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Restricted genetic variability in elite tropical maize germplasm has raised concerns about the potential to develop higher yielding and stress-tolerant varieties. Elite temperate germplasm has high levels of genetic diversity for yield, drought tolerance and earliness. The objective of this study was to identify temperate maize inbreds that could enhance the grain yield potential, drought tolerance and high plant density tolerance of adapted tropical germplasm. Two hundred and forty-three temperate inbreds with expired Plant Variety Protection Act certificates from the USA were crossed to three CIMMYT single-cross testers. The three-way testcrosses were evaluated under high density, optimal, low nitrogen and managed drought conditions. Among the outstanding exotic temperate inbreds were HB8229, W8304, LH198 and PJH40 from the stiff stalk group, and LH159, LH214, and LH23Ht from the non-stiff stalk group. Of the highest yielding testcrosses, 65% were heterotic group A-lines, 30% heterotic group B-lines, and 5% were AB-lines. Although the testcrosses were more susceptible to diseases, their grain yield was comparable to the commercial checks, especially under managed drought and high-density conditions. Temperate lines also induced earliness and shorter plant stature to the three-way crosses. [ABSTRACT FROM AUTHOR]

Abstract: Quality protein maize (QPM) breeding involves the combined use of the opaque-2 (o2) gene and the genetic modifiers of the o2 locus to develop cultivars with modified kernel endosperm, and increased concentrations of lysine and tryptophan. This study was designed to assess grain yield performance, endosperm modification, and protein quality and quantity under two contrasting soil nitrogen environments. A 15-parent diallel cross was evaluated under one low nitrogen stress and one optimal nitrogen environment each at Harare (Zimbabwe) and Bako (Ethiopia). Most QPM hybrids showed higher protein quality levels than the best non-QPM check under both conditions. Protein concentration tended to vary across nitrogen levels, but not endosperm type. Significant differences were found for the test of main effect (nitrogen-level) for endosperm modification and tryptophan concentration. This indicated that QPM maintains quality even under low soil nitrogen, a widespread condition in Africa. General combining ability (GCA) mean squares were highly significant for most protein quality traits for each environment and across environments whereas specific combining ability (SCA) mean squares were not significant in most cases. This indicated that additive gene effects were primarily responsible for variation of most traits evaluated and hence progeny performance can adequately be predicted on the basis of parental performance. Inbred lines P2, P4 and P12 had desirable GCA effects for endosperm modification while P1 and P3 had the best GCA for tryptophan concentration in grain. The current study suggests that hybrids with desirable endosperm modification, protein quality and stable performance under low nitrogen stress and optimal conditions can be produced with careful selection. [Copyright &y& Elsevier]

A field screening trial undertaken in Uganda showed that a number of Musa L. (Musaceae) cultivars and hybrids displayed high levels of resistance to banana weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae), while most highland banana cultivars tended to be susceptible to weevil attack. In this study, research was undertaken to determine modalities of resistance to banana weevil. Laboratory studies suggested that all cultivars were attractive to the weevil and that females freely oviposited on all cultivars. While some differences were found between cultivars in attractivity and egg numbers, these were not related to subsequent damage. Therefore, antixenosis does not appear to play an important role in host-plant resistance to banana weevil. Larval survivorship rates in living corms were, for the most part, low on resistant cultivars, suggesting that antibiosis mechanisms offer the primary avenues of resistance. In the laboratory, development was slower on some resistant cultivars although survivorship rates on excised corm material were not as well related to levels of resistance as that on living material. Sap appeared to play a minor role in reducing egg eclosion rates on some resistant cultivars. Methanol extracts from Kayinja, a resistant cultivar, inhibited larval development on corms of susceptible cultivars in the laboratory. [ABSTRACT FROM AUTHOR]

Abstract  : Potato (Solanum tuberosum L.) is a nutritious starchy tuber crop consumed as a staple food in most potato growing countries. Its productivity and production are limited by climate change; thus, it is of utmost importance to tap into the diversity of germplasm resources, therefore, diversifying the potato varieties available for production. The objectives of this study were to determine the phenotypic diversity among the selected Agricultural Research Council-Vegetable, Industrial and Medicinal Plants (ARC-VIMP) potato varieties for tuber yields and processing quality and to determine the correlation between measured traits. Two imported and 22 local potato varieties were planted in three different environments in South Africa. Significant (P < 0.001) differences in the tested varieties across all environments were observed for all measured traits. High broad-sense heritability (> 0.6) was observed for most of the traits, except for fry colour and the yield of unmarketable tubers. Nine ARC varieties and three standard varieties were associated with high tuber yield and quality traits, indicating their suitability for the fresh market and processing industry. Variety Mondial and five ARC varieties were associated with high tuber yield, indicating their suitability for the fresh market. Varieties released between 2004 and 2021 had high tuber yield, dry matter and specific gravity compared to the standard varieties and varieties released between 1980 and 1999, although there were slight differences in the magnitudes of their traits measured. These varieties could be recommended for commercial production for specific markets and for use as potential parents for further genetic improvement of the potato crop. [ABSTRACT FROM AUTHOR]