Clavigralla Tomentosicollis Research Paper

The brown pod-sucking bug, Clavigralla tomentosicollis Stäl (Hemiptera: Coreidae), causes significant damage to cultivated cowpea, Vigna unguiculata Walp, a staple crop in sub-Saharan Africa. C. tomentosicollis pierce and suck sap from cowpea pods, resulting in reduced grain yield and quality. The complete, 16,089 bp mitogenome of C. tomentosicollis encodes 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), two ribosomal RNAs (rRNAs) and an A + T rich control region, with gene order and orientation identical to that of the insect ancestral gene order. The initiation and termination codons for the PCGs used standard ATN codons and TAA or TAG codons respectively. All predicted tRNAs fold into a clover-leaf secondary structures with the exception of tRNA-Ser (AGN) with a semi-loop dihydrouridine arm. The 1509 bps A + T rich region contains a single 89 bp tandem repeat unit duplicated 3.7 times. When compared with other published Coreoidea mitogenomes, C. tomentosicollis was also highly A − T skewed, and similar in both size and A − T%; however, its longer tandem repeat within the A + T rich region was unique. The C. tomentosicollis mitogenome can serve as a foundation to combine molecular marker data with pest monitoring strategies to better understand the population dynamics of this species.

Abstract

A laboratory study was conducted to assess the relationship between feeding by the pod sucking coreid, Clavigralla tomentosicollis (Stal.), sex of the insect, number of punctures on the pod wall and damage to seeds of cowpeas, Vigna unguiculata Walp.

Females weighed an average of 55.6 mg and males about 38 mg. The daily average of seed damage and number of punctures for females were 20.4% and 3.3%, respectively; for males the values were 17.4% and 2.5%, respectively. No difference was observed in the duration of development between males and females and weight gain increased sharply after the 4th nymphal stage.

Punctures on the pod wall were highly correlated with seed damage (r = 0.88 for males and 0.76 for females). Correlations between punctures and daily weight of the insect (r = 0.19 ♀; r = 0.31 ♂) on the one hand, and seed damage and daily weight of the insect (r = 0.25 ♀; r = 0.16 ♂) on the other was very poor suggesting that presence of punctures and/or seed damage did not necessarily represent active feeding by the insect. Results from the study show that seed damage associated with feeding and/or probing activity of the insect is a good criterion to use in bioassays for the evaluation of cowpea resistance to C. tomentosicollis, and the reasons for this are given. The effect of feeding by C. tomentosicollis and ensuing seed damage on seed germination is also discussed.

Zusammenfassung

über das Ernährungsverhalten von Clavigralla tomentosicollis (Stal.) (Hem., Coreidae) und seine mögliche Verwendung zur Wirtspflanzenresistenz

Untersucht wurden die Beziehungen zwischen der Ernährung der Schotenwanze, C. tomentosicollis, dem Geschlecht der Wanze, der Anzahl von Einstichen und der Samenbeschädigung bei der Kuherbse, Vigna unguiculata. Die weiblichen Wanzen wogen im Mittel 55,6, die männlichen 38,0 mg. Die tägliche mittlere Samenbeschädigung und Zahl der Anstiche betrugen bei den Weibchen 20,4 und 3,3%, bei den Männchen 17,4 und 2,5%. Dagegen zeigte sich kein Unterschied in der Entwicklungsdauer der Geschlechter. Das Gewicht nahm nach dem 4. Nymphenstadium sprunghaft zu. Die Anstiche der Schoten waren mit den Samenbeschädigungen hoch korreliert. Dagegen waren die Korrelationen Anstiche/Körpergewicht sowie Samenbeschädigung/Körpergewicht nur schwach, woraus hervorgeht, daß die Anwesenheit von Anstichen und Samenbeschädigungen nicht notwendig die aktive Ernährung der Wanze repräsentieren. Die Ergebnisse insgesamt zeigen, daß die Samenbeschädigung, verbunden mit der Ernährung und/oder der Probiertätigkeit des Insekts, ein gutes Kriterium für die Prüfung der Resistenz von Vigna gegenüber der Wanze bilden. Die Wirkung von C. tomentosicollis im Hinblick auf die Samenkeimung wird erörtert.

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