Genetic analysis of yield and flesh colour in sweetpotato

Pre-breeding information on the inheritance mechanism of important sweetpotato ( Ipomoea batatas L.) agronomic traits is still limited. This study aimed at assessing the inheritance of five sweetpotato agronomic traits, viz. marketable fresh root yield (MFRY) and number (MNR), total fresh root yield (TFRY) and number (TNR) and root \u3b2-carotene content (RBCC). A 5 x 5 full diallel was performed and F1 progenies, evaluated in two environments alongside the parents. The data were subjected to ANOVA and DiallelSAS-05 Griffing\u2019s method 1. Simple Sequence Repeat (SSR) based genetic distance and cluster analysis were performed on the parental lines using Jaccard\u2019s coefficient and the unweighted pair group method with arithmetic averages (UPGMA). Significant differences (P<0.01) were detected among the genotypes for MFRY, MNR, TFRY, TNR and RBCC. Significant general and specific combining ability (P<0.01) effects were observed for all five traits. Additive gene action was predominantly involved in the inheritance of these traits. High broad sense heritability values were observed for the four yield parameters and for RBCC. The Jaccard\u2019s similarity coefficient indicated moderate to low genetic similarity distances among the parents, implying high diversity. The knowledge on the inheritance and diversity of the parental genotypes enables more effective choice of parents in breeding improved varieties.Les informations pr\ue9liminaires sur le mode de transmission des caract\ue8res agronomiques importants chez la patate douce ( Ipomoea batatas L.) sont encore tr\ue8s limit\ue9es. Cette \ue9tude vise \ue0 \ue9valuer la transmission de cinq traits agronomiques chez la patate douce. viz. Le rendement de tubercules fra\ueeches \ue0 valeur marchande (MFRY) et leur nombre (MNR), le rendement total de tubercules frais (TFRY) et leur nombre (TNR), de m\ueame que la teneur en \u3b2-carotene des tubercules (RBCC). Une s\ue9rie de croisement diallel 5 x 5 avec croisements r\ue9ciproques a \ue9t\ue9 r\ue9alis\ue9e et les descendants de g\ue9n\ue9ration F1 ont \ue9t\ue9 \ue9valu\ue9s ensemble avec les parents dans deux environnements. Les donn\ue9es collect\ue9es ont \ue9t\ue9 soumises \ue0 une analyse de variances et \ue0 une analyse DiallelSAS-05 m\ue9thode 1 de Griffing. Les distances g\ue9n\ue9tiques bas\ue9es sur des R\ue9p\ue9titions de S\ue9quences Simples (SSR) a \ue9t\ue9 calcul\ue9es et une classification num\ue9rique \ue0 \ue9t\ue9 r\ue9alis\ue9e sur les lign\ue9es parentales. Le coefficient de Jaccard et la m\ue9thode des paires-groupes non pond\ue9r\ue9s avec la moyenne arithm\ue9tique (UPGMA) ont \ue9t\ue9 utilis\ue9es \ue0 cet effet. Des diff\ue9rences significatives (P<0.01) ont \ue9t\ue9 observ\ue9es entre les g\ue9notypes pour MFRY, MNR, TFRY, TNR et RBCC. Des effets significatifs de l\u2019habilet\ue9 de combinaison g\ue9n\ue9rale (P<0.01) ont \ue9t\ue9 observ\ue9s sur tous les 5 traits. L\u2019effet additif des g\ue8nes \ue9tait pr\ue9dominant. Des valeurs d\u2019h\ue9ritabilit\ue9 au sens large ont \ue9t\ue9 observ\ue9es pour quatre param\ue8tres de rendements en tubercules et pour RBCC. Le coefficient de similarit\ue9 de Jaccard a indiqu\ue9 une des distances de similarit\ue9 g\ue9n\ue9tique faibles ou mod\ue9r\ue9es entre les parents, ce qui sugg\ue8re une grande diversit\ue9. Les connaissances sur le mode transmission et la diversit\ue9 des lign\ue9es parentales permet des choix plus efficients des parents \ue0 utiliser dans un programme d\u2019am\ue9lioration g\ue9n\ue9tique

Genome-wide association analysis of a stemborer egg induced “call‑for‑help” defence trait in maize

Published online: 08 Jul 2020Tritrophic interactions allow plants to recruit natural enemies for protection against herbivory. Here we investigated genetic variability in induced responses to stemborer egg-laying in maize Zea mays (L.) (Poaceae). We conducted a genome wide association study (GWAS) of 146 maize genotypes comprising of landraces, inbred lines and commercial hybrids. Plants were phenotyped in bioassays measuring parasitic wasp Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) attraction to volatiles collected from plants exposed to stemborer Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) eggs. Genotyping-by-sequencing was used to generate maize germplasm SNP data for GWAS. The egg-induced parasitoid attraction trait was more common in landraces than in improved inbred lines and hybrids. GWAS identified 101 marker-trait associations (MTAs), some of which were adjacent to genes involved in the JA-defence pathway (opr7, aos1, 2, 3), terpene biosynthesis (fps3, tps2, 3, 4, 5, 7, 9, 10), benzoxazinone synthesis (bx7, 9) and known resistance genes (e.g. maize insect resistance 1, mir1). Intriguingly, there was also association with a transmembrane protein kinase that may function as a receptor for the egg elicitor and other genes implicated in early plant defence signalling. We report maize genomic regions associated with indirect defence and provide a valuable resource for future studies of tritrophic interactions in maize. The markers identified may facilitate selection of indirect defence by maize breeders

Pigeonpea breeding in eastern and southern Africa: challenges and opportunities

Pigeonpea (Cajanus cajan [L.] Millspaugh) is an important multipurpose grain legume crop primarily grown in tropical and subtropical areas of Asia, Africa and Latin America. In Africa, the crop is grown for several purposes including food security, income generation, livestock feed and in agroforestry. Production in Eastern and Southern Africa (ESA) is however faced with many challenges including limited use of high-yielding cultivars, diseases and pests, drought, under-investment in research and lack of scientific expertise. The aim of this review is to highlight the challenges facing pigeonpea breeding research in ESA and the existing opportunities for improving the overall pigeonpea subsector in the region. We discuss the potential of the recently available pigeonpea genomic resources for accelerated molecular breeding, the prospects for conventional breeding and commercial hybrid pigeonpea, and the relevant seed policies, among others, which are viewed as opportunities to enhance pigeonpea productivity