Inheritance of agronomic and quality characteristics in sweet potato (Ipomoea batatas (L.) Lam.)

[摘要] English: 1. The study was undertaken to estimate genetic parameters like variancecomponents, general and specific combining ability effects, phenotypic andgenetic correlation coefficients, heritability coefficients, heterosis, genotype byenvironment interaction and genotypic stability for various characteristics of sweetpotato.2. Four male parents (Kenia, Brondal, Impala and Mafutha) were crossed in afactorial fashion with three female parents (Bosbok, Koedoe and Ribbok). Theoffspring and their parents were planted in three different environments atRoodeplaat, near Pretoria. One trial was planted under irrigation in 1998. Theother two were planted in 1999 under irrigation and rainfed conditions,respectively. Twenty-five different agronomic and quality characteristics weremeasured. The computer program AGROBASE (1997) was used to perform thedifferent analyses of variance such as the Line x Tester and additive main effectsand multiplicative interaction, and correlations.3. Significant differences were found among the averages of the parents and theiroffspring for nearly all characteristics except NMRW. The G x E interactions weresignificant for TRW, MRN, TSS, Hl, Pl, VC, lO, llT and Nl. Kenia and Mafuthawere outstanding with regard to their high dry matter content.4. The male parent Mafutha had the largest GCA effect for TRN (0.65), RFC (0.46),OMC (0.01) and HI (0.04). Impala had the largest GCA effect for TRN (0.75),Bosbok for RSC (1.55) and Kenia for OMC (0.02). No significant SCA effects werefound between the crosses for economic important characteristics.5. GCA: SCA ratios across environments for all root yield characteristics ofeconomic importance were close to unity except for TRN with a ratio of 8.6.Extremely high GCA: SCA ratios were found for LLT (81.65), VC (61.56), La(54.12), PL (44.72) and VIL (39.25).6. The VAIVG ratios were relatively high for most of the characteristics except forMRW (0.59) and TRW (0.68).7. Larger heritability coefficients were found from the female parents for RSC, RO,LVP and PP. Combined narrow and broad-sense heritabilities estimated over bothparents (h2 M+F) were negative for most economic important characteristics.Relatively high narrow-sense heritabilities were found for RFC (0.47), VL (0.46),VIL (0.46), LVP (0.45), La (0.48) and LLT (0.49). Narrow-sense heritabilityestimates by the parent-offspring regression method ranged from negative forNMRW and TRW, to 1.44 for PL. Among the characteristics of economicimportance, OMC had the highest estimate (0.66) followed by RSC (0.57) andTRN (0.54).8. Highly significant phenotypic correlation coefficients were found between OMCand TSS (0.75), TRN and MRN (0.86), VIL and VL (0.90), LLT and LO (0.84), NLand LO (0.83), NL and LLT (0.78), MRN and TRN (0.79), Hl and FW (-0.93) andHI and VL (-0.77). Extremely high and significant genetic correlations were foundbetween TRW and MRW (0.92), LVP and NMRW (0.94), TRN and NMRN (0.88),Hl and TSS (0.94), TSS and VIL (0.91), TSS and NL (0.96), OMC and Hl (0.91),OMC and PP (0.93), OMC and LLT (0.97), FW and Hl (-0.91), Hl and LL (-0.95),VL and VIL (0.94), PL and FW (0.91), TRW and LL (0.91), VC and PP (0.93), LOand LLT (0.92) and between FW and LL (0.93).9. Correlated response to selection indicates that selection for high HI is likely toincrease MRW (0.02) and MRN (0.07 - 0.08). Furthermore, selection for longvines is likely to increase TSS (0.12 - 0.22), MRW (0.06), MRN (0.11), and TRW(0.08).10.When combined across parents and environments, mid-parent heterosis wasnegative for all root yield and quality characteristics of economic importanceexcept RO, which showed a positive heterosis of 12.9%. However, positiveheterosis was found for individual crosses at some of the environments.11.The AMMI stability value (ASV) showed that the parents were less stable thantheir crosses. The cross Koedoe x Impala was ranked first for MRN, Ribbok xBrondal for TRN, Ribbok x Kenia for MRW and Ribbok x Impala for TRW. Thecross Koedoe x Impala showed significant levels of mid-parent heterosis forstability for MRN (-98.3%), Ribbok x Brondal (-89.5%) for TRN, Ribbok x Impala(-89.4%) for MRW and Ribbok x Impala (-95.4%) for TRW.

[发布机构] University of the Free State