Self-incompatibility in the Iranian Almond Cultivar ‘Mamaei’ Using Pollen Tube Growth, Fruit Set and PCR Technique

Abstract

Self-incompatibility has been studied by using controlled pollination, pollen tube growth and PCR methods in the Iranian almond ‘Mamaei.'. Pollen tube growth and fruit set following self and cross-pollination treatments were evaluated. The percentage of initial and final fruit set was determined for each treatment at 30 and 60 days after controlled pollination. Pollen germination and pollen tube growth were assessed by fluorescence microscopy at different times after self and cross pollination. Results showed that the percentage of the final fruit set was 0% after self-pollination, while values of 16.34%, 17.22%, 19.12%, and 21.15% were determined after cross-pollination with ‘Azar', ‘Rabie', ‘Shahrood-21', and ‘Sefied' cultivars as pollen sources, respectively. After 192 hours, observation of pollen tube growth showed that the percentage of reached pollen tubes at the style base from cross-pollination was significant but there were not any reached pollen tubes from self-pollination. According to the results of controlled pollination and pollen tube growth ‘Mamaei' is self-incompatible. S-RNase assay was used to confirm these results. PCR amplification of genomic DNA from ‘Mamaei' with EM-PC2consFD and EM-PC3consRD primers revealed the presence of two DNA fragments of sizes around 850 bp and 1250 bp on agarose gels. The size of the smaller fragment is similar to that of S25 almond RNase, while the size of the other fragment is different from all S1-S30 RNase alleles. S-genotype can be regarded as S25S x , with Sx being a new SRNase allele.