Combining Ability Estimates from Line x Tester Mating Design in Upland Cotton Mir

Abstract: Combining abilities of cotton varieties were evaluated using a line x tester mating design, twelve hybrids which developed from 3 testers (male) and 4 lines (females). The experiment was conducted on Randomized Complete Block Design (RCBD) with three replications during 2014. The data were recorded for plant height, sympodial plant, bolls plant, boll weight and seed cotton yield plant. Chandi-95, NIA-Ufaq and Sadori displayed the highest mean performance and GCA for more or less all the traits, indicating their superiority for inclusion in future breeding programme. The crosses Chandi-95 x BT 802, Sadori x BT A-1, Sohni x BT A-1 and NIA-Ufaq x BT-802 manifested meaning full SCA effects for economic traits, which could be used either for hybrid seed programme or developing superior varieties by applying selection in late segregating generations.


INTRODUCTION
Cotton provides raw material for various agro based industries like ginning factories, oil mills, textiles and ghee industries which also provide employment to thousands of people [1].It also provides raw material to domestic cotton industry comprising 503 textile mills, 1135 ginning factories and over 5000 oil expelling units.Cotton accounts for about 11 percent of the cropped area and produces 55 percent of the domestic edible oil.It has 80 percent share in the total vegetable oil production in the country [2].Hybrid cotton seed offer many advantages over the conventional variety seed such as increase in productivity, tolerance to a biotic stresses (drought, heat, cold) and is highly responsive to inputs [3].
Cotton breeders are trying to develop varieties those well adapted to our environmental conditions and produce higher yields, higher ginning outturn percentage, better fiber quality and respond to higher fertilizer doses along with increased tolerance to complex diseases and insect pest.For breeding program, parents must be genetically superior, physiologically efficient, possess better general and specific combining ability so that they could be utilized for both variety development and commercial exploitation of heterosis for hybrid crop development.
Improvement in quantitative characters is usually based on progeny performance.In quantitative genetics, only additive genes determine progeny performance.Dominant genes, on the contrary, are specific to only genotypic value of an individual [4], thus do not contribute to the progeny from one generation to another.Plant breeders make number of crosses among inbred parents to determine type of gene actions and also proportions of genetic variances attributable to additive and dominant genes for various plant characters.In early breeding large numbers of crosses were also attempted and potential parents based on progeny performance were identified.These approaches of locating potential parents and gene functioning for various plant characters require lot of resources in terms of manpower, space and time [5].
Combining ability or productivity of crosses is the combination of potential line concerning the transmission of desirable genes to their offspring.The aptitude of combination between two parents has been classified into general combining ability, defined as the average performance of a line in a series of crosses, and specific combining ability is referred to as performance of inbred parents in specific combination [6].Kempthorne [8] introduced line x tester analysis method estimating the combining ability effects useful in selecting desirable parents and crosses for interpretation the pedigree.

MATERIALS AND METHODS
The trial was conducted at the experimental farm of Nuclear Institute of Agriculture (NIA) Tandojam to estimate the combining ability for quantitative trait in upland cotton (Gossypium hirsutum L).The experimental material i.e. seeds of F 1 hybrid along with their parents was sown in the Randomized Complete Block Design during kharif season 2012.The experimental material comprised four lines (Chandi, Sohni, Sadori, NIA Ufaq) and three testers (BT 802, BT 703, BT A1) and their 12 F 1 hybrids.The trait studied were Plant height (cm), Sympodial branches plant -1, Boll plant -1, Boll weight (g), Seed cotton yield plant -1 .
The collected data was be subjected to the statistical analysis (ANOVA) after [7] Gomez and Gomez (1984) and combining ability by Kempthorne [8].

RESULTS AND DISCUSSIONS
Mean performance for formulating the breeding strategy of any crop it is important to know the genetics of the genotype/varieties to be included in the breeding programme.In this experiment the general and specific combining ability effects of 7 parents and their 12 crosses were determined.Mean squares and the mean performance of parents (lines and testers) including their 12 F 1 hybrids is presented in Tables 1 & 2 respectively.Table 1 reveals that genotypes were highly significant at 0.01 level of probability for plant height, number of sympodial plant -1 , number of bolls plant -1 , boll weight, seed cotton yield plant -1 , which states that there were considerable variation among parents and their F 1 hybrids.

Combining Ability (Variance and Effects)
The general combining ability (GCA), Specific combining ability (SCA) effects are obtainable in Tables 1, 3 and 4 correspondingly.Whereas the mean square of GCA present in Table 1 indicated the significant dissimilarity for all the characters.Mean square of SCA and reciprocals were also significant which indicates additive and non additive type of gene action apprehensive in the manifestation of character under study.Several studies have been conducted to guess the gene action for yield and yield contributing characters.However, they reported inconsistent results including non-additive [9,10].

General Combining Ability (GCA)
The perusal of Table 3 shows that among parents, lines Chandi (0.99), Sadori (0.647) and NIA-Ufaq (1.613) and in case of testers BT 703 (1.77) are the parents that manifested positive GCA effects for plant height and Sohni showed negative effect (-3.25) for plant height hence suggesting that in breeding programme for development of tall plant height and dwarf plant these varieties mentioned above would be useful.Lines Chandi (1.36) and NIA Ufaq (1.44) showed significant GCA effects pertaining to number of sympodial branches plant -1 .Among testers BT-703 (0.40) genotypes displayed significant positive effects for number of sympodial branches plant -1 .And BT A-1 and BT-802 exhibited significant negative GCA effects for number of sympodia branches plant -1 . So far the .Two pollen parents i.e.BT 802 (1.27) and BT 703 (4.78) exhibited positive GCA effects.BT A-1 showed significant negative GCA effect for seed cotton yield plant 1 .These results are in accordance with the findings of [11]

Specific Combining Ability (SCA)
Table 4 shows that the F 1 among hybrids Sadori x BT A-1 manifested significant positive SCA effects, while, remaining hybrids like Sohni x BT-801 and NIA-Ufaq x BT A-1 recorded negative SCA effects for plant height.So far trait number of sympodial branches plant -1 is concerned, out of twelve crosses only eight hybrids manifested significant positive SCA effect, while, for remaining four crosses negative SCA effects were recorded.While as trait number of bolls plant-1 concerned hybrids i.e.Chandi x BT 802 (4), Sadori x BT A-1 (3) and Sohni x BT-A1 (4) expressed significant positive SCA effect for number of bolls plant -1 .
Regarding hybrids i.e.Chandi x BT A-1 (0.1), NIA Ufaq x BT 703 (0.4) and NIA Ufaq x BT A1 (0.4) showed significant positive SCA effects for the character boll weight.Seed cotton yield is very important character and is a resultant of so many variables.The hybrids, which manifested significant positive SCA, effect for the character seed cotton yield plant

CONCLUSIONS
For general combining ability effects, line Chandi showed highest effects for seed cotton yield along with more than two yield contributing characters.In case of testers BT-703 showed highest effects for seed cotton yield and more than one yield contributing characters.BT 703 showed good general combiner for number of bolls plant -1 , and seed cotton yield plant -1 .Whereas for specific combining ability effects the cross Chandi x BT 802 showed seed cotton yield plant -1 and Chandi x BT 703 revealed best specific combiner followed by Sadori x BT A-1 for number of bolls plant -1 , and seed cotton yield plant -1 .
-1 are important from viewpoint of framing future breeding strategy.Keeping in view the importance of such hybrids in present study, Chandi x BT 802 (8) and Sadori x BT A-1 (7) attract the attention of plant breeder because they manifested significant positive SCA effects for the character seed cotton yield plant -1 .Present results are in accordance with the findings of [11] Banumathy et al. (2001), [18] El-Adl et al. (2001), [19] Pedrosa et al. (2001),[20]

Table 1 : Mean Squares for Seed Cotton Yield and its Components of Gossypium hirsutum L.
* = Significant at 5% level of Probability, ** = Significant at 1% level of Probability , NS = Non Significant.