Vitellogenin knockdown strongly affects cotton boll weevil egg viability but not the number of eggs laid by females.

Vitellogenin (Vg), a yolk protein precursor, is the primary egg nutrient source involved in insect reproduction and embryo development. The Cotton Boll weevil (CBW) Anthonomus grandis Boheman, the most important cotton pest in Americas, accumulates large amounts of Vg during reproduction. However, the precise role of this protein during embryo development in this insect remains unknown. Herein, we investigated the effects of vitellogenin (AgraVg) knockdown on the egg-laying and egg viability in A. grandis females, and also characterized morphologically the unviable eggs. AgraVg transcripts were found during all developmental stages of A. grandis, with highest abundance in females. Silencing of AgraVg culminated in a significant reduction in transcript amount, around 90%. Despite this transcriptional reduction, egg-laying was not affected in dsRNA-treated females but almost 100% of the eggs lost their viability. Eggs from dsRNA-treated females showed aberrant embryos phenotype suggesting interference at different stages of embryonic development. Unlike for other insects, the AgraVg knockdown did not affect the egg-laying ability of A. grandis, but hampered A. grandis reproduction by perturbing embryo development. We concluded that the Vg protein is essential for A. grandis reproduction and a good candidate to bio-engineer the resistance against this devastating cotton pest.

Relationship between germination and bell pepper seed structure assessed by the X-ray test

Alternative use of the X-ray test to evaluate seed quality has become increasingly diverse. This study was performed primarily to establish experimental procedures and verify the effectiveness of the X-ray test to detect damage or abnormalities in bell pepper (Capsicum annuum) seed structure associated with germination. Five seed lots each of hybrids Reinger and Sentinel were used. Two hundred seeds per lot were exposed to durations and intensities of X-radiation and visually classified into four categories according to the proportion between the area occupied by the embryo and endosperm in relation to the total cavity area in the internal seed structure, e.g. 0, 50%, 50-75% and 100%. The last category was subdivided into two others based on the occurrence of morphological abnormalities. Seed samples obtained from different X-ray categories were then submitted to germination test at 25ºC for 14 days and subsequently compared with results of the X-ray analysis. Exposure to a 10 kV radiation for 260 s was the most suitable X-ray dose for visualizing seed structure. Seeds in which the area of the internal cavity occupied by the embryo and endosperm varied from 50-75% produced abnormal seedlings or did not germinate. Full seeds (100% of the internal cavity area occupied) with abnormal structure usually originated defective seedlings. As a consequence, the classification of bell pepper seeds according to the proportion occupied by the seed content (embryo + endosperm) allowed a reliable estimation of the degree of seed physical integrity based on X-ray analysis and its association with germination performance.

Relationship between germination and bell pepper seed structure assessed by the X-ray test

Alternative use of the X-ray test to evaluate seed quality has become increasingly diverse. This study was performed primarily to establish experimental procedures and verify the effectiveness of the X-ray test to detect damage or abnormalities in bell pepper (Capsicum annuum) seed structure associated with germination. Five seed lots each of hybrids Reinger and Sentinel were used. Two hundred seeds per lot were exposed to durations and intensities of X-radiation and visually classified into four categories according to the proportion between the area occupied by the embryo and endosperm in relation to the total cavity area in the internal seed structure, e.g. 0, 50%, 50-75% and 100%. The last category was subdivided into two others based on the occurrence of morphological abnormalities. Seed samples obtained from different X-ray categories were then submitted to germination test at 25ºC for 14 days and subsequently compared with results of the X-ray analysis. Exposure to a 10 kV radiation for 260 s was the most suitable X-ray dose for visualizing seed structure. Seeds in which the area of the internal cavity occupied by the embryo and endosperm varied from 50-75% produced abnormal seedlings or did not germinate. Full seeds (100% of the internal cavity area occupied) with abnormal structure usually originated defective seedlings. As a consequence, the classification of bell pepper seeds according to the proportion occupied by the seed content (embryo + endosperm) allowed a reliable estimation of the degree of seed physical integrity based on X-ray analysis and its association with germination performance.

'Aroeira-branca' [Lithraea molleoides (Vell.) Engl. - Anacardiaceae] seed quality evaluation by the X-ray test

'Aroeira-branca', an arboreal species of great ecological and economic importance, is seed propagated and presents limitations with respect to the availability of methods for seed quality evaluation. The X-ray test has been considered of potential value because it is accurate, quick and nondestructive. In this context, the objective of this work was to verify the possibility of this test to detect damage and/or abnormalities in aroeira-branca embryos, in an attempt to correlate these anomalies to germination. Four seed lots were collected in different locations in the southern region of the State of Minas Gerais, Brazil, during 2001. The X-ray test consisted of submitting 100 seeds/lot to radiation (exposure of seeds to radiation of 13 kV/5 minutes) and classifying them according to embryo/embryo cavity proportions of 0, 50, 50-75 and 100%, with the latter class divided into normal and abnormal according to embryo morphology. The germination test was then carried out to detect possible relationships between seed anatomy and the resulting seedling/seed ratio, as revealed by radiographs. Seeds presenting an embryo/embryo cavity proportion lower than 100%, as determined by the X-ray test, did not germinate, and those presenting abnormal embryos produced abnormal seedlings or did not germinate, providing evidence that the X-ray test is effective to assess seed quality.

A aroeira-branca, espécie arbórea de grande importância ecológica e econômica, multiplica-se por sementes, as quais têm apresentado limitações quanto à disponibilidade de métodos para a avaliação da qualidade. O teste de raios-X tem se destacado por ser um método rápido, preciso e não destrutivo. Neste contexto, o presente trabalho foi realizado com o objetivo de verificar a possibilidade de uso do teste de raios-X na detecção de danos e ou anormalidades em embriões de aroeira-branca, bem como associá-los à germinação. Foram utilizados quatro lotes de sementes colhidas em áreas da região sul de Minas Gerais, no ano de 2001. Cem sementes/lote foram submetidas ao teste de raios-X, que consistiu na radiografia (condições de exposição à radiação: 13 kV/5 minutos) e classificação das sementes baseada na proporção do embrião em relação à cavidade embrionária, de 0, 50, 50-75 e 100%, sendo a última classe dividida quanto à morfologia do embrião, em normal e anormal. Em seguida, foi conduzido o teste de germinação, visando detectar possíveis correspondências entre a anatomia das sementes e as respectivas plântulas/sementes resultantes. As sementes em que a proporção embrião/cavidade embrionária foi inferior a 100% não germinaram, e aquelas pertencentes à classe radiográfica de embriões morfologicamente anormais resultaram em plântulas anormais ou sementes não germinadas, evidenciando a eficiência da técnica de raios-X para avaliar a qualidade das sementes.

'Aroeira-branca' [Lithraea molleoides (Vell.) Engl. - Anacardiaceae] seed quality evaluation by the X-ray test

'Aroeira-branca', an arboreal species of great ecological and economic importance, is seed propagated and presents limitations with respect to the availability of methods for seed quality evaluation. The X-ray test has been considered of potential value because it is accurate, quick and nondestructive. In this context, the objective of this work was to verify the possibility of this test to detect damage and/or abnormalities in aroeira-branca embryos, in an attempt to correlate these anomalies to germination. Four seed lots were collected in different locations in the southern region of the State of Minas Gerais, Brazil, during 2001. The X-ray test consisted of submitting 100 seeds/lot to radiation (exposure of seeds to radiation of 13 kV/5 minutes) and classifying them according to embryo/embryo cavity proportions of 0, 50, 50-75 and 100%, with the latter class divided into normal and abnormal according to embryo morphology. The germination test was then carried out to detect possible relationships between seed anatomy and the resulting seedling/seed ratio, as revealed by radiographs. Seeds presenting an embryo/embryo cavity proportion lower than 100%, as determined by the X-ray test, did not germinate, and those presenting abnormal embryos produced abnormal seedlings or did not germinate, providing evidence that the X-ray test is effective to assess seed quality.

A aroeira-branca, espécie arbórea de grande importância ecológica e econômica, multiplica-se por sementes, as quais têm apresentado limitações quanto à disponibilidade de métodos para a avaliação da qualidade. O teste de raios-X tem se destacado por ser um método rápido, preciso e não destrutivo. Neste contexto, o presente trabalho foi realizado com o objetivo de verificar a possibilidade de uso do teste de raios-X na detecção de danos e ou anormalidades em embriões de aroeira-branca, bem como associá-los à germinação. Foram utilizados quatro lotes de sementes colhidas em áreas da região sul de Minas Gerais, no ano de 2001. Cem sementes/lote foram submetidas ao teste de raios-X, que consistiu na radiografia (condições de exposição à radiação: 13 kV/5 minutos) e classificação das sementes baseada na proporção do embrião em relação à cavidade embrionária, de 0, 50, 50-75 e 100%, sendo a última classe dividida quanto à morfologia do embrião, em normal e anormal. Em seguida, foi conduzido o teste de germinação, visando detectar possíveis correspondências entre a anatomia das sementes e as respectivas plântulas/sementes resultantes. As sementes em que a proporção embrião/cavidade embrionária foi inferior a 100% não germinaram, e aquelas pertencentes à classe radiográfica de embriões morfologicamente anormais resultaram em plântulas anormais ou sementes não germinadas, evidenciando a eficiência da técnica de raios-X para avaliar a qualidade das sementes.