*Microgametophytic Selection as a Way to Improve Drought Tolerance in Cultivated Plants DOI: http://dx.doi.org/10.5772/intechopen.102735*

determined by the relative length and dry weight of germinal roots after seed germination in sucrose solution. At the same time, it was assumed that those inbred lines were contrasting at the level of male gametophyte.

To carry out microgametophytic selection for drought resistance, a hybrid was taken obtained from crossing the morphological mutants of ZL 9 and ZL 102 sunflower lines developed at the Institute of Oilseed Crops of NAAS (Zaporozhye, Ukraine). In addition to different resistance to drought, one mutant line was characterized by chlorophyll deficiency of the "*virescent*" type at the top of the seedling, and the other one had leaves with fan venation. Both mutant traits are easily identified at the seedling stage. These inherited mutant traits were the result of our long-term research on chemical mutagenesis in sunflower [19, 20]. The presence of such "marker" traits in the parental components of the *F*1 hybrid made it possible to unambiguously characterize the genetic structure of the *F*2 segregating population.

The modified technique, proposed by Patil et al. for sorghum, was taken into account to select male gametophytes resistant to lack of moisture *in vivo* during pollen germination and pollen tube growth [21]. In the experiment, the stigmas of emasculated inflorescences were moistened with 10% of polyethylene glycol (PEG) 6000 solution. In this case, PEG 6000 solution was used as an osmotic selective barrier for pollen. After a little drying of the stigmas with PEG 6000 solution, pre-emasculated inflorescences of the *F*1 hybrid were pollinated with fresh pollen. The inflorescences moistened with distilled water were used for pollination in the control. One cm3 of pollen was taken for pollination of each head.

**Table 1** shows the percentages of germination in 10% PEG 6000 solution of *F*<sup>2</sup> seeds [22], obtained during pollen germination of *F*1 hybrid (ZL102 "*virescent*" x ZL9 "fan venation" crossing combination) in the presence and absence of osmotic on the stigmas of the hybrid plant.

As can be seen from the data presented in **Table 1**, the percentage of *F*2 seed germination under conditions of osmotic stress was significantly higher in the experimental *F*2 population, which was obtained after pollination with fresh pollen of the inflorescences moistened with 10% solution of PEG 6000. These results may indicate that such manipulation with a heterogeneous population of pollen from *F*1 hybrid was effective and resulted in drought resistance improvement of *F*2 sporophytic population, increasing there the number of drought-tolerant genotypes [23].

**Table 2** shows the genetic structure of *F*2 populations for "*virescent*" marker-trait. Change in the segregation for this marker-trait may indicate that the gene or genes, which determine the tested marker-trait, directly affect the drought tolerance of


## **Table 1.**

*Influence of pollen germination of F1 hybrid in vivo in the presence of osmotic on germination of F2 seeds in the medium with osmotic in sunflower.*


**Table 2.**

*Influence of pollen germination of F1 sunflower hybrid in vivo in the presence of osmotic on segregation ratio in F2 generation for "virescent" marker-trait.*

plants or are linked to the genes, which determine the plant resistance to osmotic stress and dry environmental conditions [24].

The results of marker analysis for «*virescent*» trait showed the modification in segregation for the experimental *F*2 population, which was obtained after germination of *F*1 hybrid pollen on the stigmas moistened with osmotic, compared to the control. This modification resulted in a significant increase in the number of plants with the "*virescent*" trait. As for "fan venation", differences in segregation ratio for this trait were not revealed. Therefore, we can state the fact of the shift in the genetic structure of *F*2 populations after carrying out gametophytic selection for drought tolerance which favored the survival of gametes with the "*virescent*" marker-trait and, at the same time, the elimination of gametes with an alternative trait.

In general, it must be admitted that pollination with a heterogeneous pollen population of stigmas moistened with the osmotically active substance can increase the drought resistance of *F*2 sporophytic populations and modify their genetic structure for some marker traits. Also, it should be noted, that the simultaneous rise in the drought resistance and in the number of plants with the "*virescent*" marker-trait in *F*2 population indicates that the gene or genes, which determine the "*virescent*" trait, directly influenced the drought resistance or were linked to the genes responsible for tolerance of pollen and plants to water stress.
