Comparison of selection indices for screening maize (Zea mays L.) germplasm for cold tolerance

Zaffar, Gul and Shikari, Asif B. and Rather, M. Ashraf and Guleria, S. K. (2005) Comparison of selection indices for screening maize (Zea mays L.) germplasm for cold tolerance. Cereal Research Communications, 33 (2-3). pp. 525-531. ISSN 0133-3720

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Abstract

The comparisons among the 6 selection indices S ₁ , S ₂ , S ₃ (simultaneous selection indices comprising of X ₁ only; X ₁ +X ₅ and X ₁ +X ₂ +X ₃ +X ₄ respectively as their component traits), S ₄ (Rank summation index), S ₅ (Baker’s standard deviation index) and S ₆ (Elston’s weight free index) were made involving 4 primary cold tolerance traits namely field emergence per cent (X ₁ ), fresh seedling root mass (X ₂ ), seedling dry weight (X ₃ ), days to 50% silk emergence (X ₅ ) along with grain yield ha ⁻¹ (X ₄ ). Highly significant rank correlations of proposed selection indices conferred the suitability in use of one index if substituted for other, to score the genotypes for selection. Selection differentials for all the indices were generally positive with respect to the traits X ₁ , X ₂ , X ₃ and X ₄ except S ₂ which, was accompanied with negative differentials for X ₂ , X ₃ and X ₄ . S ₁ was found to be an important cold tolerance trait depicting not so less differentials compared to other traits and had positive differentials under each selection criteria. Index S ₆ was efficient in selecting early silking varieties with high yield and tolerance to cold. The populations NDSM 8 WN, NDSAB (MER), NDSLC and land races GL20W and Dawar-2 showed high degree of cold tolerance among 67 genotypes evaluated and showed at par results with the C ₁₅ check which was top ranking under 5 out of 6 selection used.

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