Advanced Journal of Seed Science and Technology (AJSST) ISSN: 2812-3425, Vol. 7(2), pp. 191-210, August, 2021. © Advanced Scholars Journals

Full length Research paper

Response to selection for downy mildew resistance, grain yield, and secondary traits in three quality protein maize populations in Mozambique.

*Mariote D, ¹Laing M, ²Tongoona P and ³Derera J

 *P.O. Box. 3658, IIAM, Av. das FPLM, Maputo

^1-2-3ACCI-Universty of Kwa Zulu Natal, Pietermaritzburg campus

Corresponding Author’s E-Mail: [email protected]

Accepted 23 July, 2021

Abstract 

Downy mildew (DM) is a major problem in quality protein maize (QPM) varieties under cultivation in Mozambique. Recurrent selection was therefore initiated to improve DM resistance in three QPM populations, mainly Sussuma, ZM521Q and Pop62SRQ at Umbeluzi Research Station in Mozambique, during 2003-2006 seasons. Downy mildew disease incidence and severity were rated at four and eight weeks after infection (WAI) based on visual assessment of the whole plot. Selfed S1 progenies were selected based on FS progeny performance. Two selection cycles were formed and evaluated. Selection intensity was 50%, and 25% in cycle 1 (C1) and cycle 2 (C2), respectively. The C1 and C2 were evaluated in a randomized complete block design with three replications in 2005/6 season. Results indicated significant improvement in DM resistance from C1 to C2, with scores of 4.6-3.9 in Sussuma, 3.0-2.3 in ZM521Q and 4.0-3.3 in Pop62SRQ, respectively. Results also indicated increase in genetic variances (σ²_G) for DM from 0.069 in C1 to 0.119 in C2 in Sussuma; 0.054 in C1 to 0.1442 in C2 in ZM521Q, and from 0.097 in C1 to 0.313 in C2 in Pop62SRQ. Broad sense heritability (H²) estimates ranged from moderate to high and increased from C1 to C2 in all populations. The H² estimates were 0.63-0.76 in Sussuma; 0.60-0.63 in ZM521Q and 0.60-0.63 in Pop62SRQ. These changes were associated with an increase in yield of about 4.67% in Sussuma, 4.68% in ZM521Q and 4.47% in Pop62SRQ. There was also an improvement in flint nature of the grain with texture scores of 2.7-1.4 in Sussuma, 2.9-1.8 in ZM521Q and 2.5-1.7 in Pop62SRQ. There were no significant changes in anthesis-silking interval, plant height and number of ears plant^-1_. This study showed that S1 recurrent selection was effective in improving QPM populations for DM resistance, increasing genetic variances and broad sense heritability estimates without compromising grain yield, texture, and other important characteristics.

Keywords: Downy mildew, quality protein maize, recurrent selection, progenies, genetic variances.