Genetic variability for yield and quality characteristics in South African cotton germplasm (Gossypium hirsutum L.)

[摘要] English: The objective of this research was to study the genetic variability in South Africancotton germplasm and to identify superior parental lines for the improvement ofyield and quality characteristics.2 Six parental lines (Irco, Palala, OR27, 2131-2-5, DPAc90 and Sicala) werecrossed in diallel fashion. The parents and their F1-offspring were planted in fourexperiments at two locations, Rustenburg and Loskop, in two successive years,1997/1998 and 1998/1999. Twenty agronomic and yield characteristics weremeasured. The data for each characteristic were subjected to a diallel analysis,using the computer program Agrobase.3 Significant mean differences were found among the parental lines and theirF1-offspring for most of the characteristics measured at both locations, duringthe two successive years. The only exceptions were SI and LB. On average,Palala and Sicala proved to be the best yielders at Rustenburg, while Ircoyielded the best at Loskop. Sicala proved to be the best for FL in bothenvironments, while OR27 was on average the best for FS at both Rustenburgand Loskop. Palala was the best for FU at Loskop, while bath Irco and 2131-2-5ranked the best at Rustenburg. For the character MC, all the parents were withinthe acceptable range of 3.5 - 4.5.4 OR27 proved to be the best combiner for yield and most of the yieldcomponents, at both Rustenburg and Loskop. The parental line Sicala proved tobe the best general combiner for fibre length, while OR27 was the best generalcombiner for fibre strength and fibre uniformity at both locations. Parental linesDPAc90 and Irco were the best general combiners for MC at Rustenburg andLoskop respectively.5 The G.C.A.:S.C.A. ratios were close to unity for most of the characteristics,including yield. Some of the characteristics, such as HC (31.6 - 46.8), GOT2 (1.7- 17.3), FS (4.6 - 15.7) and FL (2.9 - 14.4) had relatively high G.C.A.:S.C.A.ratios.6 Extremely high broad sense heritabilities were found for HC (0.92 - 0.98), FL(0.92 - 0.95) and GOT2 (0.77 - 0.93). Extremely high narrow sense heritabilitywas found for HC (0.88 - 0.92), and relatively high values were also computedfor FL (0.32 - 0.77), GOT2 (0.42 - 0.87), and FS (0.48 - 0.63).7 Extremely high significant genetic correlations were computed between SCYPand LYP (0.97), SCYPLT and LYP (0.97), SCYPLT and LYPLT (0.98), SCYPand HC (0.98), LYP and HC (0.97), SCYP and TBF (0.96), SI and U (0.98) andFL and FS (0.97).8 Relatively high positive correlated response was found between SCYPL TandGOT2, U, LB, TBF and UHB in bath trials at Rustenburg. In the trials planted atLoskop characteristics like SCYP, SCYPL T, LYP and HC, had relatively high,positive correlated response with most of the other characteristics. High negativecorrelated response was found between SCYP and GOT, BS, HC and FL in theLoskop trials, while LYP had a negative response with GOT and BS.9 Mid-parent as well as high or best parent heterosis were highly positive for SCYPand LYP, in most of the crosses. The cross Sicalaxlrco, showed on average thehighest amount of heterosis at Rustenburg and Loskop during 1997/98 season.The amount of heterosis for SCYPL Tand LYPL T varies from large negative tolarge positive values.

[发布机构] University of the Free State