Line × Tester Analysis for Earliness Yield and Yield Contributing Traits in Gossypium hirsutum L .

The present study was carried out at Agriculture Research Institute (ARI) Tando Jam during 2016. The experimental material consisted of six lines viz., CRIS-134, Sindh-1, Sadori, Malmal, IR-901 and three testers; Bt-3701, Bt-121 and CIM-534.The crosses were made in line × tester mating design. F1 hybrids along with parents were sown in Randomized Complete Block Design with four replications in 2016. Seven yield and early maturing traits was recorded like, days to 1st flowering, days to 75% boll opening, plant height(cm), sympodial branches plant, bolls plant, seed cotton yield(g) and lint (%) for estimating of combining ability. The analysis of variance showed that genotypes, crosses, parents, parent vs crosses, lines, testers and line × tester were significant which demonstrated that genetic difference were present in genotypes for various yield and early maturing parameters. Among the lines, Sindh-1, CRIS-134 and testers, Bt-121 and Bt-3701 were best combiners and F1 hybrids like CRIS-134 × Bt-3701, Malmal × Bt-3701, CRIS-134 × Bt-121 were best combiners for all characters.


INTRODUCTION
Cotton (Gossypium hirsutum L.) is a cash crop of Pakistan. It is grown chiefly for its fiber which is used in the manufacture of cloth for mankind and also used for several other purposes such as for making threads for mixing with other fibers and for extraction of oil from cotton seed. All these uses give a high industrial value to this crop and as such a handsome remuneration to the growers. Cotton is grown almost all over the world from times immemorial and perhaps earlier that the time when Peruvian mummies were clothed in it. At present cotton is grown all over the world, i.e. in India, USA, Russia, China, Brazil, Egypt, Pakistan, Turkey, Mexico and Sudan are leading cotton growing countries. Cotton is most important fiber crop which plays an important role in economic and social affairs of people. It is also an important cash crop of Pakistan known as "white gold". It accounts for 8.2 percent of the value added in agriculture and about 3.2 percent to GDP; around two thirds of the country's export earnings are from the cotton made-up and textiles which adds over $2.5 billion to the national economy; while hundreds of ginning factories and textile mills in the country heavily depends upon cotton. Pakistan is the fourth largest producer of cotton in the world, with average production of 1,610 TMT (Thousand Metric Ton). Pakistan is also the fourth largest consumer of cotton, with average consumption of 1,573 TMT. An average Pakistan imports 92 TMT and exports 98 TMT. The province of Punjab accounts for the majority of the nation's production, producing 85 percent of Pakistan's total cotton, while the province of Sindh produces the other 15% of Pakistan's cotton.
There are many factors which affect the yield of cotton crop such as plant height, number of fruiting branches, number of bolls plant -1 , boll weight, seed index, G.O.T% etc. It is desirable for developing new cotton genotypes because they have strong relationship between yield and its various components which will facilitate to cotton breeders in selection of plants with desirable characteristics. Early maturing varieties increased the possibility that harvest can be completed before cold and rainy weather and also prevent from many pest attacks. In other way early maturity of cotton is preferred because of decreasing inputs of fertilizer, irrigation, crop protection and providing proper time for rotation of the other crops [1][2][3]. The main objective for a plant breeder is to evolve high yielding varieties.

MATERIALS AND METHODS
The present research was conceded at Cotton Section Agriculture Research Institute (ARI) Tando Jam during 2016. The experimental material consist five lines viz., CRIS-134, Sindh-1, Sadori, Malmal, IR-901 and three testers; Bt-3701, Bt-121 and CIM-534 were crossed in line × tester mating design to produce fifteen F 1 hybrids. These hybrids along with parents were grown in Randomized Complete Block Design with four replications at Cotton Section, Agriculture Research Institute Tandojam during 2016. All the cultural practices were done as recommended for cotton crop. The observation were recorded for days to 1st flowering, days to 50% boll opening, plant height (cm), sympodial branches plant -1 , number of bolls plant -1 , seed cotton yield -1 (g) and ginning out turn (%). The collected data were analyzed for analysis of variance through Statistix 8.1 computer software. Whereas combining ability will be estimated according to [4] and adopted by [5].

RESULTS AND DISCUSSION
The analysis of variance showed that genotypes, hybrids, parents, parent vs hybrids, lines, testers and line × tester were significant for days to 1 st flowering, days to 50% boll opening, plant height, sympodial branches plant -1 , number of bolls plant -1 , seed cotton yield, and ginning out turn % ( Table 1). The combining ability effects in the form of gene action it is important. Whereas σ 2 GCA/ σ 2 SCA ratio was more than one which exhibited that over-dominant type of gene action for characters it is indicated that heterozygous were more important. Similar results were reported by [6][7][8] they also reported over dominant type of gene action for controlling the traits.
For days to initial flowering was varied 44.00 (Sindh-1) to 54.00 days Malmal and in F 1 hybrids 44.00 (CRIS-134 × Bt-3701) to 53.50 (Sindh-1 × CIM-534) which indicated 0.5 days difference was observed in F 1 hybrids as compare to parents. The best general combiner among lines, CRIS-134 and Sindh-1 revealed negative GCA effects of -3.25 and -0.25 which was attractive effects for earliness parameters whereas, maximum GCA effects (1.42) were given by line Sadori and Malmal which indicated lateness Table 3. However, tester Bt-3701 also recorded negative GCA effects (-1.18) for days to initial flowering and female line CRIS-134 (-3.25) negative GCA effects was showed this trait. The SCA effect of days to initial flowering was mentioned in Table 4. Six F 1 hybrids recorded negative SCA effects out of fifteen F 1 hybrids. Top three negative scorers were Malmal × IR-901 (-3.47) CRIS-134 × CIM-534(-2.30) and CRIS-134 × Bt-3701 (-2.15) for days to initial flowering while Sadori × IR-901 showed highest SCA effects (2.93) for this trait. Similar results were obtained by [7,9,10,11] who reported negative GCA and SCA effects for earlier flowering.
These lines set minimum number of sympodial branches whereas, Sadori and Bt-121 exhibited positive GCA effects (3.96 and 0.24) for this trait and set more number of sympodial branches whereas, tester CIM-534 recorded highest GCA effects (1.40) for this trait presented in Table 3. However, SCA effects showed that eight F 1 hybrids manifested negative SCA effects and seven showed positive SCA effects for number of sympodial branches plant -1 ( These results suggested that above parents and hybrids should be preferred for developing high yielding varieties through selection in later generation. Similar results were obtained by [11][12][13][14][15][16][17]  Our results are confirmed with [6,[8][9][10][12][13][14][15] they reported that seed cotton yield was controlled by additive and non-additive variance hence both (GCA and SCA) the variances was very important.