Research Article
Evolution of High Yielding, Early Maturing and CLCuV Resistant Mutant of Cotton NIAB-98, Through the Use of Pollen Irradiation Approach
Nuclear Institute for Agriculture and Biology, P. 0. Box 128, Jhang Road, Faisalabad, Pakistan
The success of all conventional cotton breeding approaches is highly correlated with the genetic variability present within the existing germplasm. However if the desired trait is not present or/and linked with other undesirable traits in the existing germplasm, then the cross breeding may not be worthwhile. In such cases recombination of genes is to be sought out to achieve the desired objectives. Recombination process plays a major role to induce genetic changes and the recombination of linked genes is brought about by crossing over. Generally in eukaryotic cells radiation treatments are known to enhance crossing over in proximal region adjacent to the centromere. Thus irradiation of F1 plants especially during premeiotic stages is further known to enhance crossing over in proximal region adjacent to the centromere resulting in further enhancing the genetic variability in F2 population. Increased variability in F2M2 for quantitative traits has been reported in rice (Jalil Miah and Yamaguchi, 1965). Moreover radiation as well as several chemicals are reported to increase somatic recombinations (Vig, 1973). Exposure of seed to ionizing radiation's has resulted in creating genetic variability in different crop species and many plant breeding programmes have shown the feasibility of radiation plus selection as a direct method of varietal improvement (Carnelius, 1973; Micke et al., 1987; Iqbal et al., 1991; Iqbal et al., 1994). Irradiation of male parent pollen before cross- pollinations resulted in the induction of mutations in cotton (Pate and Duncan, 1963; Krishnaswami and Kothandaraman, 1976). The studies carried out by Aslam and Stelly (1994) and Aslam et al. (1994) and Aslam (2002) have shown that treatment of pollen with low doses of gamma rays (5 to 20 Gy) before cross-pollinations are suitable to induce useful genetic variability in cotton. The present research studies were aimed at to create genetic variability through crosses with irradiated male parent pollen, selecting the desirable recombinants from the segregating populations and their evaluation for high yield potential and wider adaptability in the cotton growing areas of Punjab for confirmation.
The well adapted and higher yielding local cotton variety NIAB-78 was crossed with an exotic line REBA-288 using irradiated male parent pollen at 10 Gy of gamma rays before cross-pollinations during the year, 1993-94. At maturity the seed cotton was collected from the bolls obtained from successful crosses and ginned to produce M0 seed. M1 population was grown from M0 seed at a spacing of 30 and 75 cm from plant to plant and row to row respectively. At maturity the seed cotton was collected from M1 population and instead of pooling one locule per boll from all the M1 plants together, we picked seed cotton one locule from each boll of each M1 plant separately. The M2 population comprising of about more than three hundred individual plants was studied and selection for the desirable mutants/recombinants was carried out. The selections from the M2 was based upon, early maturity, better plant type, higher yield and better yield components etc., along with resistance to CLCuV disease. Of these, 12 promising mutants were grown in M3 generation in replicated plant progeny test (RPT). The size of the individual plot was 0.75 x 10 m2. The breeding behaviour of these progenies was studied in M3 generation and a higher yielding progeny, PIM-76-8 was selected. The same was studied in plant progeny rows in M4 generation to confirm its higher yield potential and to see its breeding behavior/uniformity. Finally the progeny PIM-76-8 was selected from M5 and bulked for evaluation under the name of NIAB-98. During the years i.e., 1999-2002, various trials (zonal yield trials, NCVT and DCR etc., were conducted at NIAB, at farmers fields etc., for confirmation of the high yield potential and wider adaptability. Moreover various other related studies i.e., on earliness, heat tolerance, reaction towards insects and diseases particularly ClCuV disease were carried out.
Results and Discussion
The M1 generation results revealed that the plants were faster in growth and had hybrid vigour for various traits. The M1 generation plants showed resistance to CLCuV disease under severe natural disease epidemic (S-12, a highly susceptible variety had 100 % CLCuV disease infestation). It was noted that the M2 generation plant progenies were generally of varied nature and some of the individual plants possessed desirable combination of certain economic traits alongwith resistance against CLCuV disease under high disease infestation. The boll weight and yield of the promising mutants selected from M2 population ranged from 3.5-5.0 g and 211-396 g respectively. Then the mutant was evaluated in the succeeding segregating generations. The results indicated that the mutant progeny, PIM-76-8 gave 22.5% higher average yield than the prevalent standard cotton variety, CIM-443. The morphological studies carried out indicated that the plant of NIAB-98 is moderately hairy, semi-compact sympodial type with fruit bearing monopodia. It has desirable leaf foliage and medium plant stature. The length of the sympodial and monopodial and internodes of the main stem are shorter than those of the parents and prevalent commercial varieties.
Table 1: | Morphological characteristics and fruiting pattern of mutant NIAB-98 compared with other varieties of cotton |
Table 2: | Confirmation of CLCuV resistance in NIAB-98, through artificial grafting in NCVT (2000-2001) by CRI Multan/reported by PCCC, Karachi |
*- = No symptoms; += Mild; ++= Medium; +++= Severe; ** 0= Complete absence of symptoms; 1= Few small scattered vein thickening; 2= small scattered vein thickening; 3= Vein thickening involving small vein thickening; 4= Large groups of vein involved; 5= All vein involved; 6= All vein involved and severe curling |
Table 3: | Performance of mutant NIAB-98 in yield trials in comparison to standard cotton varieties at NIAB (1998-2002) |
*Rating Scale 0-5, 0= No symptoms, 5= Highly susceptible |
Table 4: | Summarized (average) yield performance (Kg/ha) of mutant NIAB-98 at farmers fields during the years 1999-2002 |
Table 5: | Yield results of NCVT-2001, DCR-2000-2000 and DCR-2000-2001 |
Table 6: | Effect of high temperature on fruit formation in NIAB-98 and other leading cotton varieties during 2001-2. |
* Average fruit formation from July - August 22, 2001. |
Table 7: | Earliness studies on NIAB-98 and other standard cotton varieties during the year, 1999 and 2000 ( average) |
Compared with the tall plants forming a canopy at the top, this medium plant (4-5.5 feet) is better suited for better photosynthetic activity and better yields. This plant type makes the agricultural operations such as pesticides spray, picking, inter-culture, etc., also easier (Table 1). The morphological characters of NIAB-98 make its growing period shorter with faster squaring quality and it matures in 145-150 days with high fruiting load to give high yield. The seeds of NIAB-98 are bold dull white and fuzzy with greenish tinge.
The results revealed that NIAB-98 was resistance to CLCuV under high inoculation in the field. The CLCuV resistance was further confirmed through artificial grafting. The results revealed that NIAB-98, not only showed resistance to CLCuV disease under field conditions, but also showed no disease symptoms even though the disease was transferred through artificial grafting (Table 2). Various trials were conducted at NIAB and on Farmers Fields and coordinated vaietal trials organized by PCCC, Karachi, and Director Cotton Research Institute, Faisalabad. The results revealed that at NIAB, on the average the NIAB -98 gave 32.0 % higher yield than CIM-443 during 1998-99 and during 1999-2000 it gave 47.2 and 37.6 % higher yield than CIM-443 and NIAB-Karishma respectively (Table 3). Whereas the increase in yield of NIAB-98 over the latest standard cotton variety CIM-482 was 27.2 % during 2000-2001 and 28.9 during 2001-2002 respectively. The trials conducted at farmer's fields; revealed that on the average ( average of 3 years) the NIAB-98 gave 21.0,16.1, 9.2, 29.9,16.9 and 11.2% higher yield over the standard varieties i.e. CIM-443, NIAB -Karishma CIM-482, CIM-446 and FH-900 respectively during the year 1999-2002 (Table 4). The NIAB-98 also had shown wider adaptability by ranking 4th in NCVT 2000-2001 and 6th and 2nd in DCR trials, 2000-2001 and 2001-2002, respectively as compared with the entire standard leading varieties (Table 5).
Table 8: | Mean population development of sucking pests and bollworms in different cotton varieties (2000-2001) |
Table 9: | Population of sucking insect pest's on various genotypes of cotton (Per leaf population) by Entomologist AARI, Faisalabad, during 2001-02 |
similar letters are not significantly different at P=0.05. |
Table 10: | Summarized-quality characters of NIAB 98, compared with other cotton varieties determined by NIAB and other fibre testing Laboratories |
Table 11: | Oil and Protein contents (%) of different cotton varieties during 2001-2002 |
*NIAB Faisalabad; ** PSC Farm, Khanewal |
The results on earliness and physiological attributes of NIAB-98, showed that the flowering started earlier in NIAB-98 and is better tolerant to high temperature as compared to other varieties (Table 6, 7). Moreover it is also apparent that NIAB-98 had shorter boll maturity period thereby confirming the earliness of NIAB-98. The results of studies carried out on relative development of sucking pests and bollworms complex on different cotton varieties during 2000-2001 indicated that NIAB-98 was comparable or some time better with respect to sucking pest's complex development than other varieties (Table 8, 9). Whereas it had relatively less infestation of bollworms and due to its early maturity it can escape the peak attack period of pink bollworm and fewer number larvae enter into diapause thus reducing the carry-over source for infestation for the next year. The fibre characteristics of NIAB-98 were tested at NIAB. The results indicated that the all value have been comparable and acceptable (Table 10). NIAB-98 has G.O.T. of 37.7%, staple length of 27.5mm, fineness of 4.9 Fg/in, strength of 93.5 TPPSI, fibre maturity 89.4% and uniformity ratio of 48.2%. The results of the studies carried out on oil and protein contents of NIAB-98 revealed that NIAB-98 had higher percentage of oil contents i.e., 24% and also protein contents i.e. 28% (Table 11) as compared to prevalent standard cotton varieties (CIM-433, CIM-446, CIM-482, CIM-473 and FH-900).
The pollen irradiation approach seem to be better than seed irradiation, since in order to create genetic variability through seed irradiation, the whole genome is to be irradiated, which ultimately disturb the whole genetic makeup of the exposed individual. Consequently the most of the changes occurring in the population are the somatic/non-heritable changes. Therefore large M2 population may be more than 12,000 individual plants is required, to select desirable mutants (Iqbal et al., 1994). Since the irradiated pollen is a germ cell and after fertilization only half of the genome of the developing zygote/embryo, receives the irradiation, hence the occurrence of major changes is minimized as observed in case of seed irradiation. The results confirmed that the pollen irradiation is a valuable technique, which can be employed to improve crop plants most effectively. Moreover incase of seed irradiation usually from each M1 plant the seed cotton from each locule per boll is collected and then pooled to have M1 seed to grow M2 population and consequently large population has to be screened for selecting the desired genotype. But through the use of pollen irradiation technique, each M1 plant has to be grown separately as plant progeny rows to develop M2 population, which facilitate to carry out selection. Since most of the progenies carried micro- mutations/point mutation due to optimal radiation dosages applied to pollen before fertilization and no major abnormalities were noticed which may help to achieve uniformity earlier as compared to seed irradiation. Moreover the male gamete is to be irradiated at low doses of gamma rays before fertilization and therefore more recombinations are brought about due to enhanced chaisemata formation/crossing over during meiotic stages of cell divisions. The results reported above have clearly illustrated that from a very small M2 population even less than 1000 plants, higher rate of mutations/recombinations was achieved through pollen irradiation. Therefore the results obtained clearly confirmed the earlier findings (Jalil and Yamaguchi, 1965, Vig, 1973, Wang, 1990). Moreover, the method of gamete treatment was found easier to apply than that of zygote/seed treatment.
Irradiation of male parent pollen before cross-pollinations resulted in the induction of mutations in cotton (Pate and Duncan, 1963; Krishnaswami and Kothandaraman, 1976). These results are in accordance with the earlier findings (Aslam and Stelly, 1994; Aslam et al., 1994; Aslam, 2000), that the treatment of pollen with of low doses of gamma rays (5 to 20 Gy) before cross-pollinations are suitable to induce useful genetic variability in cotton, G. hirsutum L.