Pollen–style compatibility in cashew (Anacardium occidentale L.)

Abstract

The role of pollen-stigma interaction and pollen tube growth as a measure of genetic compatibility was studied in eleven clones of cashew under a tropical rainforest ecology in Southwestern Nigeria between 1999 and 2002. Diallel cross of the clones showed that 55.00% of the cross-pollinated crosses showed high pollen cross-compatibility (CC) indicating moderate genetic distance in the population. About 54.55% of the clones showed evidence of selfcompatibility, therefore confirming that cashew is self-fertile. Cytological examination however suggests possible postzygotic self-incompatibility in the crop as no evidence of tube growth inhibition was recorded in both cross-and self-pollinated styles. Correlation between maternal compatibility (pollen recipients) and fruit set shows that more attention need to be focused in this direction during selection. Based on the data from this study, the use of combinations of floral quality characteristics like high pollen fertility, prolific flowering, and high flower sex ratio plus high cross-compatibility as reliable selection criteria for cashew yield improvement is therefore suggested.

Genetic Diversity of Nigerian Cashew Germplasm

“…Although there are divergent opinions on the ploidy status of the occidentale species, the study revealed that most genotypes had 42 chromosomes (Aliyu and Awopetu, 2007c) and could be tentatively described as 2x = 42 for a diploid species. And that cashew karyotypes are usually symmetric and less divergent, with mainly metacentric and submetacentrics pairs (Aliyu and Awopetu, 2007c).…”

“…Although there are divergent opinions on the ploidy status of the occidentale species, the study revealed that most genotypes had 42 chromosomes (Aliyu and Awopetu, 2007c) and could be tentatively described as 2x = 42 for a diploid species. And that cashew karyotypes are usually symmetric and less divergent, with mainly metacentric and submetacentrics pairs (Aliyu and Awopetu, 2007c). There were similarity in the morphology, number and behavior of the chromosomes among genotypes from different sources of introduction, which could imply common progenitors and slow mutation rate (chromosomal) among the existing occidentale.…”

“…Apart from multilocational evaluation of most of the superior materials identified in the characterization exercise, the breeding plan included exploitation of heterosis between the highly prolific, but small fruits and very low productive and extra large fruit trees through controlled hybridization and in vitro embryo culture, where necessary. Less impediment is expected from the hybridization exercise because of the high cross-compatibility in cashew (Aliyu, 2007(Aliyu, , 2008, albeit, that the environmental conditions are favourable. …”

Compatibility and fruit-set in cashew (Anacardium occidentale L.)

“…Although Xowering commences as early as September, pollination is often delayed until the peak of Xowering between October and January in the region (Akinwale 1992;Aliyu and Awopetu 2003), to ensure availability of enough hermaphrodite Xowers for all kind of crosses. It is important to mention that studies on pollen fertility, Xoral characteristics, and pollen-style compatibility of these clones have been reported (Aliyu 2007). Standard procedure for cashew hybridization is yet to be developed in the region, however, a modiWed method of Sedgley and Attanayake (1988) described below produced appreciable results.…”

Reproductive barriers in the intergeneric hybridization between Chrysanthemum grandiflorum (Ramat.) Kitam. and Ajania przewalskii Poljak. (Asteraceae)

“…The barriers are generally divided into the pre-and post-fertilization barriers, characterized usually by incongruity (incompatibility) and hybrid breakdown (embryo abortion), respectively (Li and Zhu 1986;Raghavan 2007;Ram et al 2007). Pollen-pistil interaction was thought as a useful signal for compatibility (Aliyu 2007;Li and Ma 2006). Few germinated pollens, twisted and extended pollen tubes, and deposited callose on the stigmatic surface were thought represented cross incompatibility (Dumas and Knox 1983;Ram et al 2007;Vervaeke et al 2001).…”