P< 0.05) among the six genotypes under evaluation (Table 3). The mutant Pokkali-M possessed earliness in days to heading (111.75 days) among the other genotypes. While the mutant variety Shua-92 maintain its superiority in various characteristics, such as found shorter in plant height (70.23 cm), higher number of fertile penicles per plant (15.92), more fertile grains per penicle (126.87), high penicle fertility(97.47%), having heavy thousand grain weight (24.23 g), high plant yield (28.03 g) and produced higher paddy yield of 4524 kg ha-1. The mutant variety Shua-92, showed an increase of 29 and 34% in fertile penicles per plant 29 and 22% in fertile grains per penicle, 4 and 3% in fertility percentage per penicle, 2 and 0.35% in seed index per 1000-grains weight, 30 and 25% in grain yield per plant and 49 and 41% in paddy yield ha-1 than the mother variety, Pokkali and Nona-Bokra, respectively.
It is evident from results of 2 years presented here that there are marked differences in relative salt tolerance among the varieties and mutants tested under saline conditions of pH 7.68 with EC 7.11 dSm-1 had produced higher values for yield parameters than the higher pH 8.63 with EC 8.00 dSm-1. These studies suggest that the induced mutation can be successfully employed not only for high yield, but also for induction of salt tolerance in rice.
Acknowledgment
Authors are indebted to Scientists of Soil Science Division, Nuclear Institute of Agriculture, Tandojam, for the soil analysis.